Elephant seal bibliography
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Adams, S. H. and D. P. Costa (1993). Water conservation and protein metabolism in northern elephant seal pups during the postweaning fast. J. Comp. Physiol. B 163(5): 367-373.
Urine production and N output were monitored in northern elephant seal (Mirounga angustirostris) pups progressing through 10 weeks of a natural post-weaning fast. Urine output declined by 84% (to 69 plus or minus 12 ml/day) at 10 weeks (P < 0.05). Glomerular filtration rate at 10 weeks was 51% of the 67 plus or minus 3 ml serum/min observed during week 1 (P < 0.05). Urine N excretion fell by 69% to 1.2 plus or minus 0.17 g/day, while urinary concentration increased (P < 0.05). Serum urea declined from an initial 11 mmol/l to 5-7 mmol/l by 5 weeks. The fall in urinary N loss (and thus amino acid oxidation) was concomitant with depressed metabolic rate. Therefore, protein contributed little toward meeting energy demands (i.e., < 4% of average metabolic rate) throughout fasting. These data indicate that fasting pups improve water conservation and minimize protein catabolism during prolonged natural fasts without an exogenous source of water.
Aguayo, L. A., M. P. Ibanez, G. M. Rauch and M. V. Vallejos (1995). Primer registro del elefante marino del sur, Mirounga leonina, en la Isla de Pascua, Chile, Instituto Antartico Chileno: 123-129.
Allen, S. G., S. C. Peaslee and H. R. Huber (1989). Colonization by northern elephant seals on the Point Reyes Peninsula, California. Marine Mammal Science 5(3): 298-302.
Northern elephant seals, Mirounga angustirostris , were hunted commercially for their oil in the early 1800s. By the early 1900s fewer than 100 survivors were concentrated on Isla de Guadalupe, Mexico. Stringent protection by the Mexican and United States governments allowed the population to recover: recolonization of the California offshore islands began in 1938. Subsequently, the elephant seal has made a remarkable recovery; based on the most recent census, numbers have reached an estimated 77,000 adults. Part of this recovery has included the colonization of the California mainland, but whether northern elephant seals historically bred on the mainland is not known. The first pup born on the mainland in this century was at Ano Nuevo Point in 1975. Since then pups have been reported at other mainland areas in California. Elephant seals were reported as far north as the Point Reyes Peninsula before exploitation; however, there is no evidence to indicate that a breeding colony existed there. Since the 1970s, northern elephant seals were sighted on beaches along the Point Reyes Peninsula with increasing frequency. The first pup was found on the Point Reyes Peninsula in 1976. However, it was not until 1981 that a colony formed at Point Reyes Headland, at a site different from where the first birth occurred.
Andrews, R. D., D. R. Jones, J. D. Williams, P. H. Thorson, G. W. Oliver, D. P. Costa and B. J. Le Boeuf (1997). Heart rates of northern elephant seals diving at sea and resting on the beach. Journal of Experimental Biology 200(15): 2083-2095.
Heart rates of northern elephant seals diving at sea and during apnoea on land were monitored to test whether a cardiac response to submergence is an important factor in their ability to make repetitive, long-duration dives. Seven juvenile northern elephant seals were captured at Año Nuevo, CA, instrumented and translocated to release sites around Monterey Bay. Heart rate and dive depth were recorded using custom-designed data loggers and analogue tape monitors during the seals’ return to Año Nuevo. Heart rates during apnoea and eupnoea were recorded from four of the seals after they hauled out on the beach. Diving patterns were very similar to those of naturally migrating juveniles. The heart rate response to apnoea at sea and on land was a prompt bradycardia, but only at sea was there an anticipatory tachycardia before breathing commenced. Heart rate at sea declined by 64 % from the surface rate of 107±3 beats min-1 (mean ± S.D.), while heart rate on land declined by 31% from the eupnoeic rate of 65±8 beats min-1. Diving heart rate was inversely related to dive duration in a non-linear fashion best described by a continuous, curvilinear model, while heart rate during apnoea on land was independent of the duration of apnoea. Occasionally, instantaneous heart rate fell as low as 3 beats min-1 during diving. Although bradycardia occurs in response to apnoea both at sea and on land, only at sea is heart rate apparently regulated to minimise eupnoeic time and to ration oxygen stores to ensure adequate supplies for the heart and brain not only as the dive progresses normally but also when a dive is abnormally extended.
Andrews, R. D. (1999). The cardiorespiratory, metabolic, and thermoregulatory physiology of juvenile northern elephant seals (Mirounga angustirostris). Department of Zoology, University of British Columbia.
Andrews, R. D., D. P. Costa, B. J. Le Boeuf and D. R. Jones (2000). Breathing frequencies of northern elephant seals at sea and on land revealed by heart rate spectral analysis. Respiration Physiology 123(1-2): 71-85.
Elephant seals breathe episodically at sea and on land and surprisingly long apnoeas occur in both situations. An important difference is that recovery from apnoeic periods is much quicker at sea, which might be due, in part, to differences in the ventilatory response. Respiratory frequencies of juvenile northern elephant seals diving at sea and resting on land were estimated from time-frequency maps of the Wigner distribution of heart rate variability. Simultaneous direct measurement of respiration and estimation of respiratory frequency (fR) in the laboratory demonstrated that the error of estimation was small (mean +/- S.D.= 1.05+/-1.23%) and was independent of the magnitude of fR. Eupnoeic fR at sea was 2.4 times higher than on land (22.0+/-2.0 vs. 9.2+/-1.3 breaths min(-1), respectively), facilitating quick recovery from the preceding dive and allowing a 34% increase in time spent apnoeic at sea versus on land. The overall fR (no. of breaths in a eupnoea divided by the total time of the apnoea+eupnoea cycle) of 2.3+/-0.6 breaths min(-1) at sea was no different from the rate on land and was inversely related to the preceding dive duration, suggesting that metabolism on longer dives may be reduced.
Angot, M. (1954). Observations sur le mammiferes marins de l' Archipel de Kerguelen. Mammalia 18: 1-111.
Antonelis, G. A., Jr., S. Leatherwood and D. K. Odell (1981). Population growth and censuses of the northern elephant seal, Mirounga angustirostris, on the California Channel Islands, 1958-78.
Antonelis, G. A., Jr., M. S. Lowry, D. P. DeMaster and C. H. Ficus (1987). Assessing northern elephant seal feeding habits by stomach lavage. Marine Mammal Science 3(4): 308-322.
Stomach lavaging was used to study the feeding habits of northern elephant seals (Mirounga angustirostris) found on San Miguel Island, California, during the spring of 1984. Fifty-nine elephant seals were chemically immobilized with an intramuscular injection of ketamine hydrochloride. Once immobilized, an animal’ s stomach was intubated, filled with 3-4 liters of water to create a slurry of the undigested food items, and evacuated into a collection device. The stomachs of 57 (96.6%) of the animals lavaged contained identifiable parts of prey. Twenty-nine different food items were identified, 12 of which have not been previously reported as prey of the northern elephant seal: two teleost fish, Coryphaenoides acrolepis (Pacific rattail) and another unidentified macrourid; two crustaceans, Pasiphaea pacifica (glass shrimp) and Euphausia sp.; six squid, Abraliopsis felis, Gonatus berryi, Histioteuthis dofleini, Cranchia scabra, Taonius pavo, and Galiteuthis sp. and two octopi, Octopus dofleini and Octopus rubescens. The following prey species were found in at least 20% of stomachs lavaged: Octopoteuthis deletron (squid), Merluccius productus (Pacific whiting), Gonatopsis borealis (squid), Pleuroncodes planipes (pelagic red crab), H. dofleini and H. heteropsis. The diversity of habitats in which many of these prey are commonly found indicates that the northern elephant seals from San Miguel Island are capable of foraging in a variety of marine environments (epipelagic, mesopelagic, bathypelagic, neritic and benthic) and may only be limited by the depth to which they can dive. Key words: Northern elephant seals, feeding habits, stomach lavage, ketamine immobilization.
Antonelis, G. A., M. S. Lowry, C. H. Fiscus, B. S. Stewart and R. L. Delong (1994). Diet of the northern elephant seal. Le Boeuf: opulation ecology, behavior, and physiology University of California Press Berkeley, Los Angeles etc 1994 i-xviii, 1-414 Chapter pagination 211-223.
Aretas, R. (1951). L' elephant de mer (Mirounga leonina L.). Etude biologique de l' espéce dans le possesions francaises australes (Archipel des Kerguelen). Mammalia 15: 105-117.
Arnbom, T. A., N. J. Lunn, I. L. Boyd and T. Barton (1992). Aging live Antarctic fur seals and southern elephant seals. Marine Mammal Science 8(1): 37-43.
This study describes a method for extracting post-canine or incisor teeth from live antarctic fur seals (Arctocephalus gazella ) and southern elephant seals (Mirounga leonina) respectively and their use to determine age in a field situation. Dental elevators were used to loosen the teeth from the alveolus and periodental ligament. Most teeth were removed within 1-2 min and a total of 214 and 81 teeth were collected by this method from antarctic fur seals and southern elephant seals respectively. No seal recaptured at intervals up to a year after a tooth was extracted showed signs of infection or distress related to removal of the tooth. Teeth were thin-sectioned for the purpose of aging. In both species cementum growth layer groups were a more satisfactory of age than dentinal growth layer groups. Estimates of age from cementum growth layers were confirmed for Antarctic fur seals using seals which had been tagged as pups up to 16 yr before sampling.
Arnbom, T., M. A. Fedak, I. L. Boyd and B. J. McConnell (1993). Variation in weaning mass of pups in relation to maternal mass, postweaning fast duration, and weaned pup behaviour in southern elephant seals (Mirounga leonina) at South Georgia. Canadian Journal of Zoology 71(9): 1772-1781.
Female southern elephant seals, Mirounga leonina, assemble in large groups and each gives birth to a single pup which is nursed for some 3 weeks. Weaning mass is highly variable; some pups are three times as heavy as others at weaning. After weaning, the pup fasts for several weeks before departing to sea. The function of this fast is unknown. We examined the relationships between maternal mass, pup weaning mass, and pup behaviour during the postweaning fast in 377 pups and 128 adult females over four breeding seasons at South Georgia. Pup weaning mass was positively related to maternal postpartum mass, which accounted for 55% of the variation in weaning mass. Over all 4 years male pups were significantly heavier at weaning than female pups (130 vs. 123 kg) but this difference disappeared after maternal mass was controlled for. After fasting for 21-66 days, weaned pups went to sea at an average of 68% of weaning mass. Heavier pups remained on the beach longer after weaning than lighter pups. There was no evidence that pups synchronized their departure to sea. Only male pups were observed to take part in mock fights. With increasing age, weaned pups spent more time in the water. Mortality during the postweaning fast was negligible (0.1%). The timing of departure of weaned pups may involve a trade-off between an early departure with greater fat (energy) stores but poorer foraging ability and a late departure with increased swimming, diving, and social skills but reduced fat stores.
Arnbom, T. (1994). Maternal investment in male and female offspring in the southern elephant seal. Department of Zoology. Stockholm, Stockholm University.
Arnbom, T., M. A. Fedak and P. Rothery (1994). Offspring sex ratio in relation to female size in southern elephant seals, Miorunga leonina. Behavioral Ecology and Sociobiology 35: 373-378.
Southern elephant seals Mirounga leonina display extreme sexual dimorphism. In addition females show great variation in size and stored resources at parturition. Therefore they present an excellent opportunity for examination of responses of sex ratio to resource availability. We studied the relationships between the size of southern elephant seal females at parturition and the size and sex of their pups at South Georgia over four breeding seasons. We found a large individual variation in maternal post-partum mass (range 296-977 kg, n=151). Larger mothers gave birth to larger pups, irrespective of the sex of their pup. Male pups were on average 14% larger than females at birth and consequently more costly to bring to parturition. Our results suggest that female southern elephant seals must weigh more than 300 kg if they are to breed at all, and more than 380 kg if they are to give birth to a male pup. Above this threshold the proportion of males among offspring rapidly increases with maternal mass, and stabilizes at a level not significantly different from parity. These results show that smaller females of southern elephant seals vary offspring sex ratio in a way that is consistent with theories on adaptive offspring sex ratio. A smaller mother with a male foetus may benefit from terminating her pregnancy and allocating the resources she saves to her own growth. She could then give birth to and raise a larger pup in the subsequent season.
Arnbom, T. and S. Lundberg (1995). Notes on Lepas australis (Cirripedia, Lepadidae) recorded on the skin of southern elephant seal (Mirounga leonina). Crustaceana 68( 5): 655- 658.
Here we report observations of L. australis, all attached to the skin of the dorsal side of four different live breeding southern elephant seals (Mirounga leonina (Linnaeus, 1758)) females during October and November in 1989, 1990 and 1993 at Husvik, South Georgia (54 degree 10'S 36 degree 43'W). Two adult specimens of L. australis were collected in 1990 and are now preserved at the Swedish Museum of Natural History, Stockholm (collection number 1425, fig. 1). The sizes of the capitulum of the collected specimens were 18 mm and 21 mm, respectively, which is similar to the breeding size reported by MacIntyre (1966). The numbers of observed Lepas specimens on the four different individual seals were 2, 2, 2, and 1, respectively. The Lepas specimens which were not collected had a similar size to the ones collected, and they had disappeared from the live seals after 2-3 days ashore.
Arnbom, T., A. Modig, I. L. Boyd and M. A. Fedak (1995). Behavior, and mass changes during breeding in male southern elephant seals at South Georgia. World Marine Mammal Science Conference Orlando, Florida, Lawrence, KS, Society for Marine Mammalogy.
The body energy stores southern elephant seal (Mirounga leonina) males bring ashore for the fast on land, is most likely a factor influencing high hierarchy rank, length of stay on land and perhaps behavioural activity. Behaviour activity, mass and mass changes of individual southern elephant seal males of different ranks (harem masters, peripheral, outside) were studied during 1988-1993 breeding seasons at South Georgia. South Atlantic Ocean. Mass and mass changes were collected by using a weighing platform.
The most common behaviour for males of all ranks was resting(>80%) . Males outside harems spent more time resting than males inside harems. Peripheral males spent more time on aggresive behaviour than harem masters. Mass varied between 950-2772 kg (N=60), and males of higher rank weighed more than males of lower rank. Mass changes for individual males varied between 7-19 kg/d (n=6). Harem masters and peripheral males lost 30-34 % (N=4) of total body mass while two outside males lost 20% and 23%, respectively. The largest male lost about 1050 kg (32%) during 73 days on land.
The behavioural activity and mass changes seem to follow each other with small males outside the harems spending more time resting and depleting relatively less of its body energy stores, than males residing inside the harems. Peripheral males, which defend the flanks of larger harems, had a lower reproductive success despite spending more time being aggressive and lost relatively more body mass than harem masters.
Arnbom, T., M. A. Fedak and I. L. Boyd (1997). Factors affecting maternal expenditure in southern elephant seals during lactation. Ecology 78(2): 471-483.
Southern elephant seals Mirounga leonina provide a unique opportunity for examination of parental investment because postpartum pup growth is fueled exclusively by energy from stored reserves in fasting mothers, and the seals are extremely sexually dimorphic as adults. We examined the influence of pup sex, maternal size, and other factors on the variation in postpartum maternal mass change and pup growth. Elephant seals (178 mothers and 445 pups) were weighed during four breeding periods at South Georgia Island. Maternal mass change during lactation increased markedly with the mass of the mother at parturition. Postpartum maternal mass accounted for 75% of the variation in mass loss and 62% of the variation of pup mass at weaning. Size of the pup at birth explained <4% of this variation, and the sex of the pup explained virtually none (<0.1%). The duration of lactation was positively correlated with the pstpartumo mass of mothers, but negatively correlated with the rate of maternal mass loss when corrected for the effect of maternal postpartum mass. Mothers giving birth late in the season had shorter lactation periods than those that gave birth early but seemed to compensate for this by increasing the rate of mass transfer. Average transfer efficiency (pup mass gain/maternal mass loss) was 46 +/- 0.5%. Mothers lost, on average, 35% of their postpartum mass during lactation and 40% during the whole breeding period. Females whose postpartum mass increased between seasons increased their expenditure on their pups; females whose postpartum mass decreased, decreased their expenditure. These data from mothers with single pups do not clarify whether differences in investment were controlled by mothers or their offspring. However on three occasions, study females raised two pups in a season. Despite the increased demand, these females did not increase their expenditure, suggesting that levels of investment are maternally controlled. These results show that levels of expenditure in southern elephant seals appear to be determined largely by a single variable: female mass at parturition.
Asaga, T., Y. Naito, B. J. Le Boeuf and H. Sakurai (1994). Functional analysis of dive types of female northern elephant seals. Le Boeuf: opulation ecology, behavior, and physiology University of California Press Berkeley, Los Angeles etc 1994 i-xviii, 1-414 Chapter pagination 310-327.
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Baird, R. W. (1990). Elephant seals around southern Vancouver island. The Victoria Naturalist 47(2): 6-7.
Bajard, P. (1962). L' Eléphant de mer (Mirounga leonina). Biologie. Exploitation industrielle du troupeau hote de l' archipel de Kerguelen. Lion, France, Université de Lion.
Baker, J. R., S. S. Anderson and M. A. Fedak (1988). The use of a ketamine-diazepam mixture to immobilise wild grey seals (Halichoerus grypus) and southern elephant seals (Mirounga leonina). Vet. Rec. 123(11): 287-289.
A mixture of ketamine and diazepam, at doses of 6 mg/kg and 0.30 mg/kg respectively, proved to be a reliable and reasonably safe immobilisation agent for field work on grey and southern elephant seals. It was better than previously reported drugs used either singly or in combination.
Baldi, R., C. Campagna, S. Pedraza and B. J. Le Boeuf (1996). Social effects of space availability on the breeding behaviour of elephant seals in Patagonia. Animal Behaviour 51(4): 717-724.
The Patagonian breeding colony of southern elephant seals, Mirounga leonina, of Peninsula Vald6és, Argentina is characterized by long, continuous, homogeneous and spacious beaches. Reproduction in this colony occurs at the lowest group densities reported for the species. The availability of ample space resulted in the dispersion of reproductive females along 160 km of coastline, with a range of 0-300 reproductive individuals per km. Females grouped together in small harems (median=11 females, range 2-122, N=432), and individual distance between females was one to two female body lengths. Body contact within the harem was rare. Consequently, agonistic interactions (AIs) between females and female aggression (Ag) towards alien pups occurred inrrequenlly (median rate=4 AIs/female per lO0 h and 1 Ag/pup per 100 h, respectively). Pup mortality rate was low for an elephant seal rookery (3.5% for 3487 pups). Most dead pups were stillborn, and only three of 38 pups whose cause of mortality could be determined died from trauma or starvation following mother-pup separation. Female dispersal allowed many males to have access to females. About 45% of all males of reproductive size in the colony (about 1000 individuals) had a harem. Most adult males mated with receptive females. Low-density breeding conditions benefited female reproductive success through an increase in pup survival Female dispersal resulted in small harem size, however, and limited the potential for polygyny.
Baraj, B., A. Bianchini, L. F. H. Niencheski, C. C. R. Campos, P. E. Martinez, R. B. Robaldo, M. M. C. Muelbert, E. P. Colares and S. Zarzur (2001). The performance of ZEISS GFAAS-5 instrument on the determination of trace metals in whole blood samples of southern elephant seals (Mirounga leonina) from Antarctica. Fresenius Environmental Bulletin 10(12): 859-862.
Barrat, A. and J. L. Mougin (1978). L' eléphant de mer Mirounga leonina de l' île de la Possession, archipel Crozet (46°25' S, 51°45' E). Mammalia 42(2): 143-174.
Evoluzione temporale della demografia della popolazione [149-159]
Ciclo riproduttivo annuale della popolazione [159-166]
Variazione del sex ratio nel corso della fase riproduttiva [167-168]
Conclusioni [169-171]
Bartholomew, G. A. (1952). Reproductive and social behavior of the northern elephant seal. Univ. Calif. Publ. Zool. 47: 369-472.
Bartholomew, G. A. and A. Boolootian (1960). Numbers and population structure of the Pinnipeds on the California Channel Islands. Journal of Mammalogy 41(3): 366-375.
Bartholomew, G. A. and C. L. Hubbs (1960). Population growth and seasonal movements of the northern elephant seal, Mirounga angustirostris. Mammalia 24: 313-324.
Bartholomew, G. A. and N. E. Collias (1962). The role of vocalization in the social behaviour of the Northern Elephant Seal. Animal Behaviour 10(1): 7-14.
Beckmen, K. B., L. J. Lowenstine, J. Newman, J. Hill, K. Hanni and J. Gerber (1997). Clinical and pathological characterization of northern elephant seal skin disease. Journal of Wildlife Diseases 33(3): 438-449.
From 1984 through 1992, staff at The Marine Mammal Center (TMMC, Sausalito, California, USA) examined 207 northern elephant seals (Mirounga angustirostris) with a condition of unknown etiology called northern elephant seal skin disease (NESSD). The skin lesions were characterized by patchy to extensive alopecia and hyperpigmentation, punctate or coalescing epidermal ulceration, and occasionally, massive skin necrosis. Microscopic lesions included ulcerative dermatitis with hyperkeratosis, squamous metaplasia and atrophy of sebaceous glands. All diseased seals were less than 2 years of age and suffered from emaciation, depression, and dehydration. Mortality from septicemia increased significantly with severity of skin ulceration. Compared to 14 apparently unaffected seals, diseased seals had depressed levels of circulating thyroxine, triiodothyronine, retinol, serum iron, albumin, calcium, and cholesterol. Levels of alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, gamma glutamyl transpeptidase, blood urea nitrogen, and uric acid were elevated. Morphometrically, diseased animals were approximately 15% smaller than normal seals of the same sage. Serum and blubber concentrations of 36 polychlorinated biphenyl congeners (sigma PCB) and dichloro-diphenyl-dichloroethylene (p,p'-DDE) were negatively correlated with body mass. Mean concentrations of sigma PCB and p,p'-DDE in serum in diseased seals were elevated as compared to apparently normal seals. Etiology of this syndrome remains unknown, but the possibility of PCB toxicosis cannot be ruled out.
Keywords: Alopecia, Biopsy, California, Cohort Studies, Prospective Studies, Retrospective Studies, Seals, Sebaceous Glands, Skin, Skin Diseases, Skin Ulcer
Bell, C. M., H. R. Burton and M. A. Hindell (1997). Growth of southern elephant seals, Mirounga leonina, during their first foraging trip. Australian Journal of Zoology 45(5): 447-458.
A longitudinal study of growth of southern elephant seals, Mirounga leonina, during their first foraging trip was undertaken at Macquarie Island. On average, body mass increased by 75% while foraging at sea, with individuals growing at 0.34 +/- 0.12 (s.d.) kg day(-1) (n = 64), and spending 182 +/- 51 days (n = 64) at sea. Relatively smaller changes in body length were recorded during the same period, suggesting that growth was composed primarily of adjustments to body composition, rather than increases in gross body size. This may be in response to the functional demands of pelagic life. Body size established early in life (birth mass and departure mass) positively influenced body mass upon return from the first foraging trip. Growth rate, however, was negatively related to departure mass for females, and this is hypothesised to be related to sex differences in body composition, as well as intrasex differences in foraging skills, diving ability and food-conversion efficiency. Despite this, there was no detectable age-specific sexual dimorphism in the first year of life. Animals that were at sea longer tended to return in better body condition. Interspecific comparison suggests that southern elephant seals grow more than do northern elephant seals, Mirounga angustirostris, and this difference may be related to prey abundance and distribution.
Bell, C. M., M. A. Hindell and H. R. Burton (1997). Estimation of body mass in the southern elephant seal, Mirounga leonina, by photogrammetry and morphometrics. Marine Mammal Science 13(4): 669-682.
A simple photographic technique was developed to indirectly estimate body mass data for southern elephant seal (Mirounga leonina) cows (postlactation), yearlings, and immature males and females. Regressions of mass on both photographic and morphometric variables (together and separately) yielded useful, predictable models. Using such variables, the best estimation of the actual mass was for postlactation cows, with a 95% confidence interval of +/- 2.66% of the predicted body mass. Although combining photographic and morphometric variables produced the most reliable models specifically for cows and yearlings, the most practical model contained only the morphometric variables length and girth squared. Side area was the best correlated single photographic variable and this corresponded with other studies. Photogrammetry could be useful when animals cannot be sedated and are located on a flat surface, but it does require animals to be motionless when approached. Thus, the procedure may be more suited to bulls rather than other age classes and could have a role in studies where large numbers of mass estimations are rapidly required. If sedation is utilized in smaller animals, then the use of body length and girth is the most suitable indirect mass estimation technique to avoid the use of heavy weighing equipment.
Bennett, K. A., B. J. McConnell and M. A. Fedak (2001). Diurnal and seasonal variations in the duration and depth of the longest dives in southern elephant seals (Mirounga leonina): Possible physiological and behavioural constraints. Journal of Experimental Biology 204(4): 649-662.
This study seeks to understand how the physiological constraints of diving may change on a daily and seasonal basis. Dive data were obtained from southern elephant seals (Mirounga leonina) from South Georgia using satellite relay data loggers. We analysed the longest (95th percentile) dive durations as proxies for physiological dive limits. A strong, significant relationship existed between the duration of these dives and the time of day and week of year in which they were performed. The depth of the deepest dives also showed a significant, but far less consistent, relationship with local time of day and season. Changes in the duration of the longest dives occurred irrespective of their depth. Dives were longest in the morning (04:00-12:00h) and shortest in the evening (16:00-00:00h). The size of the fluctuation varied among animals from 4.0 to 20.0 min. The daily pattern in dive depth was phase-shifted in relation to the diurnal rhythm in dive duration. Dives were deeper at midday and shallower around midnight. Greater daily changes in duration occurred in seals feeding in the open ocean than in those foraging on the continental shelf. The seasonal peak in the duration of the longest dives coincided with austral midwinter. The size of the increase in dive duration from autumn/spring to winter ranged from 11.5 to 30.0 min. Changes in depth of the longest dives were not consistently associated with particular times of year. The substantial diurnal and seasonal fluctuations in maximum dive duration may be a result of changes in the physiological capacity to remain submerged, in addition to temporal changes in the ecological constraints on dive behaviour. We speculate about the role of melatonin as a hormonal mediator of diving capability.
Best, P. B., M. A. Meyer and R. W. Weeks (1981). Interactions between a male elephant seal Mirounga leonina and Cape fur seals Arctocephalus pusillus.
A male elephant seal Mirounga leonina at Van Reenen Bay, South West Africa/Namibia, was observed catching, killing and attempting copulation with female fur seals Arctocephalus pusillus , as well as catching and occasionally killing fur seal pups and participating in territorial disputes with fur seal bulls. Previous and subsequent records of a similar-sized elephant seal in the same vicinity suggest that an individual male has adapted its annual reproductive haul-out to coincide with the fur seals' breeding season.
Best, N. J., C. J. A. Bradshaw, M. A. Hindell and P. D. Nichols (2003). Vertical stratification of fatty acids in the blubber of southern elephant seals (Mirounga leonina): implications for diet analysis. Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology 134(2): 253-263.
Fatty acid signature analysis (FASA) is a powerful ecological tool that uses essential fatty acids (FA) from the tissues of animals to indicate aspects of diet. However, the presence of vertical stratification in FA distribution throughout blubber complicates the application of FASA to marine mammals. Blubber biopsy samples were collected from adult female southern elephant seals (Mirounga leonina) from Macquarie Island (n=11), and blubber cores were divided into inner and outer sections to determine the degree to which the blubber layer was stratified in FA composition, we found 19 FA from both blubber layers in greater than trace amounts (>0.5%). The inner and outer blubber layers could be separated using principal components analysis based on the relative proportion of FA in each layer. Dietary polyunsaturated fatty acids (PUFA) were also observed in significantly higher proportions in the inner blubber layer. Due to the degree of FA stratification in southern elephant seals, we concur with other marine mammal studies that sampling only the outer blubber layer will result in a loss of recently accumulated information regarding diet structure (as indicated by `surplus' PUFA from the diet). This finding suggests that differential mobilization/deposition of certain FA may result in a modified signature from prey to predator. Thus, sampling animals to recover the inner blubber layer is important for studies attempting to describe aspects of marine mammal diet. This can be achieved in animals such as pinnipeds where the whole blubber layer can be readily sampled.
Bester, M. N. (1980 b). The southern elephant seal Mirounga leonina at Gough Island. South African Journal of Zoology 15(4): 235-239.
Southern elephant seals selected mainly the gently sloping, smooth-surfaced beaches and vegetated areas of the sheltered north-east coast. Mainly adults hauled out during the spring breeding season, with all pups being born by late October and the majority of the pups dispersing from their birthsites by December. Subadults were most abundant at the onset of the summer moult haul-out, with bulls and some subadult males being most abundant towards the end of the moulting season. During the 1977/78 summer, total population was estimated at 163 suggesting a slight decrease since 1955/56. Harems were small and few in number, and pregnant cows showed fidelity to previous pupping sites. Spatial and temporal separation of the breeding populations of elephant and fur seals precluded competition for haul-out sites.
Bester, M. N. and P. Y. Lenglart (1982). An analysis of the southern elephant seal Mirounga leonina breeding population at Kerguelen. South African Journal of Antarctic Research 12: 11-16.
The spring 1979 breeding population of southern elephant seals at Kerguelen numbered 2,993 bulls and 38,181 cows, with 36,291 live pups present during the census period. Significant differences in the overall sex ratio, harem structure and frequency distribution exist in comparison with previous surveys. These differences may be related to the difference in the mean census dates of the different years, but were also accompanied by a continued decrease in both the cow and bull components, corroborating the slump noted since 1970. An analysis based on subdivisions of the study area into distinct regions showed area specific increases and decreases in cow numbers, in spite of the net decrease in cow numbers. The linear regression of area specific percentage pup mortality on the density of cows was highly significant, which could explain the area specific fluctuation in cow numbers, elephant seal cows reputedly showing fidelity to their birthsites.
Bester, M. N. (1988). Marking and monitoring studies of the Kerguelen stock of southern elephant seals Mirounga leonina and their bearing on biological research in the Vestfold Hills. Hydrobiologia 165: 269-277.
Southern elephant seals Mirounga leonina breed and moult on many subantarctic islands during the austral spring and summer. In the Kerguelen Province the subpopulations of M. leonina at Kerguelen, Marion, and Possession islands have declined since 1970 and their present status at Heard I. is unknown. Population studies during their terrestrial phase have failed to explain the declines. Long distance movements of individuals between the subpopulations in question and also the Vestfold Hills have been recorded. The availability of food resources, competition with rapidly increasing fur seal populations and competition with fishing fleets have all been implicated in their decline. These explanations assume that communal feeding grounds are utilized. As they are predators entirely dependent on marine feeding, a study of their spatial and temporal distribution during their pelagic existence is of the utmost importance. Parameters describing growth, reproduction rates, population dynamics, and feeding ecology of the subpopulations in the Kerguelen Province may furthermore serve as indices of change within the marine ecosystem. The presence of a relatively large and predominantly male nonbreeding population of M. leonina at the Vestfold Hills which originates from the Kerguelen/Heard Island group, and which shows annual return, should be included in the marking and monitoring studies of the Kerguelen stock of southern elephant seals. Studies here include an update of the size and social structure of the Heard Island subpopulation.
Bester, M. N. and D. G. M. Miller (1988). Southern elephant seals and CCAMLR. Hobart, Tasmania, Scientific Committee for the Conservation of Antarctic Marine Living Resources.
This paper describes research findings of studies on the southern elephant seal (Mirounga leonina) in Kerguelen Is. and vicinity. Sub-populations of this species have declined at Kerguelen, Marion, Prince Edward and Heard islands. Population studies during the animals' terrestrial phase have failed to explain this observed decline which has also been recently confirmed for the Macquarie I. stock. The availability of food, competition with rapidly growing fur seal populations and competition with fishing fleets have all been suggested as possible causes of the elephant seal's decline in the region. Such explanations assume that a communal feeding ground, not yet identified, exists and that this exerts some common influence on the species' population dynamics. (Auth. mod.)
Bester, M. N. (1988). Chemical restraint of antarctic fur seals and southern elephant seals. S. Afr. J. Wildl. Res. 18(2): 57-60.
Antarctic fur seal, Arctocephalus gazella, yearlings (n=14) and southern elephant seal, Mirounga leonina, cows (n=5) were injected with a combination (5:1) of ketamine hydrochloride and xylazine hydrochloride. Effective immobilization of elephant seals was achieved with dosages of 3.6-6.4 mg ketamine/kg body mass, while 3.8-6.6 mg ketamine/kg body mass were required for fur seals. No correlation existed between the dosage and induction time nor degree of effect of the drugs. The level of activity or arousal of the seals prior to the administration of the drug influenced their tolerance, although individual variation seemed to exist. Ketamine doses above 5.6 mg/kg body mass invariably immobilized both groups of seals.
Bester, M. N. (1989). Movements of southern elephant seals and subantarctic fur seals in relation to Marion Island. Marine Mammal Science 5(3): 257-265.
Based primarily on an intensive marking/resighting program conducted at Marion Island in the Southern Ocean, the inter-island movements of southern elephant seals, Mirounga leonina , and fur seals Arctocephalus spp., were investigated to elucidate their little known pelagic phase. Southern elephant seals, in particular immature animals, readily move between the proximate Marion and Prince Edward islands. Some range as far afield as Iles Crozet, approximately 1,000 km distant where they haul out for the summer molt or during an autumn resting phase. The exchange of individuals between Marion Island and Iles Crozet during the return of immatures for the molt after a winter at sea, suggests overlapping of the foraging ranges of the two populations. Despite their wanderings, the majority of M. leonina from Marion Island probably feed in the proximity of the island, and relocate onto the island for breeding, molting and resting. Of the fur seals, only a few A. tropicalis were seen away from their natal island, in some cases covering distances in excess of 2,000 km, displaying a remarkable dispersal capacity.
Bester, M. N. (1990). Population trends of subantarctic fur seals and souther elephant seals at Gough Island. S. Afr. J. Antarct. Res. 20(1): 9-12.
The subantarctic fur seal (Arctocephalus tropicalis) population at Gough I. in the South Atlantic Ocean is continuing to increase rapidly since its recovery from exploitation. The intrinsic rate of increase is however slowing down on established breeding colony beaches in the western sector as congested conditions develop. The rate of increase on the more recently colonized breeding colony sites on the east coast is high, but some beaches here remain unexploited by breeders despite the increased density on the west coast. The small breeding population of southern elephant seals (Mirounga leonina) either has remained stable, or declined very slowly, over the past 17 years.
Bester, M. N. and H. M. Pansegrouw (1992). Ranging behaviour of southern elephant seal cows from Marion Island. South African Journal of Science 88(11-12): 574-575.
Southern elephant seals, Mirounga leonina, comprising the South Georgia, Macquarie and Kerguelen stocks, breed and moult on islands on both sides of the Antarctic Polar Front (APF). In the Kerguelen Province the subpopulations of M. leonina hauling out at Heard Island, Iles Kerguelen, Marion Island and Ile de la Possession are declining and terrestrial studies have failed to explain the reason(s) for the declines. As the fall in the southern elephant seal population at Marion Island appears to be influenced by factors affecting the survival of immature and young adult cows which feed only while at sea, investigating the pelagic phase of their life cycle is the most important priority. The present study showed that adult cows range widely and appear to concentrate their feeding at oceanic frontal systems.
Bester, M. N. and I. S. Wilkinson (1994). Population ecology of southern elephant seals at Marion Island. Elephant seals. Population ecology, behavior and physiology. B. J. L. B. R. M. Laws. Berkeley (CA), Un. California Press: 85-97.
Research has highlighted the continued decline in the southern elephant seal population at Marion Island, and life table data implicate recently matured cows as the most vulnerable part of the population. Observation on onshore behavior suggests that the factors producing the levate mortality rates of these cows operate at sea. Current research is concentrated on the investigation of at-sea behavior of this component of the population.
Bester, M. N., H. Moller, J. Wium and B. Enslin (2001). An update on the status of southern elephant seals at Gough Island. South African Journal of Wildlife Research 31(1-2): 68-71.
A slow decline in the small breeding population of southern elephant seals (Mirounga leonina) at Gough Island appears to have taken place over a period of 25 years (1973-1998). The estimated number of births has declined from a high of 38 in 1975 to a low of 11 in 1997. The remaining population is vulnerable; especially during the breeding season in spring, and human disturbance should be limited, in particular during the annual relief of the South African meteorological team stationed at the island.
Biuw, M., B. McConnell, C. J. Bradshaw, H. Burton and M. Fedak (2003). Blubber and buoyancy: monitoring the body condition of free-ranging seals using simple dive characteristics. J Exp Biol 206(Pt 19): 3405-23.
Elephant seals regularly perform dives during which they spend a large proportion of time drifting passively through the water column. The rate of vertical change in depth during these "drift" dives is largely a result of the proportion of lipid tissue in the body, with fatter seals having higher (more positive or less negative) drift rates compared with leaner seals. We examined the temporal changes in drift rates of 24 newly weaned southern elephant seal (Mirounga leonina) pups during their first trip to sea to determine if this easily recorded dive characteristic can be used to continuously monitor changes in body composition of seals throughout their foraging trips. All seals demonstrated a similar trend over time: drift rates were initially positive but decreased steadily over the first 30-50 days after departure (Phase 1), corresponding to seals becoming gradually less buoyant. Over the following approximately 100 days (Phase 2), drift rates again increased gradually, while during the last approximately 20-45 days (Phase 3) drift rates either remained constant or decreased slightly. The daily rate of change in drift rate was negatively related to the daily rate of horizontal displacement (daily travel rate), and daily travel rates of more than approximately 80 km were almost exclusively associated with negative changes in drift rate. We developed a mechanistic model based on body compositions and morphometrics measured in the field, published values for the density of seawater and various body components, and values of drag coefficients for objects of different shapes. We used this model to examine the theoretical relationships between drift rate and body composition and carried out a sensitivity analysis to quantify errors and biases caused by varying model parameters. While variations in seawater density and uncertainties in estimated body surface area and volume are unlikely to result in errors in estimated lipid content of more than +/-2.5%, variations in drag coefficient can lead to errors of >or =10%. Finally, we compared the lipid contents predicted by our model with the lipid contents measured using isotopically labelled water and found a strong positive correlation. The best-fitting model suggests that the drag coefficient of seals while drifting passively is between approximately 0.49 (roughly corresponding to a sphere-shaped object) and 0.69 (a prolate spheroid), and we were able to estimate relative lipid content to within approximately +/-2% lipid. Our results suggest that this simple method can be used to estimate the changes in lipid content of free-ranging seals while at sea and may help improve our understanding of the foraging strategies of these important marine predators.
Blackwell, S. B., B. J. Le Boeuf, D. E. Crocker and P. M. Webb (1995). Hold your breath and stay fat: an estimate of the water savings from terrestrial apnea in the weanling northern elephant seals. World Marine Mammal Science Conference Orlando, Florida, Lawrence, KS, Society for Marine Mammalogy.
Blackwell, S. B. (1997). Terrestrial apnea in northern elephant seals, Mirounga angustirostris: development and role in water economy. Department of Biology. Santa Cruz, California, University of California Santa Cruz.
Blackwell, S. B., C. A. Haverl, B. J. Le Boeuf and D. P. Costa (1999). A method for calibrating swim-speed recorders. Marine Mammal Science 15(3): 894-905.
During the last decade time-depth recorders (TDRs) have been deployed on a majority of pinniped species as a means of studying their diving behavior and foraging ecology. Our aim in the present paper is to: (1) present the theoretical framework for a calibration method for flow-driven swim-speed recorders, and (2) render this method easily useable with large TDR data sets by developing an automatic computerized calibration program for general use. The method involves comparing revolutions per minute (rpm) from the turbine of a swim-speed TDR with changes in depth measured by the instrument's calibrated pressure transducer. The subject collects the data for calibrating the instrument it bears, minimizing errors having to do with variation in animal size, shape (i.e., interindividual and interspecific differences) and instrument position. We used a total of 46 diving records from two species of pinnipeds: Northern elephant seals, Mirounga angustirostris, from Ano Nuevo, California (n = 33), and Hooker sea lions, Phocarctos hookeri, from Enderby Island, New Zealand (n = 13). The method we have described constitutes a fast and conceptually simple way of calibrating swim-speed recorders that reduces errors due to variation in subject size or position of the instrument on the animal. It has been tested in both phocids and otariids, which have very different swimming modes. When used prudently, this method should facilitate the acquisition of new information on foraging behavior, diving energetics, and the development of diving.
Boltnev, A. I. and A. E. York (2001). Maternal investment in northern fur seals (Callorhinus ursinus): interrelationships among mothers' age, size, parturition date, offspring size and sex ratios. Journal of Zoology 254: 219-228.
The analysis of life-history traits suggests that the age and size of female mammals at parturition will affect the birth size and survival of their offspring. We collected data from 252 mother-pup pairs of northern fur seals on Bering Island, Russia, during the 1994 and 1996 breeding seasons to determine the interrelationships among the mothers' age and mass, the sex of the pup, the parturition date, and the length and mass of the pup at birth. Among reproductive females of 19 years, mass increased with age. The mean mass of the oldest class of females (20-23 years) was lighter than the 16-19 year age group but not different from the mean mass of the 7- to 15-year-old females; a quadratic model of mass on age gave similar results, and indicated a maximum mass at age 19 years. We suggest that this may be an effect of a higher rate of survival among leaner animals. Female pups were lighter than males at birth. There was no evidence that the sex ratio of pups differed from 1:1 over the range of observed mothers' mass and age or parturition dates. Older mothers tended to give birth earlier than younger mothers, and heavier mothers earlier than lighter mothers. The relationship of the size of pups at birth and their mothers' age was adequately described with a quadratic model, which predicted a maximum size for mothers at age 12-13 years. The size of pups at birth and the size of their mothers was described with a logistic model which predicted that the size of pups increased for mothers up to 41 kg, with no further increase for heavier mothers. The total amount of variability in birth size explained by the combined models is < one-third of the total, which implies that other influences, such as the contribution of the fathers and individual variation, are also important. The relative maternal investment, measured as the ratio of pup mass to mothers' mass, ranged from 20% for younger and smaller females to 10% for older and heavier females. In addition, relative maternal investment was found to be higher than for other pinnipeds.
Bonnell, M. L. and R. K. Selander (1974). Elephant seals: genetic variation and near extinction. Science 184: 908-909.
Bornemann, H., J. Plotz, S. Ramdohr and L. Sellmann (1998). Southern elephant seal migration and Antarctic sea ice. Berichte zur Polarforschung 299: 168-173.
Bornemann, H., M. Kreyscher, S. Ramdohr, T. Martin, A. Carlini, L. Sellmann and J. Plotz (2000). Southern elephant seal movements and Antarctic sea ice. Antarctic Science 12(1): 3-15.
Boveng, P., D. P. DeMaster and B. S. Stewart (1988). Dynamic response analysis. 3. A consistency filter and application to four northern elephant seal colonies. Marine Mammal Science 4( 3): 210- 222.
Dynamic response analysis, a technique for determining stock size relative to the maximum net productivity level (MNPL), was applied to northern elephant seal populations from the South Farallon Islands, Ano Nuevo Island, San Nicolas Island and San Miguel Island. Pup counts were used as indices of population size. The application of dynamic response analysis presented here involved some methodological innovations. The authors present a moving interval method which involves calculating separate dynamic response analyses for intervals of various lengths ranging from four counts to the total number available for the colony.
Boyd, I. L. and T. Arnbom (1991). Diving behaviour in relation to water temperature in the southern elephant seal: foraging implications. Polar Biology 11(4): 259-266.
Boyd, I. L. (1993). Selecting sampling frequency for measuring diving behavior. Marine Mammal Science 9(4): 424-430.
This paper evaluates, using examples from the diving records of a southern elephant seal and an antarctic fur seal, the degree to which intervals between sampling affects the ability to identify dives, and the ultimate effect this has on the descriptive statistics of diving behavior. Southern elephant seals are deep (300-500 m), long (15-30 min), and continuous divers, whereas antarctic fur seals are shallow (15-30 m) and short (1-2 min) divers with dives occurring in bouts broken by variable periods at the surface. These species represent the extremes of diving patterns in pinnipeds. Wildlife Computers Mk III TDRs were used with a single data sampling protocol. Intervals between sampling of 5 and 10 sec were used for the fur seal and the elephant seal respectively, which are 2-9 times shorter than commonly used sampling intervals.
Boyd, I. L., T. Arnbom and M. Fedak (1993). Water flux, body composition, and metabolic rate during molt in female southern elephant seals (Mirounga leonina). Physiol. Zool. 66(1): 43-60.
Tritiated water dilution was used to measure changes in the proximate body composition of adult female southern elephant seals at the end of lactation and at the beginning and end of molt. During the 72 d foraging phase between lactation and molt, seals gained 1.50 kg/d. Of the total mass gain, 49% was water, 39% was fat, and 11% was protein. This represented an increase in total body gross energy of 2,111 MJ throughout the foraging period. The rate of mass lost during molt was 4.70 kg/d comprising 49% water, 33% fat and 16% protein. Although it was impossible to measure accurately the duration of fasting during the molt, the minimum cost of molt was 1,631 MJ, which was not significantly different from the energy gained between lactation and molt. Females invested half as much in molt as in the growth of their pups. The metabolic rate during molt was 2.15 W/kg, which was 2.8 times the predicted resting metabolic rate. Water influx was greater than expected from metabolic water production, and seals had an additional water influx of 1.75 L/d. This additional influx was negatively related to metabolic water production. There was some evidence from measurements of water influx that seals fed during molt, but this accounted for only 11.5% of the daily energy expenditure.
Boyd, I. L., T. A. Arnbom and M. A. Fedak (1994). Biomass and energy consumption of the South Georgia populations of elephant seals. Elephant seals. Population ecology, behavior and physiology. B. J. L. B. R. M. Laws. Berkeley (CA), University of California Press: 98-117.
The total annual energy expenditure was estimated for different age and sex classes of southern elephant seals, Mirounga leonina, that breed at South Georgia. The estimated energy costs of reproduction, growth, foraging, and molt were used to calculate an annual energy budget for individuals in each age and sex class. This was combined with population size and age structure to estimate population energy requirements. The estimated average metabolic cost of maintenance for adult males and females was 0.1 7 and 0.39 MJ/year, respectively. Male biomass accounted for 63% of the total population biomass (222,903 metric tonnes), and the metabolic power for the whole population averaged over one year was 190 MWatts. Total energy expenditure of each age class declined during the rirst two years but then began to increase because of the onset of reproduction in females and because of increased energy costs of foraging and growth in males. Foraging accounted for 63.2% and 68.2% of the annual energy budget in males and females, respectively. The total annual energy expenditure was 6.01 x l0^9 MJ/year, and 59% of this was accounted for by males. The gross energy requirement was 7.89 x l0^9 MJ/year. The production efficiency was 8.2% Average daily gross energy intake during potential foraging periods was 77.3 and 43.2 MJ/day for males and females, respectively. This suggested a capture rate of 0.26 and 0.15 kg of fish or muscular squid per dive for males and females, respectively. Biomass of food consumed depended on assumptions about diet composition. If southern elephant seals at South Georgia fed exclusively on squid, the consumption biomass was 2.28 x 10^6 tonnes/year.
Boyd, I. L., T. R. Walker and J. Poncet (1996). Status of southern elephant seals at South Georgia. Antarctic Science 8(3): 237-244.
Approximately 54% of the world population of southern elephant seals (Mirounga leonina) breeds at South Georgia. A partial survey in 1951 and a complete survey in 1985, together with counts at specific sites between these times, suggested that the population (around 100 000 breeding females) had not changed significantly in 34 years. This was in contrast to marked declines in most other populations. To examine this further, we conducted a third survey in 1995. This produced an estimate of 113 444 (s e = 4902) breeding females. Taking into account improved information about the behaviour of female elephant seals since the survey in 1985, there was no significant change in the number of breeding female elephant seals between 1985 and 1995. When combined with information from the 1951 survey, this supports the view that the total population size has not changed significantly during the past 45 years. Evidence for regulation of the population by environmental factors is equivocal. We hypothesize that the lack of any net change in population size may be linked to a limited availability of high quality breeding habitat.
Bradshaw, C. J. A., C. R. McMahon , M. A. Hindell, P. A. Pistorius and M. N. Bester (2002). Do southern elephant seals show density dependence in fecundity? Polar Biology 25: 650-655.
Here we provide an alternative interpretation to that of Pistorius et al. (2001), concerningdensitydependent increases in fecundity resultingin population regulation of the southern elephant seal population at Marion Island. We do not contradict the .ndings of Pistorius et al. (2001), because it does appear: (1) that a change in fecundity has been observed, and (2) that some factor related to food supply is the most likely cause for an observed population decline and increase in reproductive performance. The main observation leadingto the interpretation of density-dependent feedback in the population of southern elephant seals at Marion Island (one of the Prince Edward Islands) is that there has been a reduction in the population’s rate of decline in recent years (reported by Pistorius et al. (1999b)), and that this could have resulted from a per capita increase in food availability. However, because rates of population change are rarely linearly constant, changes in population size should be expressed on a logarithmic, rather than a linear scale, as used by Pistorius et al. (1999b). Re-plottingthe linear values of Pistorius et al. (1999b) on the natural logarithmic scale gave no clear change in the rate of population decline; therefore, we conclude that the rate of population change (decline) has remained constant from 1986 to 1997 (r=–0.0439). The Marion Island population is part of the larger Kerguelen population, and there might be considerable overlap in the foraging areas, and possibly prey, exploited by elephant seals from all sub-populations within this larger population. Changes in the number of intra-speci.c resource competitors at Marion Island are therefore unlikely to alter per capita food availability since the Marion population constitutes approximately 1% of the total Kerguelen population. We propose an alternative hypothesis that the present data support a mechanism drivingthe proposed increase in per capita food supply through changes in either: (1) inter-speci.c food competition, (2) rates of predation, (3) changes in weather pattern or (4) disease.
Bradshaw, C. J., M. A. Hindell, N. J. Best, K. L. Phillips, G. Wilson and P. D. Nichols (2003). You are what you eat: describing the foraging ecology of southern elephant seals (Mirounga leonina) using blubber fatty acids. Proc R Soc Lond B Biol Sci 270(1521): 1283-92.
Understanding the trophodynamics of marine ecosystems requires data on the temporal and spatial variation in predator diet but, particularly for wide-ranging species, these data are often unavailable. The southern elephant seal (Mirounga leonina) consumes large quantities of fish and squid prey in the Southern Ocean relative to other marine mammals; however, how diet varies relative to seasonal and spatial foraging behaviour is unknown. We used fatty acid (FA) signature analysis of 63 blubber cores from adult female M. leonina over three seasons (winter 1999, summer 2000 and winter 2001) to determine diet structure. We detected significant differences between seasons and between the main foraging regions (Antarctic continental shelf versus pelagic). We used the FA profiles from 53 fish, squid and krill species to construct a discriminant function that would classify each seal, from its blubber sample as having a fish- or squid-FA profile. We determined that a higher proportion of M. leonina had fish-dominated diets during the winter and when foraging around the Antarctic continental shelf, and the majority had more squid-dominated diets during the summer when foraging pelagically. Thus, we were able to measure the coarse-scale diet structure of a major marine predator using FA profiles, and estimate its associated seasonal and temporal variation.
Braschi, C. (2004). Comportamento agonistico negli elefanti marini del sud. Department of Animal Biology. Roma, Italy, University of Roma "La Sapienza".
Brenner, D., S. D. Shaw, J. A. Gerber, R. F. Nachreiner and T. H. Herdt (1998). Thyroid hormone levels in stranded pacific harbor seal (Phoca vitulina) and northern elephant seal (Mirounga angustirostris) pups. World Marine Mammal Science Conference Monaco, Lawrence, KS, Society For Marine Mammalogy.
Thyroid hormones play an important role in mammalian growth and development. In this study, thyroxine (T4), truodothyronine (T3) and their free fractions (fT4 and fT3) were measured in serum of 21 northern elephant seal (Mirounga angustirostris) and 20 harbor seal (Phoca vitulina) pups housed at a rehabilitation facility on the California coast. Thyroid hormone levels were significantly higher in the harbor seal pups, probably reflecting developmental differences in their ages (neonates) compared with theelephant seal pups (weanlings). Compared with previously reported values for weanling elephant seals, mean serum T4 levels were much lower in these pups (1.4 versus 4 microg/dl). Looking at other species, harp seal pups of the same age have three times higher T4 levels than those of the elephant seal pups. These differences may be species related, or may be due to the post weaning molt, illness, anorexia, or handling stress in rehabilitated elephant seal pups. Thyroid hormone levels have not been previously reported in rehabilitated neonatal harbor seals. Compared with nursing grey and harp seal pups, the harbor seal pups' mean T4 and T3 levels (2.1 microg/dl and 71.6 nanog/dl, respectively) were relatively low. This may reflect species differences or conditions (such as chronic infection, wasting, or pollutant-induced stress) that might affect the thyroid directly or alter the levels or binding capacity of carrier proteins.
Bried, J. and D. Haubreux (2000). An aberrantly pigmented southern elephant seal (Mirounga leonina) at Iles Kerguelen, southern Indian Ocean. Marine Mammal Science 16(3): 681-684.
Aberrant pelage colors are known to exist in pinnipeds. Albinism has been reported for the Steller's sea lion (Eumetopias jubatus), northern fur seal (Callorhinus ursinus) (Scheffer 1962 in King 1983), and subantarctic fur seal (Arctocephalus tropicalis). Piebald and red-eyed pale brown northern fur seals have been observed (Bonner 1968), as well as non-albino white and "golden" Antarctic fur seals (A. gazella) (Bonner 1968, 1981; see also photographs in Gentry and Kooyman 1986 and Reeves et al. 1992). However, these reports are only of otariids. Our observation took place at Iles Kerguelen (48 degree 28'-50 degree S, 68 degree 37'-70 degree 35'E) on 14 October 1993, while we were performing an annual census of the population of southern elephant seals (Mirounga leonina) of the Peninsule Courbet, in the eastern part of the main island.
Briggs, K. T. and G. V. Morejohn (1975). Sexual dimorphism in the mandibles and canine teeth of the Northern elephant seal. Journal of Mammalogy 56(1): 224-231.
Briggs, G. D., R. V. Henrickson and B. J. Le Boeuf (1975). Ketamine immobilization of northern elephant seals. J. Am. Vet. Med. Assoc. 167(7): 546-548.
Ketamine was used as an immobilizing agent to obtain biological specimens from northern elephant seals in their natural habitat. Effective immobilization was achieved with dosages of 1.4 to 6.9 mg/kg of body weight.
Briggs, K. T. and G. V. Morejohn (1976). Dentition, cranial morphology and evolution in elephant seals. Mammalia 40: 199-222.
Brown, R. F. (1997). Pinnipeds in Oregon: status of populations and conflicts with fisheries, fish resources and human activities. Stone, Gregory; Goebel: status, trends and issues A symposium of the 127th Annual Meeting of the American Fisheries Society, August 28, 1997, Monterey, California Monterey Bay Aquarium & New England Aquarium, Monterey & Boston 1997 i-vii, 1-179 Chapter pagination 124-134.
Brown, D. J., I. L. Boyd, G. C. Cripps and P. J. Butler (1999). Fatty acid signature analysis from the milk of Antarctic fur seals and southern elephant seals from South Georgia: implications for diet determination. Marine Ecology Progress Series 187: 251-263.
Brownell, R. L. and D. G. Ainley (1976). Southern elephant seals in the Ross Sea. Antarctic Journal of the United States 11(3): 189-190.
Observations are briefly reported on one subadult male elephant seal sighted at Cape Crozier on Dec. 18-21, 1974 and Jan. 18-27, 1975, and two adult males near Scott Base on or about Feb. 10, 1975. None of the animals had begun their molt. The elephant seal breeding locality nearest Ross I. is Macquarie I., approx 2,400 km to the northwest, where mature males begin their molt in late Jan. or Feb.
Brownell, R. L., Jr., B. E. Curry, W. Van Bonn and S. H. Ridgway (2000). Conservation conundrum. Science 288(5475): 2319-2320.
Bryden, M. M. (1966). Control of growth in two population of elephant seals. Nature 217: 1106-1108.
Bryden, M. M. (1968 a). Growth and function of the subcutaneous fat on the elephant seal. Nature 220: 591-599.
Bryden, M. M. (1968 b). Lactation and suckling in relation to early growth of the Southern elephant seal, Mirounga leonina L. Australian Journal of Zoology 16: 739-748.
Bryden, M. M. and G. H. K. Lim (1969). Blood parameters of the southern elephant seal (Mirounga leonina, Linn.) in relation to diving. Comparative biochemistry and physiology 28(1): 139-148.
Certain properties of the blood of southern elephant seals were studied at Macquarie I. in order to determine alterations which may be associated with the ability of this species to remain submerged for long periods. Blood volume increased from 11 percent body weight in newborn seal pups to 15 percent in adults. Hemoglobin concentration was the same as that of man, despite a lower red cell count, due to a greater mean corpuscular volume in the seal. Hematocrit was about 50 in newborn seals and 65 in adults. Changes in blood volume, red cell count, and hematocrit occurred as the young seal went to sea.
Bryden, M. M. (1969 a). Relative growth of the major body components of the Southern elephant seal, Mirounga leonina (L.). Australian Journal of Zoology 17: 153-177.
Bryden, M. M. (1969 b). Growth of the southern elephant seal, Mirounga leonina (Linn.). Growth 33: 69-82.
Bryden, M. M. (1971). Size and growth of viscera in the Southern elephant seal, Mirounga leonina (L.). Australian Journal of Zoology 19: 103-120.
Bryden, M. M. (1972). Body size and composition of elephant seal (Mirounga leonina): absolute measurements and estimate from bone dimensions. Journal of Zoology London 167: 265-276.
Bryden, M. M. (1973). Growth patterns of individual muscles of the elephant seal, Mirounga leonina (L.). Journal of Anatomy 116(1): 121-133.
Growth patterns of muscles are presented, based on weights of 73 muscles from each of 44 male and 43 female elephant seals. Most data represent individual muscle growth patterns, but a few muscles which were closely related morphologically and functionally were combined. No differences in relative growth rate between growth phases were demonstrated for 41 muscles. Of the remaining 32 muscles, 24 had an increased growth rate during the aquatic phase of the young seal's life, while the growth rate of 8 muscles decreased relative to the terrestrial phases. It appears that the foreflippers are more important in the aquatic environment than has been suspected. Significant sexual differences in muscle growth were demonstrated for only three muscles.
Bryden, M. M. and W. J. L. Felts (1974). Quantitative anatomical observations on the skeletal and muscular systems of four species of Antarctic seal. J. Anatomy 118(3): 589-600.
In order to gather data relevant to musculoskeletal function in Antarctic seals, individual bones and muscles of mature specimens of Ross Ommatophoca rossi, leopard Hydrurga leptonyx, crabeater Lobodon carcinophagus and elephant Mirounga leonina seals were dissected fresh and weighed. Bones and muscles were grouped according to anatomical location, and groups and individual components were compared between species, using relative weight as a measure of size. On the basis of weight, the skull, the muscles of the head and the muscles supporting the head of the leopard seal were all very large. Muscles associated with grasping and swallowing food were very large in the Ross seal. Muscles of the head and muscles supporting the head of the crabeater seal were small, although the skull was large. Bones and intrinsic muscles of the thoracic limb of the leopard seal were large, but muscles supporting the thoracic limb were large in the crabeater and elephant seals. The thoracic limb of the Ross seal was relatively poorly developed. The musculoskeletal system of the caudal lumbar region and pelvic limb was particularly well developed in the crabeater seal, and relatively poorly developed in the elephant seal. It is possible to interpret many of these observations in terms of differing functions of different parts of the musculoskeletal system in the various species, especially in relation to locomotion and body movements in an aquatic environment.
Bryden, M. M. (1988). Southern elephant seals as subjects for physiological research. Proceedings of the Royal Society of Tasmania 122(1): 153-157.
Anatomical and physiological studies of southern elephant seals (Mirounga leonina), particularly in the post-natal period, raise questions of relative musculature growth, control of metabolism, circulation and temperature regulation, which could be important in the understanding of these processes in mammals and of their contribution to adaptation to environmental extremes.
Bryden, M. M., P. Buckendahl, J. Sanders, C. L. Ortiz and D. J. Kennaway (1994). Plasma melatonin concentration in neonatal northern elephant seals, Mirounga angustirostris. Comparative Biochemistry and Physiology A 109(4): 895-904.
The development of pineal function in northern elephant seals was examined in an attempt to understand the physiological basis for previously observed high daytime levels of melatonin in neonatal southern elephant seals. Pineal glands from four northern elephant seal pups, estimated age less than 1 week, weighed 3.0 plus or minus 0.80 g, which was significantly less than that previously found in southern elephant seals (4.6 plus or minus 0.35 g). Midday concentrations of plasma melatonin in pups averaged more than 3000 pmol/l in the first 5 days post-partum, but declined rapidly to less than 400 pmol/l after day 9. Daytime melatonin levels in northern elephant seals tended to be lower than in southern elephant seals, although they were very high compared with other species. A circadian cycle of plasma melatonin concentration was observed in newborn northern elephant seals, with levels of 3000-5000 pmol/l during the day, rising to more than 10,000 pmol/l late in the dark phase. Soon after weaning at 4 weeks of age, daytime and night-time levels were in the range 60-100 pmol/l and 100-400 pmol/l, respectively. When approximately 10 weeks old, most samples were in the range 100-400 pmol/l with no discernible difference between day and night levels. The results do not support the hypothesis that the pineal gland is involved in thermogenesis in new-born southern elephant seals. Instead, the very active pineal gland may contribute to energy conservation, by lowering body temperature, particularly at night. As physical insulation is acquired by the deposition of blubber, the mechanism is not required and melatonin falls to adult levels.
Bryden, M. M. (1999). Stones in the stomachs of southern elephant seals. Marine Mammal Science 15(4): 1370-1373.
In a study of southern elephant seals carried out at Macquarie Island in the 1960s (Bryden 1968, 1969, 1971), I recorded but did not publish the weight of sand and stones in the stomachs of 88 animals, ranging in age from birth to 16 yr. The methods of data collection were described in Bryden (1971). Forty animals were more than six months old and had fed at sea. The stomachs contained a mean of 2.4 kg of sand and stones in this group (range 0.0-8.6 kg). The stomachs of three animals contained no sand and stones but did contain food items (whole squid). That observation, and the fact that the seals were very fat, suggested that they had just come ashore. Subjective judgment suggested that those animals believed to have been ashore for several days or weeks had more sand and stones in their stomachs than those judged to have just arrived.
Bryden, M. M., S. O'Connor and R. Jones (1999). Archaeological evidence for the extinction of a breeding population of elephant seals in Tasmania in prehistoric times. International Journal of Osteoarchaeology 9(6): 430-437.
Southern elephant seals, Mirounga leonina L., do not inhabit the northwest coast of Tasmania today, but archaeological evidence indicates that they did so in prehistoric times, when they constituted an important food resource to the Aboriginal tribes of the region. Skeletal remains of at least 300 elephant seals were present in one midden alone. There is distinct sexual dimorphism in the canine teeth of elephant seals, and regular seasonal variations in the density of concentric layers of calcified dentine, as well as the pattern of these variations, provide insight into the age and reproductive history of individual animals. The sectioned canine teeth of 145 southern elephant seals (107 females, 38 males) from a Tasmanian midden were examined to provide information on the age and sex of the seals as well as aspects of their reproductive history. The age distributions differed between the sexes, and partly explain the different frequencies of males and females. All the males were young, immature individuals, none more than 6 years old, which is about the age at which a secondary growth spurt occurs in males and results in a marked sexual disparity in body size. By contrast, 47% of the females were of breeding age, 26% had given birth to pups, and several were up to 20 years of age. At least 26% of animals were estimated to be less than 3 months old, the approximate age at which they go to sea for the first time, confirming that they were born on the northwest Tasmanian coast. Animals were killed throughout the year, and there is evidence of change in reproductive pattern over time, consistent with a response to predation pressure. The evidence points to the conclusion that the population was exterminated by Aboriginal hunters, through selective exploitation of smaller animals, which included significant numbers of breeding females.
Burgess, W. C., P. L. Tyack, P. J. Le Bieuf and D. P. Costa (1998). A programmable acoustic recording tag and first results from free-ranging northern elephant seals. World Marine Mammal Science Conference Monaco, Lawrence, KS, Society For Marine Mammalogy.
A new recoverable acoustic recording tag developed by the authors has measured diving pattern. ambient temperature, noise exposure and respiratory and cardiac sounds on free-ranging northern elephant seals (Mirounga angustirostris). The Compact Acoustic Probe (CAP) comprises a hydrophone, thermistor and pressure transducer in a 36 cm long. 10 cm diameter cylindrical hydrodynamic pressure housing capable of -withstanding 2000 m depth. The enclosed logging electronics include a “TattleTale 7” data acquisition engine and a 340 Mb hard disk together with a custom low-power operating system capable of multi-channel interrupt-driven sampling at 5 kHz. The complete tag weighs 3.0 kg in air, or 0.9 kg in water. Initial deployments of the CAP on five juvenile elephant seals, translocated from and returning to Ano Nuevo, California, measured ambient and vessel noise exposure, oceanographic ranging (RAFOS) and thermometry (ATOC) beacons and acoustic signatures of velocity, swim stroke, surface respiration, cardiac function and possible vocalizations. The results suggest promising future applications of CAP technology to investigate the physiology, behavior and noise response of free-ranging marine mammals.
Burgess, W. C., P. L. Tyack, B. J. Le Boeuf and D. P. Costa (1998). A programmable acoustic recording tag and first results from free-ranging northern elephant seals. Deep-Sea Research Part II Topical Studies in Oceanography 45(7): 1327-1351.
A hydrophone-equipped tag recorded exposure to noise, as well as physiological and behavioral sounds, on free-ranging northern elephant seals (Mirounga angustirostris). The compact acoustic probe (CAP) consisted of the hydrophone, a thermistor, and a pressure transducer in a 36 cm long, 10 cm diameter cylindrical hydrodynamic housing capable of withstanding 2000 m depth. The enclosed logging electronics included a programmable "Tattle Tale 7" data acquisition engine and a 340 Mb hard disk. A custom low-power operating system supported multi-channel interrupt-driven sampling at 5 kHz. The complete tag weighed 0.9 kg in water and displaced 2.11. During five deployments on juveniles translocated from and returning to Ano Nuevo, California, CAP tags measured dive pattern, ambient and vessel noise exposure, oceanographic ranging (RAFOS) and thermometry (ATOC) beacons, acoustic signatures of swim stroke, surface respiration, and cardiac function, and possible vocalizations.
Burnham, K. P. and D. R. Anderson (2001). Kullback-Leibler information as a basis for strong inference in ecological studies. Wildlife Research 28(2): 111-119.
We describe an information-theoretic paradigm for analysis of ecological data, based on Kullback-Leibler information, that is an extension of likelihood theory and avoids the pitfalls of null hypothesis testing. Information-theoretic approaches emphasise a deliberate focus on the a priori science in developing a set of multiple working hypotheses or models. Simple methods then allow these hypotheses (models) to be ranked from best to worst and scaled to reflect a strength of evidence using the likelihood of each model (gi), given the data and the models in the set (i.e. L(gi[vertical bar]data)). In addition, a variance component due to model-selection uncertainty is included in estimates of precision. There are many cases where formal inference can be based on all the models in the a priori set and this multi-model inference represents a powerful, new approach to valid inference. Finally, we strongly recommend inferences based on a priori considerations be carefully separated from those resulting from some form of data dredging. An example is given for questions related to age- and sex-dependent rates of tag loss in elephant seals (Mirounga leonina).
Burton, H. R. (1985). Tagging studies of male southern elephant seals (Mirounga leonina L.) in the Vestfold Hills area, Antarctica, and some aspects of their behaviour. Studies of sea mammals in South Latitudes. J. K. L. M. M. Bryden. Northfield, South Austr. Museum: 19-30.
Resightings of tagged seals suggest migration between Antarctica and subantarctic islands. The summer minimum of immature seals on the mainland beaches of the Vestfold Hills occurred about a month earlier (mid-Jan.) than on Macquarie I. and Heard I. Very young seals (<2 m in length) appeared and moulted on the mainland beaches when sea ice broke out early and allowed them access; it is suggested that sea ice break-out is a necessary but not a sufficient factor determining the arrival time of the first seals for the autumn-winter haul-out. During cyclonic weather conditions (wind speed >75 km/h (40 knots), daily wind run >650 km), seals already hauled out on Davis Beach departed in significant numbers. (Auth. mod.)
Burton, H. (1986). A substantial decline in numbers of the southern elephant seal at Heard Island. Tasmanian Naturalist 86: 4-8.
Burton, H. R. (1991). Southern elephant seal foraging in the southern ocean. Kingston, Tasmania, Australian Antarctic Research Program.
A project is proposed to determine the foraging areas of southern elephant seals from Heard I. by using time-depth- position recorders and satellite transmitters; to examine the diving performance of southern elephant seals from Heard I. and to compare this with data already obtained from seals at Macquarie I., using attached time-depth-position recorders; to census the southern elephant seal population on Heard I. during the pupping season (Oct.) to determine the trend in population size; to tag and to search for tags on southern elephant seals at Heard I. to obtain data on migration between Heard I. and other localities; to weigh over 300 pups of each sex at birth and at weaning to determine the maternal investment at Heard I.; to determine, by stomach lavaging, the diet of young animals (up to two years old) that haul out on Heard I. throughout the year and of adults that have been anaesthetized for retrieval of time- depth recorders. This will lead to a better understanding of the feeding ecology of elephant seals.
Burton, H. R., T. Arnbom, I. L. Boyd, M. N. Bester, D. Vergani and I. Wilkinson (1997). Significant differences in weaning mass of southern elephant seals from five sub-Antarctic islands in relation to population declines. Antarctic communities: species, structure and survival. B. Battaglia, J. Valencia and D. W. H. Walton. Cambridge, U.K., Cambridge Un. Press: 335-338.
The mass of southern elephant seal pups (n=3292) was measured at weaning and compared across the major populations. Weaning mass was found to vary significantly between locations. Weaning mass was greatest in the Atlantic sector of the southern ocean where populations have been stable and it was smallest in the Pacific and Indian Ocean sectors where populations have been in decline. The weaning masses at Marion and Heard islands, where populations are continuing to decline rapidly (4-5% per annum), were significantly less than at Macquarie I., where populations have declined less (<1% per annum) in recent years. Female elephant seals at Marion I. deliver up to 30% less energy to their pups during lactation than females at King George I.
Burton, R. K. and P. L. Koch (1999). Isotopic tracking of foraging and long-distance migration in northeastern Pacific pinnipeds. Oecologia 119(4): 578-585.
We investigated the impact of foraging location (nearshore vs offshore) and foraging latitude (high vs middle) on the carbon (<delta>13C) and nitrogen (<delta>15N) isotope compositions of bone collagen of northern fur seals (Callorhinus ursinus), harbor seals (Phoca vitulina), California sea lions (Zalophus californianus), and northern elephant seals (Mirounga angustirostris). Nearshore-foraging harbor seals from California had <delta>13C values 2.0‰ higher than female northern elephant seals foraging offshore at similar latitudes. Likewise, nearshore-foraging harbor seals from Alaska had values 1.7‰ higher than male northern fur seals, which forage offshore at high latitudes. Middle-latitude pinnipeds foraging in either the nearshore or offshore were 13C enriched by \sim1.0‰ over similar populations from high latitudes. Male northern elephant seals migrate between middle and high latitudes, but they had <delta>13C values similar to high-latitude, nearshore foragers. Female northern fur seal <delta>13C values were intermediate between those of high- and middle-latitude offshore foragers, reflecting their migration between high- and middle-latitude waters. The <delta>13C values of California sea lions were intermediate between nearshore- and offshore-foraging pinnipeds at middle latitudes, yet there was no observational support for the suggestion that they use offshore food webs. We suggest that their "intermediate" values reflect migration between highly productive and less-productive, nearshore ecosystems on the Pacific coasts of California and Mexico. The relative uniformity among all of these pinnipeds in <delta>15N values, which are strongly sensitive to trophic level, reveals that the carbon isotope patterns result from differences in the <delta>13C of organic carbon at the base of the food web, rather than differences in trophic structure, among these regions. Finally, the magnitude and direction of the observed nearshore-offshore and high-to middle-latitude differences in <delta>13C values suggest that these gradients may chiefly reflect differences in rates and magnitudes of phytoplankton production as well as the <delta>13C value of inorganic carbon available for photosynthesis, rather than the input of 13C-enriched macroalgal carbon to nearshore food webs.
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Campagna, C., B. J. Le Boeuf, M. Lewis and C. Bisioli (1992). Equal investment in male and female offspring in southern elephant seals. Journal of Zoology London 226: 551-561.
Sex ratio theory predictions concerning differential parental investment in offspring by sex were tested on southern elephant seals, Mirounga leonina , breeding at Peninsula Valdes, Argentina. Females invested equally in sons and daughters, as reflected by the similar mass at birth (mean plus or minus 1 S.D.) of 14 males (44 multiplied by 1 plus or minus 6 multiplied by 5 kg) and 14 females (43 multiplied by 4 plus or minus 3 multiplied by 8 kg), and similar mass at weaning of 52 males (131 multiplied by 5 plus or minus 22 multiplied by 4 kg) and 38 females (131 multiplied by 4 plus or minus 18 multiplied by 3 kg). There were also no sex differences in the rate of mass gain during nursing (males = 4 multiplied by 0 plus or minus 0 multiplied by 9 kg/day; females = 3 multiplied by 9 plus or minus 0 multiplied by 8 kg/day), rate of mass loss during the first month of post-weaning fast (males = 0 multiplied by 85 plus or minus 0 multiplied by 19 kg/day; females = 0 multiplied by 92 plus or minus 0 multiplied by 15 kg/day), mean age at weaning (males = 22 multiplied by 3 plus or minus 1 multiplied by 6 days; females = 22 multiplied by 7 plus or minus 1 multiplied by 7 days), and female nursing behaviour. Mother's size accounted for most of the variation in mass of pups at weaning. Mothers ranked as small, medium and large, weaned pups with a mean mass of 102, 130 and 145 kg, respectively. The sex ratio of weanlings did not differ from unity. These data are consistent with Fisher's (1930) sex ratio theory.
Campagna, C. and M. Lewis (1992). Growth and distribution of a southern elephant seal colony. Marine Mammal Science 8(4): 387-396.
In contrast with most southern elephant seal, Mirounga leonina , colonies, births at Peninsula Valdes, Argentina, increased from 7,455 in 1982 to 9636 in 1990. Colony size during the 1990 breeding season, including pups, was estimated at 19,000. Colony growth may respond to abundant food resources and lack of competitors. The range of distribution of elephant seals in Patagonia has not changed since at least 1972 but the spatial distribution of births along the coastline of Peninsula Valdes has varied. In 1982, 58% of the births occurred in the northeast portion of the Peninsula versus 36% in 1990. Females may prefer to give birth on broad, sandy beadhes. In 1982, 56% of the females gave birth on pebble beaches and 44% on sandy beaches. In 1990, 24% bred on pebbles versus 76% on sand. Sand substrate may be preferred by females because it may confer thermoregulatory advantages in relieving heat stress.
Campagna, C., M. Lewis and R. Baldi (1993). Breeding biology of southern elephant seals in Patagonia. Marine Mammal Science 9(1): 34-47.
Elephant seals breed in Patagonia (Peninsula Valdes, Argentina) from late August to early November, reaching peak numbers during the first week in October. Observations of this population over the past ten years yielded similar results. Eighty percent of the pups were born by 2 October. Most (96%) of 663 females marked during three breeding seasons gave birth to a pup. Females stayed on land a mean of 28 d, gave birth 6 d after arrival, nursed their pups for 22 d, and copulated a mean of 2.5 times 20 d after parturition and 2 d before departure. Copulations peaked during the third week in October. Males spent 57-80 d on land fasting and defending harems of up to 134 females (median 11-13 females, depending on year). Most (96%) marked females that gave birth (n = 626) also weaned their pups successfully. Pup sex ratio was unity. Harems were smaller and breeding occurred about three weeks earlier in Patagonia than in other colonies. Thermal conditions, day length and food availability may explain clines in the timing of breeding events between populations. Other parameters of the breeding season for the expanding Patagonia colony are similar to those for declining southern elephant seal populations elsewhere.
Campagna, C. (1994). Patagonian prospects. Wildlife Conservation 97(2): 44-48.
Campagna, C., B. J. Le Boeuf, S. B. Blackwell, D. E. Crocker and F. Quintana (1995). Diving behaviour and foraging location of female southern elephant seals from Patagonia. Journal of Zoology London 236(1): 55-71.
Our aim was to describe the free-ranging diving pattern and to determine the location of foraging of pregnant female southern elephant seals, Mirounga leonina, from Peninsula Valdes, Argentina. This colony is unusual in two respects: it is removed from deep water by a broad shallow shelf (345-630 km wide), and colony numbers have been increasing in recent years in contrast to numbers from other southern hemisphere colonies that are stable or in decline. Microprocessor controlled, geolocation-time-depth recorders were deployed on four females, recording a total of 15,836 dives (270 dive days) during the period February to April, 1992. Departing seals crossed the continental shelf quickly and did not show signs of foraging until reaching deep water, due east of the colony in the South Atlantic Ocean. Diving was virtually continuous (93% of the time underwater) with overall mean ( plus or minus S.D.) rates of 2.5 plus or minus 0.2 dives/h, mean dive durations of 22.8 plus or minus 7.1 min with 1.6 plus or minus 0.6 min surface intervals between dives, and dive depths of 431 plus or minus 193 m. The diving pattern of females from Patagonia is similar to that of seals from colonies where numbers are decreasing (Macquarie stock) or are stable (South Georgia Island). Our subjects did not, however, feed in or south of the Antarctic Polar Front, or in cold waters along the Antarctic coast, where seals from declining or stable colonies forage.
Campagna, C., M. Lewis and F. Quintana (1996). Population trends and distribution of Southern elephant seals on Peninsula Valdes. Pto. Madryn, Chubut (Argentina), Fundacion Patagonia Natural: 23.
Southern elephant seals, Mirounga leonina, breed and molt on Peninsula Valdes, Argentina. To estimate the number and distribution of seals in the area, four aerial (1982, 1989, 1990 and 1992) and one terrestrial survey (1995) were conducted at the peak of the breeding season (first week of October). During aerial surveys, all harems were photographed and solitary individuals by sex and age categories were recorded. Females were counted from photopraphs and pup production was estimated based on the number of females ashore plus weanlings. During terrestrial surveys, all individuals were categorized by sex and age. Contrasting with most Southern elephant seal colonies, births at Peninsula Valdes increased 41%, from 7,455 in 1982 to 11,647 in 1995. At the peak of the breeding season of 1995 there were a total of 24,147 animals ashore, including pups. There were 477 harems in 1982 and 511 in 1995. Maximum harem size was 69 females in 1982 and 131 in 1995. The range of distribution of elephant seals in Patagonia did not change during the study period, but the spatial distribution of births along the coastline of Peninsula Valdes varied with the increase in numbers. In 1982, 58% of births occurred in 106 km in the NE portion of the peninusla, versus 36% in 1990 and 28% in 1995 for the same area. In 1995, 71% of the females gave birth in 77 km along the SE coast. The number and distribution of adult females during the molt was estimated in two aerial surveys conducted the last weeks of December 1993 and January 1994. Counts yielded 1,200 and 6,600 animals, respectively. The distribution of females during the molt was similar to the breeding season. Abundant food resources may be a determinant factor for population growth.
Campagna, C. (1998). Foraging ecology of the expanding patagonian populations of southern elephant seals and sea lions. World Marine Mammal Science Conference Monaco, Lawrence, KS, Society for Marine Mammalogy.
Patagonian populations of the southern elephant seal (SES), Mirounga leonina and the South American sea lion (SSL), Otaria flavescens, top predators in the South Western Atlantic ecosystem, are expanding, an exception among stable or declining populations of these species elsewhere. An understanding of their foraging ecology may provide comparative data relevant to the declining populations of SES (Kerguelen and Macquarie) and SSL (Falkland Islands). Time-depth recorders or satellite transmitters were deployed to describe the diving behavior and the location at sea of 28 adult SES (21 females; 7 males) during the post-breeding (PB) and post-molt (PM) pelagic trips and for 22 adult female SSL during the breeding season. Studies were conducted at Peninsula Valdés (42' S), located at the edge of the shallow (< 100 m) and wide (300-400 km) Patagonian shelf a reliable, highly productive and accessible foraging ground. Male and female SES behaved at sea as individuals from declining or stable colonies. Females crossed the shelf in 3-7 days, spending 89 % of the recorded time in deep water beyond the shelf Patagonian seals, however, did not forage near the Antarctic Polar Front, as apparently do those from declining or stable rookeries. PB and PM females fed in temperate waters of the SW Atlantic, between 36 and 50 S and up to 2,281 km from shore. Males have localized foraging areas near the shell' margin or slope, where wandering albatrosses from South Georgia are also known to feed. Obliged to return to land to attend their pup, lactating female SSL forage on the shelf, traveling mean distances of 300 km per feeding excursion. Their diving behavior and foraging ranges were, however, similar to those described for individuals of the Falkland lslands, a population that has declined to very low levels. While elephant seals may be exploiting productive frontal zone environments created by the sub Antarctic Falkland Current, the foraging areas of sea lions seem tied to tidal and coastal fronts within the shelf.
Campagna, C., F. Quintana, B. J. Le Boeuf, S. Blackwell and D. E. Crocker (1998). Diving behaviour and foraging ecology of female southern elephant seals from Patagonia. Aquatic Mammals 24(1): 1-11.
We asked if non-gestating, adult female southern elephant seals, _Mirounga leonina_, from Peninsula Valdes, Argentina, forage on the wide continental shelf off the peninsula during the post-breeding trip to sea (PB females), or whether they forage in deep water, where gestating, post-moult (PM) animals have been shown to do. More than 16,600 dives were recorded with geographic-location time-depth recorders deployed in five PB females. Data were compared with about 19,500 dives from six gestating, PM animals. Four satellite transmitters linked to the Argos system were deployed in PB (2) and PM (2) animals. During both trips females displayed continuous, deep, and long-duration diving. PB females crossed the shelf in 3-7 days, spending 89% of the recorded time at sea over waters deeper than 200 m. A diel pattern in the frequency distribution of dives/hr, dive depth and dive duration was apparent in both PB and PM individuals beyond the continental shelf. Deeper and longer dives were observed during daylight hours, consistent with feeding on dielly-migrating prey. PB females concentrated their foraging effort in temperate waters of the SW Atlantic, between 36 degrees and 46 degrees S and up to 1200 km from shore. PM females travelled further, reaching approximately 50 degrees S and 2281 km east from the rookery. The longest migration was a PM trip of 11,600 km. Females from Peninsula Valdes, the only colony for the species with an increasing birth rate, do not feed near or south of the Antarctic Polar Front, where most seals from more southerly stable or decreasing rookeries forage.
Campagna, C., M. A. Fedak and B. J. McConnell (1999). Post-breeding distribution and diving behavior of adult male southern elephant seals from Patagonia. Journal of Mammalogy 80(4): 1341-1352.
Seven post-breeding adult male southern elephant seals, Mirounga leonina, were tracked using satellite-relay data loggers (SRDL) in 1994-1996. Two animals also were instrumented with a time depth recorder(TDR). Animals were monitored for 31-112 days at the end of the breeding season as they left Peninsula Valdes, Argentina. Males traveled less than or equal to 1,300 km from the breeding rookery but remained in temperate waters of the SW Atlantic Ocean, between 42 degree S and 55 degree S. The maximum travel distance recorded for the entire trip for any one seal was >4,500 km. Five males swam across the continental shelf in 3-11 days and stayed along the shelf margin or break where travel rates decreased markedly and remained low, suggesting that they may have reached foraging grounds. The other two males remained on the continental shelf during the entire time that they were tracked at sea. One of them was tracked for 66 days and concentrated his activity only 6-10 km off the coast of Patagonia in two areas located 700-800 km S of Peninsula Valdes. He never dived deeper than 94 m. The diving behavior sampled by one working TDR and several SRDL were similar. Dives over the continental shelf were mostly down to the seabed. Some dives over the shelf break were to the seabed (down to 1,500 m) but most were mid-water (300-600 m) and were deeper during the day. Previously studied post-breeding and post-molt adult females from the same colony spent virtually all their time over deep water off the shelf in the latitudinal range of 36-50 degree S. Their movements were less localized than those of males and dives did not take them to near the ocean bottom.
Campagna, C., A. L. Rivas and M. R. Marin (2000). Temperature and depth profiles recorded during dives of elephant seals reflect distinct ocean environments. Journal of Marine Systems 24(3-4): 299-312.
Foraging adult southern elephant seals, Mirounga leonina, from Peninsula Valdes, Argentina, dive continuously while travelling across the continental shelf towards deep waters of the SW Atlantic. This study attempted to identify distinct ocean environments encountered by these seals during foraging migrations based on bathymetric and water temperature profiles, and to interpret these profiles in terms of mixing and systems of currents. Depth and water temperature were obtained with data loggers carried by 14 diving adult animals during spring (October-December) and summer (February-March) months. Dive depths allowed us to unmistakably differentiate extensive areas of the SW Atlantic: the Patagonian shelf, shelf slope and open waters of the Argentine Basin. Water temperature profiles added further details to the latter general oceanographic areas, and could be related to large-scale oceanographic processes that led to different water column structures. Temperature data reflected the mixing effects of winds and tides in coastal waters, the formation of a thermocline in mid-shelf areas, the northward flow of the sub-antarctic Malvinas Current at the edge of the shelf, and the effect of the subtropical Brazil Current further east over deep off-shelf waters. Some of these distinct areas are known for their enhanced primary production associated with frontal systems. The study shows that elephant seals could be useful, low-cost platforms to obtain oceanographic data. Studies that require extensive sampling of physical variables in large areas over long periods of time would benefit from this approach, pending on more precise and frequent locations of animals at sea.
Campagna, C., J. Dignani, S. B. Blackwell and M. R. Marin (2001). Detecting bioluminescence with an irradiance time-depth recorder deployed on southern elephant seals. Marine Mammal Science 17(2): 402-414.
While at sea, elephant seals (Mirounga spp.) spend 90% of their time underwater, at mean depths of 400-500 m while foraging during both daytime and nighttime. Although most surface light is lost before reaching these depths, elephant seals have adaptations to low light levels that suggest visual predation. They have large eyes with a wide range of pupillary dilation, rapid adjustment to darkness and a retina that has a peak sensitivity shifted to the blue-green. At depths where seals spend most of their time, bioluminescence is the main source of light, and it is produced at levels and wavelengths that can be detected by the elephant seal eye. A visual predator foraging in deep waters may then be cueing on bioluminescent prey or may use stimulated bioluminescence for indirect detection of prey. We deployed irradiance-time-depth recorders (I-TDRs) on female southern elephant seals, M. leonina, from Peninsula Valdes, Argentina, in an attempt to sample the luminescent field to which elephant seals were exposed during dives. Previous work has interpreted the foraging behavior of elephant seals indirectly from depth, water temperature, swim speed, and underwater sound data. Our results indicate that diving elephant seals are exposed throughout the water column to irradiance, which most likely originates in bioluminescent organisms. This paper is an innovative approach to the understanding of diving behavior. We acknowledge that our results are limited by technical difficulties, which need to be overcome to examine the link between bioluminescence and seal foraging behavior. This work is a step towards that goal.
Campbell, R. R. (1987). Status of the northern elephant seal, Mirounga angustirostris, in Canada. Can. Field Nat. 101( 2): 266- 270.
The northern elephant seal, Mirounga angustirostis , inhabits the Pacific coast of North America, with breeding colonies occurring historically from the Point Reyes Peninsula, north of San Francisco to Cabo San Lazaro and Magdalena Bay, Baja California, Mexico. Feeding areas ranged from the tip of the Baja Peninsula to British Columbia and southeast Alaska. These seals were virtually exterminated through commercial sealing by 1860. Elephant Seals under the protection of Mexican law and later U.S. regulation have made a remarkable recovery and now reoccupy almost all of their historic breeding range, and are so common as to be no longer considered rare or endangered.
Carlini, A. R., M. E. I. Marquez, G. Soave, D. F. Vergani and P. A. Ronayne de Ferrer (1994). Southern elephant seal, Mirounga leonina: composition of milk during lactation. Polar Biology 14(1): 37-42.
Carlini, A. R., G. A. Daneri, M. E. I. Marquez, G. E. Soave and S. Poljak (1997). Mass transfer from mothers to pups and mass recovery by mothers during the post-breeding foraging period in southern elephant seals (Mirounga leonina) at King George Island. Polar Biology 18(5): 305-310.
Mass transfer from mother to pup during the lactation period, and mass recovery for the same females during the foraging period were measured in the southern elephant seal at King George Island, Antarctica. During the 19.2 +/- 0.9-day lactation period measured (which represented 87% of the entire nursing), females lost a mean mass of 10.56 +/- 1.76 kg/day (n = 27), while their pups gained a mean mass of 5.27 +/- 1.1 kg/day. There was a correlation between daily body weight gain in pups and daily weight loss by their mothers. Pup weaning mass was positively related to maternal post-partum mass. Serial samples showed that weight losses by females and gains by their pups were not linear over lactation, but showed lower values at the beginning and at the end of lactation. During the 60.5 +/- 6.2-day foraging phase between the end of lactation and molt, females gained 2.21 +/- 0.65 kg/day (n = 12), or 54% of the mass lost during nursing. Growth rates reported here are higher than those reported in other-breeding sites. However, the ratio of body mass loss by females to gain by their pups was similar, suggesting that higher growth rates and greater weaning mass at South Shetland are due to a higher mean weight of females on arrival at this breeding site. The foraging period was shorter and the mass gained greater than those measured at South Georgia; this could be related to relatively shorter distances to foraging areas.
Carlini, A. R. (1998). Energy investment in pups of southern elephant seals and mass changes in females while at sea at King George Island.
Carlini, A. R., M. E. I. Marquez, G. A. Daneri and S. Poljak (1999). Mass changes during their annual cycle in females of southern elephant seals at King George Island. Polar Biology 21(4): 234-239.
Mass changes in female southern elephant seals, sampled sequentially at different points through their annual cycle, were measured at King George Island, South Shetland Islands, during the 1995/1996 and 1996/1997 field seasons. Females weighed after they had given birth showed an increase of 37 ± 36 kg (mean ± SD), which represented 6.2 ± 6.4% in relation to their mass in the first breeding season. During the first aquatic phase, between the end of lactation and the beginning of moult, females gained a mean of 128 ± 35 kg, (n = 18) (2.19 ± 0.65 kg day-1), which represented between 27 and 83% of the mass they had lost during lactation. Nine females followed during moulting showed a mass loss rate of 5.0 ± 0.4 kg day-1, which was half the rate during lactation. Total mass loss during moulting (129 ± 22 kg) was not significantly different from mass gain for the same females between lactation and moult (135 ± 37 kg). Furthermore, at the end of moulting, female mass was not significantly different from the mass at the end of lactation. These masses represented 65 ± 5% and 64 ± 5%, respectively, of their initial mass after parturition. During the second period at sea, from the end of the moult until females hauled out to give birth in the following breeding season, the estimated mass gain was 1.45 ± 0.24 kg day-1 (n = 5), which was not significantly different to the rate of mass gain shown by the same females during the first period at sea (2.26 ± 0.70 kg day-1). Total mass gain during the second aquatic phase (364 ± 63 kg) was not correlated with the mass at the end of moulting, but it was positively related to the mass loss experienced by females from parturition until the end of the moulting period in the first breeding season.
Carlini, A. R., H. O. Panarello, M. E. I. Marquez, G. A. Daneri and G. E. Soave (2000). Energy gain and loss during lactation and postweaning in southern elephant seal pups (Mirounga leonina) at King George Island. Polar Biology 23: 437-440.
Deuterium-labeled water was used to measure changes in the proximate body composition during the lactation period and after weaning in southern elephant seal pups at King George Island, South Shetland Islands, Antarctica. During the lactation period (23.0 ±1.4 days) pups gained a mean of 4.9 ± 0.5 kg/day (n = 7). Of the total mass gain (112 ± 8 kg), 38% was water, 48% was fat, and 11% was protein. This represented an increase in total body gross energy of 2437 ± 145 MJ. The proportion of body mass repre- sented by fat was less than 2% at birth, increasing to 35 ± 2% at weaning. We followed the pups during a mean period of 36 ± 3 days after weaning. During this period, pups had a mean loss of 1.21 ± 0.10 kg/day (n ‹ 7) comprising 39% water, 48% fat, and 12% protein. The energy cost over this period was 952 ± 168 MJ, which represented, on average, 39% of the total energy gained during the suckling period.
Carlini, A. R., M. E. I. Marquez, S. Ramdohr, H. Bornemann, H. O. Panarello and G. A. Daneri (2001). Postweaning duration and body composition changes in southern elephant seal (Mirounga leonina) pups at King George Island. Physiological and Biochemical Zoology 74(4): 531-540.
Weaning mass in southern elephant seals is highly variable, the heaviest pups being three times as heavy as the lightest ones. After weaning, pups undergo an extensive postweaning period in which they draw on their reserves. To quantify the energy expenditure during the postweaning period, changes in mass, body composition, and postweaning duration were measured in southern elephant seals at King George Island, South Shetland Islands, Antarctica. Overall, mean pup weaning mass was 154 [plus/minus] 26 kg (n = 117) and did not differ between sexes. Mean minimum postweaning duration was 42.5 [plus/minus] 7.5 d. Heaver animals at weaning had lower mass-specific mass loss rates than lighter ones, and a faster depletion of body reserves was associated with a shorter postweaning period. The proportion of body mass represented by fat at weaning was 37% [plus/minus] 4% (n = 47) and did not differ between sexes. Of these pups, 36 were recaptured after a mean period of 36 d after weaning. On average, total mass loss measured in these animals (39 kg) was composed of 39% water, 47% fat, and 12% protein. The composition of mass loss was not significantly different between sexes and was not related to weaning mass or total body energy reserves. However, fatter animals at weaning lost more fat per kilogram lost than thinner ones. Late in the fast, males and females appeared to be in a similar body condition. Nevertheless, the overall proportion of body mass represented by fat at this time was lower than that presented by the same animals at weaning. We estimated that during the postweaning period pups lost, on average, 30% of their mass at weaning. This comprised approximately 35% of the energy and 32% of the fat in the pup's body.
Carlson, K. D. and B. J. Le Boeuf (1998). Visual pigment sensitivity of the northern elephant seal. World Marine Mammal Science Conference Monaco, Lawrence, KS, Society For Marine Mammalogy.
The accurate measurement of reproductive success and verification of mating systems has critical implications for evolutionary, behavioral, and population biology. The purpose of this study was to 1) determine the relationship between the distribution of male southern elephant seal paternity and a variety of behavioral correlates, and 2) assess the accuracy of using detailed mating patterns to predict individual paternities. Research was conducted for two consecutive seasons at 2-3 study harems containing approximately 75 males and 300 females at Peninsula Valde's, Argentina. During year one, mating was observed during all daylight hours for the entire season, and all males that copulated or were regular harem attendees were tissue sampled (n=73). During year two, tissue samples were obtained from approximately 150 returning mothers and their pups. Paternity analyses (n=90) were conducted using microsatellite DNA markers and the statistical package Cervus. ANCOVA revealed two significant patterns: 1) number of paternities increased with increasing rank and estimated number of females inseminated (% copulations x number of females), and 2) number of paternities increased with increasing rank and male attendance (% of days at harem). For individual paternities, there was a significant interaction between male rank and a measure of combined copulation duration. Depending on the quality of female mating records, discriminant analysis models using one to four variables correctly predicted individual paternities with an accuracy of 74 to 81%. These findings suggest that field measures of southern elephant seal mating behavior can accurately predict general distributions of paternity. Similarly, though a variety of factors certainly play a role in fertilization, field observations can have considerable power in predicting individual paternities.
Carrick, R. and S. E. Ingham (1960). Ecological studies of the Southern Elephant seal, Mirounga leonina (L.), at Macquarie Island and Heard Island. Mammalia 34: 325-342.
Carrick, R., S. E. Csordas, S. E. Ingham and K. Keith (1962 a). Studies on the southern elephant seal, Mirounga leonina (L.). III. The annual cycle in relation to age and sex. C.S.I.R.O. Wildlife Research 7: 119-160.
Carrick, R. and S. E. Ingham (1962 a). Studies on the southern elephant seal, Mirounga leonina (L.). I. Introduction to the series. C.S.I.R.O. Wildlife Research 7: 89-101.
Carrick, R., S. E. Csordas and S. E. Ingham (1962 b). Studies on the southern elephant seal, Mirounga leonina (L.). IV. Breeding and development. C.S.I.R.O. Wildlife Research 7: 161-197.
Carrick, R. and S. E. Ingham (1962 b). Studies on the southern elephant seal, Mirounga leonina (L.). V. Population dynamics and utilization. C.S.I.R.O. Wildlife Research 7: 198-206.
Castellini, J. M., M. A. Castellini and M. B. Kretzmann (1990). Circulatory water concentration in suckling and fasting northern elephant seal pups. Journal of Comparative Physiology B Biochemical Systemic and Environmental Physiology 160: 5.
This study examined circulatory water concentrations in the neonatal northern elephant seal (Mirounga angustirostris ) to determine how suckling and fasting would alter the percentage of water in the whole blood, plasma, and red blood cells (RBC). Plasma water concentration dropped by about 3% during suckling and recovered about 1% during the fast weaning. RBC water increased about 1% during the first 2 weeks of suckling but dropped to slightly below original neonatal values by weaning. The first several weeks of fasting were marked by wide variability in RBC water, but by the end of the fast RBC water was comparable to that at weaning. These results indicate: northern elephant seal pups do not exhibit circulatory dehydration during 10 weeks of fasting and measurements of plasma or RBC metabolites (such as plasma glucose or RBC hemoglobin) may show variations or trends due not to metabolic regulation but rather to changes in circulatory water concentration.
Castellini, J. M. and M. A. Castellini (1993). Estimation of splenic volume and its relationships to long-duration apnea in seals. Physiological Zoology 66( 4): 619- 627.
Splenic volume was estimated in northern elephant seal pups (Mirounga angustirostris) by calculating the reservoir volume required to accommodate measured shifts in hematocrit that occur during periods of sleep-associated apnea. In vivo total estimated splenic mass for 15 pups represented 2.8% of body mass, while adult female seal splenic mass was estimated to be between 7.3% and 10.5% of body mass, considerably higher than that of terrestrial mammals. The model was applied to several other species of pinnipeds. Splenic mass estimates by this method were in agreement with previously reported values obtained for some pinniped species by computerized axial tomography (CT) scan. The data suggest that splenic mass in seals is correlated to the blood volume to body mass ratio and that the large spleen of seals is an anatomical consequence of the increased phocid blood volume.
Castellini, M. A. (1994). Apnea tolerance in the elephant seal during sleeping and diving: physiological mechanisms and correlations. Le Boeuf: opulation ecology, behavior, and physiology University of California Press Berkeley, Los Angeles etc 1994 i-xviii, 1-414 Chapter pagination 343-353.
Castellini, M. A., W. K. Milsom, R. J. Berger, D. P. Costa, D. R. Jones, J. M. Castellini, L. D. Rea, S. Bharma and M. Harris (1994). Patterns of respiration and heart rate during wakefulness and sleep in elephant seal pups. American Journal of Physiology 266( 3): 863-869.
Although breath holding during diving has been studied extensively in seals, the recent observation that these mammals also exhibit long-duration apnea while apparently sleeping has not been systematically examined. This project examined sleep apnea in northern elephant seal pups (Mirounga angustirostris). The animals exhibited a sequential sleep pattern of wakefulness-slow-wave sleep (SWS)-rapid eye movement (REM) sleep that resembled the normal pattern of mammalian sleep. The typical respiratory pattern during sleep in 4-mo-old pups consisted of short periods of continuous breathing separated by periods of apnea of up to 12 min. Several cycles of apnea and eupnea could occur during a single sleep episode. Breathing during a sleep cycle occurred only in SWS, never during REM sleep. The eupneic heart rate was characterized by significant sinus arrhythmia, and the apneic heart rate was similar to the minimum value during normal sinus arrhythmia. Patterns of change in breathing and heart rate associated with wakefulness and sleep were similar in seals sleeping underwater and on land. When sleeping underwater, the seals raised their heads to the surface to breathe without awakening. The changes in heart rate associated with normal sinus arrhythmia, sleep apnea, and diving apnea appear to be similar, suggesting regulation by a common homeostatic control mechanism.
Castellini, M. A., L. D. Rea, J. L. Sanders, J. M. Castellini and T. Zenteno-Savin (1994). Developmental changes in cardiorespiratory patterns of sleep-associated apnea in northern elephant seals. American Journal of Physiology 267( 5): 1294-1301.
The development of heart rate and respiratory patterns related to sleep-associated apnea were studied in northern elephant seal (Mirounga angustirostris) pups and adult males. Heart rate patterns became more refined in conjunction with an age-related increase in apnea duration in pups. That is, older pups showed significant sinus arrhythmia, while breathing and apneic heart rate were both stable and similar in magnitude to the sinus arrhythmia minimum. By contrast, younger pups showed poor or nonexistent sinus arrhythmia and shorter apnea durations with a variable and/or high heart rate during apnea. Apnea duration was positively correlated with the development of sinus arrhythmia and negatively correlated with both eupneic and apneic heart rate. Adult males showed extremely well-developed patterns of sinus arrhythmia and, in all cases, the minimum heart rate during the sinus arrhythmia was lower than the average heart rate recorded during apnea. These results suggest that seal pups are not born with the cardiac control associated with voluntary long duration apnea, but that apnea tolerance increases with refined cardiorespiratory control.
Castellini, M. A. and T. Zenteno-Savin (1997). Heart rate scaling with body mass in pinnipeds. Marine Mammal Science 13(1): 149-155.
Recent data on the diving behavior of pinnipeds have shown that some species, such as northern elephant seals (Mirounga angustirostris), can spend over 90% of their time at sea submerged under water. For these seals the most common physiological state while they are away from shore is that of breath-holding. During this time they forage, gain mass, gestate the fetus, swim, sleep, and dive. This suggests an interesting regulatory enigma in cardiac physiology. Because heart rate is lower during apnea than during eupnea and because the apneic state represents most of the time spent at sea, then it should follow that the metabolic demands of the pelagic seal (gestation, digestion, etc.) are met at the lower, diving heart rate. Under these criteria, the apneic heart rate could be considered to be the maintenance or resting heart rate for seals, and the eupneic surface heart rate could be considered tachycardia. Here the authors provide a new method of testing the theory by examining the relationship of heart rate to body mass.
Chabot, D. and G. B. Stenson (2002). Growth and seasonal fluctuations in size and condition of male Northwest Atlantic harp seals Phoca groenlandica: an analysis using sequential growth curves. Marine Ecology-Progress Series 227: 25-42.
Pinnipeds have marked seasonal changes in body condition, accumulating energy reserves prior to the reproduction period, and depleting these reserves during the breeding and molting periods. This cycle is not well described in male harp seals Phoca groenlandica, We obtained morphometric measurements for 3167 Northwest Atlantic male harp seals sampled between 1979 and 1995. The part of the yearly cycle covered in this study (November to May) was divided into short blocks around median dates called 'periods'. For each period, a growth curve was calculated for body mass, sculp mass, core mass and standard length. These sequential growth curves were used to calculate changes in size-at-age between periods, In addition, seasonal changes in 3 condition indices (general, sculp and core condition), in blubber thickness and in the ratio of sculp to total mass were analyzed using locally weighted regressions. Male harp seals returned from their high-latitude feeding grounds heavier, in better condition, and with a thicker blubber layer than when they left the area in the spring. However, maxima in length, mass, condition and blubber thickness were not observed until the February 22 period (February 12 to March 4), or in the case of seals younger than 5 yr, sometime in March. Mass losses associated with the rut began between the periods February 22 and March 15 (March 5 to 25) and were most pronounced in seals older than 10 yr. About 66% of the losses in mass came from the core during this period, We estimated that males lost 39.4 kg during the rut (1.16 kg d(-1) or 0.78 % of initial mass d(-1), 44 % from sculp and 56 % from core) and incurred energy expenditures of 840 MJ (24.7 MJ d(-1)). This corresponds to twice the standard metabolic rate (SMR), and suggests that males are feeding during the rut. All males lost mass in April, and again in May. They began to molt April 19 period (April 16 to 22). Fewer than half the seals had completed the shedding of old hair when the study ended, in the May 10 period. Rates of mass loss during the molt varied from 1 to 1.8 kg d(-1), depending on the age of the seals. Minima of length, mass, condition and blubber thickness were observed in May. Molting appears to be a period of high energy expenditures (3 to 5 SMR) despite the low levels of activity observed at this time, This study revealed that length also changes seasonally: fat seals in February were longer than lean seals of the same age in late April.
Christenson, T. E. and B. J. Le Boeuf (1978). Aggression in the female northern elephant seal, Mirounga angustirostris. Behaviour 64(1-2): 158-172.
Maternal aggressive behavior of northern elephant seals enhances reproductive success by increasing the likelihood of pup survival. Detailed observations of marked mother-pup pairs revealed that female aggressiveness increased dramatically after giving birth. Maternal aggressiveness also correlated negatively with the number of times the pup was bitten by alien females. Mothers of these pups were less aggressive than the 17 whose pups survived. Pup behavior was not directly related to mortality. Frequencies of interfemale aggressive encounters were compared for different beach areas. Aggression was most frequent on the smallest area, where interfemale distance was the shortest, and tidal action extreme. Aggression was least frequent on the sparcely populated beach, affected little by tide or male activity. Interfemale distance was greatest here. Reproductive advantages and disadvantages of pupping on each area are noted.
Clarke, M. R. and N. MacLeod (1982). Cephalopods in the diet of elephant seals at Signy Island, South Orkney Islands. BAS Bulletin 57: 27-31.
Cephalopod remains from 11 elephant seals collected at Signy Island consist mainly of 68 upper beaks and 50 lower beaks. The lower beaks were sorted and measured. Eight species in six families are present. Gonatus antarticus contributing 42%, an unidentified teuthoid (20%), Moroteuthis knipovitchi (14%) and an octopod (10%) were the most numerous species. Estimates from beak lengths show that the octopus contributed 60% of the weight of cephalopod flesh represented by beaks in this collection, while Gonatus antarcticus contributed 15% and Moroteuthis knipovitchi 10%. The species most frequently eaten are Gonatus antarcticus (44% of samples containing lower beaks) and the unidentified teuthoid (56% of samples).
Clinton, W. L. (1990). Sexual selection and the life-history of male northern elephant seals, Mirounga angustirostris. Santa Cruz, California, University of California.
Clinton, W. L. and B. J. Le Boeuf (1993). Sexual selection's effects on male life history and the pattern of male mortality. Ecology 74: 1884-1892.
Modifications of male life history due to sexual selection should be apparent in polygynous species such as elephant seals, in which sexual selection has produced a high degree of sexual dimorphism. In theory, male traits that confer a mating advantage bear survival disadvantages. The aim of this study was to examine the relationship between sexual selection and life history patterns in male northern elephant seals, Mirounga angustirostris . A life table, with age-specific estimates of mortality and reproduction, was constructed for male elephant seals from resighting data of tagged seals. Increased age-specific mortality was associated with the period of first reproduction by males, which occurred from 6-10 yr of age. A negative relationship was found between mating success and future survival in males that were beginning to breed. Older males showed no phenotypic costs to reproduction, and a positive, but not significant, relationship was shown between current mating success and future survival and mating success.
Clinton, W. L. (1994). Sexual selection and growth in male Northern Elephant Seals. Elephant seals. Population ecology, behavior, and physiology. B. J. L. Boeuf and R. M. Laws. Berkeley (CA), University of California Press: 154-168.
I studied the interactions between body size, growth, and life history in male northern elephant seals, Mirounga angustirostris, by constructing a growth curve and comparing the characteristics of growth to the pattern of male life history. The aim of this study was to determine the relationship between growth rate and agespecific male mortality rates. Four related exponential functions and a twocomponent logistic function were fitted to age-length data by nonlinear least squares regression. The two-component logistic curve fit the age and length data better than the best fitting exponential curve, the Richards function; however, both functions indicated a peak in growth rate around 3 to 5 years of age. Growth rates were high from 2 to 6 years of age, with relative growth rates of about 10% per year. Standard length of males increased each year of life until 9 years of age, and measurements of actual yearly growth indicated that after physical maturity, males stopped growing.
The peak in growth rate around 3 to 5 years of age and the end of growth by 9 years of age were related to important characteristics in the life history of males. The growth spurt may be associated with delayed maturity and a consequence of sexual selection for large body size. The timing of the growth spurt coincided with the lowest age-specific mortality rates over the life span of males and with the ages when increased growth rate was matched by longer periods of foraging at sea. Thus, the ages when males were exposed to the survival disadvantages of high growth rates were actually a period of low mortality. The high mortality among males occurred at 9 to 10 years of age after growth has ended and appeared to be associated with competition for mates.
Clutton-Brock, T. H., S. D. Albon and F. E. Guinness (1981). Parental investiment in male and female offspring in polyginous mammals. Nature 289: 487-489.
Condit, R. and B. J. Le Boeuf (1984). Feeding habits and feeding grounds of the Northern elephant seal. Journal of Mammalogy 65(2): 281-290.
Prey species consumed by northern elephant seals (Mirourga angustirostris ) were identified from the stomach and throat contents of dead seals and from observations of prey captured. Their diet consisted of a variety of pelagic, deep water squid, Pacific hake, sharks, rays, and ratfish. Feeding grounds of elephant seals were inferred from sightings of tagged elephant seals at non-rookery locations. Feeding areas extended from northern Baja California to northern Vancouver Island. Juveniles of both sexes and adult males moved north from their haul out sites in search of food, travelling furthest north during the summer. A few sightings suggested that adult females remain in the vicinity of the rookeries where they breed.
Condit, R. S. and L. C. Ortiz (1987). The physiological transition from fasting to feeding in weaned elephant seal pups. Marine Mammal Science 3( 3): 207- 219.
We studied energetics and food utilization in young elephant seals as they were first introduced to solid food following their long post-weaning fast. Using radioactive tracer techniques, we monitored changes in body composition, protein metabolism, and metabolic rate during fasting and initial feeding. In fasting animals, fat stores supplied nearly all energetic requirements. In feeding animals, 49% of protein ingested was retained as body tissue, allowing protein mass to increase. Body fat was lost at rates comparable to rates in fasting animals and continued to fuel the bulk of metabolism. Weight loss was arrested when animals consumed 786 g/d, or 40 kcal/kg^0.75/d, which was far less than their metabolic rates (63-206 kcal/kg^0.75/d). Surprisingly, the young seals were able to main- tain weight and store protein while energy intake was below metabolic needs. This was possible because animals gained weight as water; they retained well- hydrated proteinaceous tissue while losing poorly-hydrated adipose tissue. Key words: elephant seal, food utilization, food consumption, energetics.
Condy, P. R. (1977). The ecology of the southern elephant seal Mirounga leonina (Linnaeus 1758), at Marion Island. Pretoria (South Africa), University of Pretoria.
Tagging of southern elephant seals at Marion Island was carried out over four years, effort being concentrated on the pups. No long distance movement to other island groups was recorded, and no females tagged as pups matured during the three years of observations. Some tagged beachmasters maintained their status at the same sites for three consecutive seasons. Harems of 60-130 cows included an assistant beachmaster, and larger harems contained two assistant beachmasters. The breeding population (including pups) declined from 1951 to 1975, and present population size is approximately 4,500 seals. Mortality in the first and second years of life was high, with female recruitment to the third year being the apparent population limiting factor, and appeared to be the result of killer whale predation. Net reproductive rate was less than one and the mean generation interval was 6.65 years. Pup development was similar to that which occurs elsewhere, but age specific body mass and size from birth to 40 days of age were the smallest so far recorded for this species.
Condy, P. R. (1978). Distribution and abundance of southern elephant seals Mirounga leonina (Linn.) on the Prince Edward Islands. S. Afr. J. Antarct. Res. 8: 42-48.
On Marion and Prince Edward Islands, southern elephant seals occurred mainly on the leeward east and north coasts between 1973 and 1977. During the spring breeding haul-out, adults and pups remained on beaches scattered along these coasts. During the summer and autumn moult haul-out, adult and subadults arrived on the beaches and then moved inland into moulting areas, while moulting yearlings remained on the beaches. Pup counts totalled 1115 and 386 on Marion and Prince Edward Islands respectively, indicating a 69.5 per cent decline in population size on Marion Island between 1951 and 1976.
Condy, P. R., R. J. Van Aarde and M. N. Bester (1978). Seasonal occurrence and behaviour of Killer whales Orcinus orca, at Marion Island. Journal of Zoology London 184(3): 449-464.
The paper describes the occurrence of killer whales at Marion Island (Prince Edward group) in the south Indian Ocean from Aug. 1973 to Nov. 1976. They occur seasonally, being most numerous from Oct. to Dec. Their occurrence is synchronized with the seasonal haul out of Southern elephant seals, but the seasonality of King, Rockhopper and Macaroni penguins is also likely to influence their occurrence. The largest herds occur in Oct., the month during which mean group size is also largest. Sex and age composition are given, adult males being significantly more numerous than adult females, while 36.3% of the latter had calves. Hunting activity appears to be greatest between 15.00 and 17.00 hrs, and most killer whales were seen within 100 m of the shore. Aspects of hunting, attacking, feeding and resting behavior are discussed. The body measurements of a young male found on a beach are given.
Condy, P. R. (1979 a). Annual cycle of the Southern elephant seal Mirounga leonina at Marion Island. S. Afr. J. Zool. 14: 95-102.
Condy, P. R. (1979 b). Elephant seals of Marion Island. African Wildlife 33(1): 36-37.
This paper reports observations of the breeding biology and ecology of elephant seals at Marion I. and surveys the declining elephant seal population. The discussion treats breeding behavior, the parturition period, pup rearing, survival of the young and moulting. It is noted that moulting seals have a considerable localized influence on the island environment through the effects of trampling and manuring, and the effects can last for some years in the absence of further visits by the seals to the same areas. A count of elephant seals on Marion I. in Nov. 1975 revealed a decrease of 55% in the population since 1951/52. The reason for the decline is not yet clear, although predation by killer whales is suspected. Other possible factors are being investigated.
Condy, P. R. (1980). Postnatal development and growth in southern elephant seals (Mirounga leonina) at Marion Island. S. Afr. J. Wildl. Res. 10(3/4): 118-122.
Postnatal development and growth in southern elephant seals were studied at Marion Island. Weaning occurred at 22-23 days, and molting was completed at 28 days. Males became nutritionally independent at the age of 28-30 days and females at 32-34 days. There was no significant difference between body mass of males and females at birth and weaning, but from nutritional independence onwards, males were significantly heavier than females. Newborn seals decreased in mass for 2 days following birth. From 0-22 days postpartum, average daily growth in body mass was not significantly different for males and females. Comparisons with the development and growth of pups at Signy, Macquarie and Kerguelen Islands showed that at the colder more southerly islands birth mass was greater, growth in mass faster, and molting was delayed but age at weaning was unchanged.
Condy, P. R. (1982). The ecology of the southern elephant seal Mirounga leonina (Linnaeus, 1758), at Marion Island.
Condy, P. R. (1984). The population of the southern elephant seal, Mirounga leonina, at Marion Island, 1973-1983. South African Journal of Science 80(1): 26-27.
One of the most significant findings reported from the research on elephant seals at Marion Island is that their population is declining, and that these declines seem widespread across the whole southern Indian Ocean. Some common factors are suggested which could be affecting these populations, namely insufficient number of harem bulls, the killer whale effect, and competition with the rapidly recovering stocks of subantarctic fur seals.
Cooper, C. F. and B. S. Stewart (1983). Demography of northern elephant seal, 1911-1982. Science 219: 969-971.
Costa, D. P., B. J. Le Boeuf, C. L. Ortiz and A. C. Huntley (1986). The energetics of lactation in the Northern elephant seal, Mirounga angustirostris. Journal of Zoology London 209: 21-33.
Costa, D., D. E. Crocker and B. LeBoeuf (1997). The effects of low frequency sounds on pinnipeds. Stone, Gregory; Goebel: status, trends and issues A symposium of the 127th Annual Meeting of the American Fisheries Society, August 28, 1997, Monterey, California Monterey Bay Aquarium & New England Aquarium, Monterey & Boston 1997 i-vii, 1-179 Chapter pagination 95-106.
Costa, D. P., D. E. Crocker, J. Gedamke, P. M. Webb, D. S. Houser, S. B. Blackwell, D. Waples, S. A. Hayes and B. J. Le Boeuf (2003). The effect of a low-frequency sound source (acoustic thermometry of the ocean climate) on the diving behavior of juvenile northern elephant seals, Mirounga angustirostris. J Acoust Soc Am 113(2): 1155-65.
Changes in the diving behavior of individual free-ranging juvenile northern elephant seals, Mirounga angustirostris, exposed to the acoustic thermometry of the ocean climate (ATOC) sound source were examined using data loggers. Data loggers were attached to the animals and measured swim speed, maximum depth of dive, dive duration, surface interval, descent and ascent rate, and descent and ascent angle along with sound pressure level (SPL). The ATOC sound source was at a depth of 939 m and transmitted at 195 dB re: 1 microPa at 1 m centered at 75 Hz with a 37.5-Hz bandwidth. Sound pressure levels (SPL) measured at the seal during transmissions averaged 128 dB and ranged from 118 to 137 dB re: 1 microPa for the 60-90 Hz band, in comparison to ambient levels of 87-107 dB within this band. In no case did an animal end its dive or show any other obvious change in behavior upon exposure to the ATOC sound. Subtle changes in diving behavior were detected, however. During exposure, deviations in descent rate were greater than 1 s.d. of the control mean in 9 of 14 seals. Dive depth increased and descent velocity increased in three animals, ascent velocity decreased in two animals, ascent rate increased in one animal and decreased in another, and dive duration decreased in only one animal. There was a highly significant positive correlation between SPL and descent rate. The biological significance of these subtle changes is likely to be minimal. This is the first study to quantify behavioral responses of an animal underwater with simultaneous measurements of SPL of anthropogenic sounds recorded at the animal.
Cox, C. R. (1976). Reproductive strategies of northern elephant seal. Department of Psychology. Stanford, CA, University of California: 107.
Cox, C. R. and B. J. Le Boeuf (1977). Female incitation of male competition: a mechanism of mate selection. American Naturalist 111: 317-335.
Females that mate with the most fit male available leave more viable offspring than females that mate with males of lesser fitness. We describe a mechanism by which females facilitate mating with a superior genotype, as reflected by age, social rank, and sexual experience, without exerting choice. Female elephant seals increase the probability of mating with a mature, high-ranking male by simply rejecting all copulatory attempts during early estrus. Females protest loudly when mounted; this signals all nearby males and activates the dominance hierarchy. The probability that the mounting male will be interrupted by another male is a function of the mounter's social rank. The lower his rank, the higher the probability of interruption. The result is that mature males of high social rank have more time and freedom to attempt copulation, and they succeed in doing most of the mating. The behavior of the female intensifies this monopoly by making it more difficult for young, subordinate males to copulate. A similar female strategy seems to operate in several species where the female is courted by several males. Influencing the genotype of her offspring is an important means by which a female can increase her inclusive fitness. This aspect of sexual selection has been neglected.
Cox, C. R. (1981). Agonistic encounters among male elephant seals: frequency, context, and the role of female preference. American Zoologist 21: 197-209.
Crawley, M. C. (1990). Southern elephant seal. King, C M [Ed.]. The handbook of New Zealand mammals. Oxford University Press: 262-267.
Crocker, D. E., B. J. Le Boeuf, Y. Naito, T. Asaga and D. P. Costa (1994). Swim speed and dive function in a female northern elephant seal. Le Boeuf: opulation ecology, behavior, and physiology University of California Press Berkeley, Los Angeles etc 1994 i-xviii, 1-414 Chapter pagination 328-339.
Crocker, D. E., J. D. Williams, D. P. Costa and B. J. Le Boeuf (1995). Urea turnover in lactating northern elephant seals. World Marine Mammal Science Conference Orlando, Florida, Lawrence, KS, Society for Marine Mammalogy.
Crocker, D. E., B. J. Le Boeuf and D. P. Costa (1997). Drift diving in female northern elephant seals - implications for food processing. Canadian Journal of Zoology 75(1): 27-39.
We tested predictions from the hypothesis that northern elephant seals, Mirounga angustirostris, drift during the bottom segment of some dives (called C dives) using oxygen saved from reduced locomotion to process food. Sixteen free-ranging dive records were obtained with microcomputer dive recorders attached to 13 adult females from Ano Nuevo, California, during biannual foraging trips when they were in early or late stages of gestation; swim speed was recorded throughout one dive record. Body composition was measured before and after trips to sea. C dives with a bout length of 2-10 dives and a mean duration similar to those of other dive types made up 6.3 +/- 1.9% of the dives recorded. Swim speed was near or below the recorder stall speed (0.22 m/s) during the second, drift segment of these dives. The rate of vertical depth change while drifting varied little within bouts, was initially significantly correlated with the ratio of fat to lean body mass at departure, and changed systematically as the seals fed while at sea. Females in early gestation, with initial mean body fat of 24%, drifted down at a mean rate of 0.31 +/- 0.04 m/s; females in late gestation, with mean body fat approaching 36%, drifted up at an average rate of 0.17 +/- 0.05 m/s. The frequency, duration, and temporal pattern of drift dives were correlated with foraging behavior, supporting the hypothesis that drifting while diving is associated with the metabolic cost of processing food. This study provides indirect support for the hypothesis that elephant seals suspend active swimming on certain dives, during which a greater proportion of oxygen stores is allocated to the processing of food, without interrupting the seals' normal pattern of continuous diving and allowing them to remain within their aerobic dive limit.
Crocker, D. E., P. M. Webb, D. P. Costa and B. J. Le Boeuf (1998). Protein catabolism and renal function in lactating northern elephant seals. Physiological Zoology 71(5): 485-491.
Northern elephant seals, Mirounga angustirostris, fast completely from food and water during lactation. Previous investigations of maternal investment suggested physiological constraints on the level of energy expenditure during lactation. In this study, two components of phocid fasting physiology, protein sparing and reduced glomerular filtration rate, were examined for effects of changing body composition and lactation duration. Protein catabolism was estimated from 14C-urea turnover in five mid- and five late-lactation females. Body composition was determined by using an ultrasound scanner to measure blubber depth coupled with morphometrics. Glomerular filtration rate was measured in five females at mid- and late-lactation using plasma clearance of 3H-inulin. Protein catabolism increased significantly between measurements. The contribution of protein to metabolism varied with body composition and lactation duration. Mass-proportional glomerular filtration rate increased significantly between measurements. These data suggest that conflicting metabolic demands of lactation and fasting might constrain the duration and magnitude of maternal investment in northern elephant seals.
Crocker, D. E., J. D. Williams, D. R. Costa and B. J. Le Boeuf (2001). Maternal traits and reproductive effort in northern elephant seals. Ecology 82(12): 3541-3555.
The aim of this study was to determine the effects of maternal traits on reproductive expenditure and energy delivery to the offspring in a capital breeder, the northern elephant seal (Mirounga angustirostris). Changes in maternal and offspring energy reserves and milk-energy delivery were examined in relation to maternal parturition mass, body composition, and age in females and pups breeding at Ano Nuevo State Reserve, California. Maternal body mass and composition had significant effects on maternal energy expenditure over lactation. Path analysis suggested no significant effects of maternal age on reproductive effort of parous females. The efficiency of milk production increased significantly with maternal age. Offspring metabolism was a relatively small component of maternal energy expenditure, with pups storing 84% of the energy obtained from milk. These effects are an important consequence of the phocid strategy for enabling terrestrial parturition despite marine feeding. This strategy has resulted in an abbreviated and highly efficient lactation system that is strongly impacted by body reserves, linking foraging success at sea with reproductive success on land. Maternal size, body composition, and age were important features of reproduction in northern elephant seals. These characteristics are rarely considered concurrently in life history studies.
Croll, D. A., M. K. Nishiguchi and S. Kaupp (1992). Pressure and lactate dehydrogenase function in diving mammals and birds. Physiol. Zool. 65(5): 1022-1027.
Emperor penguins, elephant seals, and sperm whales have been shown to dive to considerable depths, 265 m, 1,500 m, and 1,140 m, respectively. These animals must cope with extreme changes in hydrostatic pressure as they dive. The effects of hydrostatic pressure on the Michaelis-Menten constant, K(m), of cofactor binding of NADH of muscle M4 (muscle type) lactate dehydrogenase (LDH) was measured for these diving vertebrates and compared with a nondiving mammal, the domestic rabbit. No effect of pressure changes as great as 2.066 x 104 kPa (204 atm) was observed in either the diving or nondiving species LDH preparations. Results support the hypothesis that, at least concerning the K(m) of NADH in the M4 LDH of the diving vertebrates examined, the LDHs of warm-blooded divers do not appear to be affected by changes in hydrostatic pressure and the enzyme may be preadapted for insensitivity to pressure perturbations.
Cruwys, E. and P. B. Davis (1994). Southern elephant seal numbers during moult on Livingston Island, South Shetland Islands. Polar Record 30(175): 313-314.
Southern elephant seals (Mirounga leonina) undergo an annual moulting process, in which they haul out for extended periods, during which sheets of cornified epidermis with old hairs slough off. The timing of the moult varies between geographical populations as well as sex and age groups. Hannah Point (62 degree 39'S, 60 degree 38'W) is located on the south-central coast of Livingston Island in the South Shetland Islands. During most of the austral summer it is free of snow and ice, except for the glaciers on the northern end. Hannah Point comprises a spit of land 2.1 km long, with a ridge running down the middle, flanked by beaches. The terrain is predominantly hard-packed sand with some moss beds, although the extreme southwest is comprised of flat rocks and stony beaches. Beaches and tussocky grass are the preferred haul-out sites of southern elephant seals, and although Hannah Point has no grass, there are abundant flat expanses of sand protected from off-shore winds by the central ridge. Southern elephant seal wallows occur along the entire length of Hannah Point beach. Southern elephant seals were counted daily between 2 January and 16 February 1994 along the entire length of Hannah Point beach. The count was taken between 8 AM and 10 AM by three independent observers. The sex of the animals and whether they were adult, sub-adult, or juvenile were also noted.
Cruwys, E. and P. B. Davis (1994). Moulting southern elephant seals, Mirounga leonina (L.) and local weather conditions, on Livingston Island, South Shetland Islands. Polish polar research 15(3-4): 135-146.
Molting southern elephant seals, Mirounga leonina (L.), were counted in 17 discrete wallows at Walker Bay on Livingston I. between Jan. 2 and Feb. 16, 1994. Daily weather conditions were also recorded. It was found that, although there were no overall correlations between wind scale, air temperature, sunshine, precipitation, sea roughness or cloud cover with seal numbers, there were conditions on specific days that affected the movements of seals between wallows. Most notably, it was found that numbers of seals decreased when they were exposed to winds, and that they often sought out more sheltered sites nearby.
Cruwys, E. and P. Davis (1995). The effect of local weather conditions on the behaviour of moulting southern elephant seals, Mirounga leonina (L.). Polar Record 31(179): 427-430.
The behaviour of southern elephant seals, Mirounga leonina (L.) during the breeding season has been extensively documented, and recent interest has been generated in the annual moulting process in terms of energy expenditure. During this energy-demanding period pinnipeds often exhibit listless and ill-tempered behaviour, primarily due to the physiological disturbances occurring during the moult (such as the high peripheral temperature required, reduction in resting metabolic rate, and the fasting or near-fasting conditions observed by some pinnipeds. The aim of this note is to document behaviour observed in a pod of moulting elephant seals, 1-21 January 1994 at Hannah Point, Livingston Island, South Shetland Islands, in relation to local weather conditions.
Cruwys, E. and P. B. Davis (1995). Moulting juvenile male southern elephant seals Mirounga leonina (L.) at Hannah Point, Walker Bay, Livingston Island, South Shetland Islands. Polar Research 14(3): 329-333.
Southern elephant seals were counted at seventeen discrete moulting sites at Hannah Point, Walker Bay on Livingston I. in the South Shetland Is. between Jan. 2 and Feb. 16, 1994. The physical characteristics of each moulting site were assessed. Counts through 46 consecutive days demonstrated that the number of juvenile males in dry moulting sites increased as the muddy wallows were gradually abandoned. This pattern of behavior is similar to that described for other sex- and age-groups (e.g. adult females) in previous studies.
Cruwys, E. and A. E. Friday (1995). A comparative review of condylobasal lengths and other craniometric characters in 30 species of pinniped. Polar Record 31(176): 45-62.
The condylobasal length (CBL) of skulls from 999 sexually mature seal, sealion, and fur seals of 30 different species was measured. Additional data gathered from previous studies are also included to give an indication of variation within each species, particularly where there is a wide geographical dispersion. Where possible, means and ranges of CBL were given separately for each sex, so that the degree of sexual dimorphism could be assessed. Previous studies have indicated that CBL continues to increase after sexual maturity has been reached. In order to assess this, three species (Mirounga leonina, Otaria byronia (flavescens), and Haliochoerus grypus) that contained individuals of known age were included in the study. Other craniometric characters are often expressed as a percentage of CBL when assessing taxonomic relationships. Some of these characters were reassessed using the new data.
Csordas, S. E. (1966). Congenital penis malformation in southern elephant seals (Mirounga leonina L). Journal of Mammalogy 47(4): 731-733.
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Dailey, M. D., M. Haulena and J. Lawrence (2002). First report of a parasitic copepod (Pennella balaenopterae) infestation in a pinniped. J Zoo Wildl Med 33(1): 62-5.
An infestation by the parasitic copepod Pennella balaenopterae was found in a stranded, 8-mo-old, female northern elephant seal (Mirounga angustirostris). Diagnosis was based on the finding of the cephalothoraxes of 14 adult female copepods from three subcutaneous sites. Bacteria cultured from lesion exudate included Arcanobacterium phocae, Escherichia coli, Edwardsiella tarda, an Enterococcus sp., and Proteus mirabilis. The lesions were drained and irrigated with chlorhexidine, and the seal was treated with a subcutaneous injection of ivermectin. The seal recovered and was released after 43 days.
Daneri, G. A. and A. R. Carlini (1996). Stomach flushing: an adequate non lethal method for the study of elephant seal's diet. Contribuciones del Instituto Antartico Argentino 452: 1-7.
Daneri, G. A., A. R. Carlini and P. G. K. Rodhouse (2000). Cephalopod diet of the southern elephant seal, Mirounga leonina, at King George Island, South Shetland Islands. Antarctic Science 12(1): 16-19.
In the summer of 1995/96, 25 southern elephant seals, Mirounga leonina, were stomach lavaged at Stranger Point, King George Island, South Shetland Islands. Cephalopod remains were present in 72% of the individuals sampled (n = 18). Seven species of squid and three of octopus were identified. The squid Psychroteuthis glacialis was the most important prey in terms of numbers (77%), biomass (80.8%) and frequency of occurrence (94.4%). Next in importance in terms of mass was the squid Alluroteuthis antarcticus (7.8%) in the diet of females and the octopodid Pareledone ?charcoti in the diet of males (13.2%). Females preyed on a wider variety of squid taxa than males (7 vs 3) but octopodids occurred only in stomach contents from males. The predominance of P. glacialis in the prey of the South Shetland Islands elephant seals can be explained by the southerly location of the foraging areas of this population compared to South Georgia, Heard and Macquarie islands, where the diet of southern elephant seals has previously been analysed. Psychroteuthis glacialis is the predominant squid in waters close to the Antarctic continent.
Daszak, P., A. A. Cunningham and A. D. Hyatt (2000). Conservation conundrum. Response. Science 288(5475): 2320.
Davis, R. W., L. A. Fuiman, T. M. Williams and B. J. Le Boeuf (2001). Three-dimensional movements and swimming activity of a northern elephant seal. Comparative Biochemistry and Physiology Part A Molecular & Integrative Physiology 129A(4): 759-770.
We attached a video system and data recorder to a northern elephant seal to track its three-dimensional movements and observe propulsive strokes of the hind flippers. During 6 h of recording, the seal made 20 dives and spent 90% of the time submerged. Average dive duration, maximum depth and swimming speed were 14.9 min[plus/minus]6.1 S.D., 289 m[plus/minus]117 S.D. and 1.1 m s-1[plus/minus]0.12 S.D., respectively. The distance swum during a dive averaged 925 m[plus/minus]339 S.D., and the average descent and ascent angles were 41[degree][plus/minus]18 S.D. and 50[degree][plus/minus]21 S.D., respectively. Dive paths were remarkably straight suggesting that the seal was navigating while submerged. We identified three modes of swimming based on the interval between propulsive strokes: continuous stroking; stroke-and-glide swimming; and prolonged gliding. The seal used continuous stroking from the surface to a mean depth of 20 m followed by stroke-and-glide swimming. Prolonged gliding started at a mean depth of 60 m and continued to the bottom of dives. For dives to depths of 300 m or more, 75% of the descent time was spent in prolonged gliding and 10% in stroke-and-glide swimming, amounting to 5.9-9.6 min of passive descent per dive. Average swimming speed varied little with swimming mode and was not a good indicator of propulsive effort. It appears that the seal can use prolonged gliding to reduce the cost of transport and increase dive duration. Energetically efficient locomotion may help explain the long and deep dives that routinely exceed the theoretical aerobic dive limit in this species.
De Ferrer, P. A. R., R. A. G. Colaso, M. E. I. Marquez, A. R. Carlini, D. F. Vergani and G. A. Daneri (1996). Southern elephant seal (Mirounga leonina). Polar. Biol. 16(4): 241.
deLong, R. L. (1978). Northern elephant seal. Haley, D [Ed.]. Marine mammals of eastern north Pacific and Arctic waters. Pacific Search Press: 1-256 Chapter pagination 206-211.
DeLong, R. L. and B. S. Stewart (1991). Diving patterns of northern elephant seal bulls. Marine Mammal Science 7(4): 369-384.
We used small microprocessor-based, time-depth recorders to document the diving patterns of six adult male northern elephant seals (Mirounga angustirostris) from San Miguel Island, California. The recorders stored measurements of hy- drostatic pressure every 30 or 60 set while the seals were at sea for 107 to 145 d in spring and early summer; collectively, over 36,000 dives were recorded. Seals dove continually while at sea, most often to depths of 350-450 m although two seals had secondary modes at about 700-800 m; maximum depths for two seals of 1,333 m and 1,529 m are the deepest yet measured for air-breathing vertebrates. Seals were submerged about 86% of the time they were at sea, rarely spending more than 5 min at the surface between dives; 99% of all post- dive surface intervals were shorter than 10 min. Dives averaged 21-24 min, the longest was 77 min. The uninterrupted patterns of long dives punctuated by brief surface periods suggest that most if not all dives were well within these seals’ aerobic limits. Dives of bulls were, on average, about 18% longer than those published earlier for cows, evidently because of the substantially greater body mass of bulls and allometric scaling of dive endurance. Dive depths and dive durations varied seasonally; depths were greatest in spring, durations greatest in early summer. During each season dives were deepest during the day and shallowest at night except for the sixth seal whose consistently shallow dives (50-150 m) in spring were independent of time of day. Prey remains recovered by lavage from seals’ stomachs were primarily of vertically migrating, epi- and meso-pelagic squid. The diel patterns in dive depths suggest that five seals dove to and foraged in the offshore mesopelagic zone, pursuing those vertically mi- grating prey. The sixth seal behaved similarly in early spring and early summer but may have foraged in nearshore epibenthic habitats in spring.
Key words: pinnipedia, northern elephant seal, Mirounga angustirostris, time- depth recorder, diving patterns, foraging ecology.
Deutsch, C. J., M. P. Haley and B. J. Le Boeuf (1989). Dominance rank and reproductive effort in male northern elephant seals (abstract). American Zoologist 29(4): 68A.
Deutsch, C. J. (1990). Behavioral end energetics aspects of reproductive effort of male northern elephant seals (Mirounga angustirostris). Santa Cruz (CA), University of California.
Reproductive effort (RE) of male northern elephant seals was studied over four breeding seasons at Ano Nuevo, California, with the aim of measuring the costs of mating in energy, time, and risk currencies in a highly polygynous mammal. RE was expected to increase with age, dominance rank, and harem size. Unrestrained males were weighed on a platform scale two or more times over the breeding season. Adult males weighed up to 2300 kg upon arrival at the rookery. Mean rate of mass loss was 7.1 plus or minus 1.5 (SD) and 4.6 plus or minus 0.8 kg per day for 17 adults and 13 subadults, respectively. Adult males lost a mean of 36% (range, 20-50%) of their mass over the three-month breeding season. Nearly all males were wounded, but few male-inflicted injuries were debilitating and fight-related mortality was rare. High dominance enhanced mating success but was associated with an elevated mass-specific rate of mass loss and a faster depletion of the blubber layer, relative to low-ranking adults. This energetic cost was attributed to higher levels of sexual activity, greater vigilance, and reduced time in energy-conserving sleep apnea by high-ranking males. Duration of breeding effort (mean = 88 days) was not correlated with dominance rank. High-ranking males, on average, invested a slightly greater RE (percent mass lost over season) than low-ranking males. Male RE increased from 4 to 6 years of age; 6-7 year-old males were still growing but exhibited a similar RE (percent mass loss, duration of stay, and activity level) as low-ranking adults, perhaps to gain experience in social skills vital for future reproductive success, rather than for immediate fitness gains. Males adjusted their RE within a season according to spatial and temporal variation in expected reproductive benefits. Males were more active and apparently took greater risks at larger harems and during the period of peak female abundance. Male activity did not differ between day and night, but agonistic and locomotory activities were depressed during warm weather due to thermoregulatory constraints. In conclusion, male RE was flexible within a breeding season and across years, being highest when males had the best change of mating. (DBO)
Deutsch, C. J., M. P. Haley and B. J. Le Boeuf (1990). Reproductive effort of male Northern elephant seals: Estimates from mass loss. Canadian Journal of Zoology 68: 2580-2593.
The energetic component of reproductive effort of male northern elephant seals, Mirounga angustirostris, was estimated from mass loss over the breeding season and correlated with dominance rank and age. Fifty-four unrestrained bulls were weighed on a platform scale by luring them with a model of a female seal or moving them with a tarpaulin and using playback of male aggressive vocalizations. Adult males weighed up to 2300 kg upon arrival at the breeding rookery. Mean rate of mass loss during the breeding season was 7.1 ± 1.5 (SD) and 4. 6 ± 0. 8 kg per day for 17 adults and 13 subadults, respectively . Rate of mass loss was positively correlated with body size (mass or length) for both age-classes. Mass-specific rate of mass loss did not differ as between age-classes but increased with increasing dominance rank among adult males. Reproductive effort, expressed as percentage of body mass lost over the 3-month breeding season, was greater for high-ranking bulls (mean 41.4%) than for low-ranking adults (33.8%), but was not related to age-class or body size. High-ranking males experienced higher mating success and expended more energy than subordinate males. Comparison with a previous study on conspecific females indicates that mass-specific energetic investment in reproduction is similar for both sexes, despite marked sex differences in reproductive strategy and duration of effort.
Deutsch, C. J., D. E. Crocker, D. P. Costa and B. J. Le Boeuf (1994). Sex- and age-related variation in reproductive effort of Northern Elephant Seals. Elephant seals. Population ecology, behavior, and physiology. B. J. L. B. R. M. Laws. Berkeley (CA), University of California Press: 169-210.
The aim of this study was to determine how reproductive effort (RE) varies with age and sex in the northern elephant seal, Mirounga angustirostris. RE is an important feature of life history that links the proximate costs with the fitness costs of reproduction. Percentage of mass lost over the breeding season provided an energetic index of RE because both sexes fast on the rookery. We summarize research conducted over an 11-year period at Ano Nuevo, California. Seventy-three females ranging in age from 3 to 12 years were chemically immobilized and weighed during the lactation period, providing 22 measurements of maternal mass loss. Males ranging in age from 5 to 13 years were weighed (N = 56), or their mass was estimated using a photogrammetric technique (N = 94), yielding 87 measurements of breeding mass loss. The principal findings were as follows. 1. The magnitude of RE was similar between males and females. Adults of both sexes lost slightly more than one-third of their mass, on average, despite large sex differences in reproductive strategy and body size. Adult males were an average of 1.4 times longer and 3 to 4 times heavier (mean ± SD = 1,814 i 233 kg, range = 1,430-2,550 kg) than adult females (488 ± 80 kg, range = 360-710 kg) at the start of the breeding season. Male mating effort was more variable than female parental effort, and some bulls lost up to half of their arrival mass. The timing and intensity of RE differed between the sexes: males fasted three times longer than females, but they incurred less than one-third the mass-specific mass loss rate offemales. Males suffered vastly more external injuries from conspecifics than did females, yet females were probably at greater risk of receiving life-threatening internal injuries. 2. Female effort during lactation was not correlated with maternal age or mass, but gestation effort (i.e., relative neonatal mass) declined with increasing maternal mass. Absolute measures ofinvestment in offspring-including maternal mass loss, neonatal mass, weanling mass, and pup mass gain-were directly proportional to maternal mass, which increased from 3 to 6 years of age before reaching an asymptote. Maternal investment in sons was similar to that in daughters. 3. Males delayed serious efforts at mating until age 6, two to three years later than females but still physically immature, and mean RE was subsequently constant with age. Dominant males devoted a greater proportion ofbody stores to breeding and obtained higher mating success than did subordinates.
The similarity in RE of growing "subadults" and physically mature breeders for both sexes was contrary to theoretical expectations, considering the poorer reproductive success and higher fitness costs ofthe former. Possible explanations include the existence of a threshold RE below which fitness costs are minimal, the higher fitness benefit of early-born offspring in an expanding population, and the benefit ofexperience to future reproductive performance.
Dickinson, A. B. (1967). Tagging elephant seals for life-history studies. Polar Rec. 13(85): 443-446.
Dickinson, A. B. (1989). Demise of elephant sealing at South Georgia, 1960-1968. Polar Record 25(154): 185-190.
Uncontrolled sealing for furs and oil began on South Georgia about 1786 and continued sporadically until the early 20th century. From 1909 onward legislation covered licensed killing of male elephant seals Mirounga leonina. This provided for a successful oiling industry that lasted almost 60 years, operated by whalers primarily in early spring before the whaling season began. Biological research ensured that quotas in the last decade remained within the carrying capacity of the stocks. High-grade seal oil enhanced revenues from whaling, providing overall 16% of the volume and 19% of the value of total annual catches, with much higher proportions in some seasons. The seal oil industry did not long survive the demise of whaling on South Georgia, finally ending in 1968.
Dong, J., G. Wang and Z. Xiao (1993). Morphological anatomy and measure of larynx of the southern elephant seal. Mar. Sci./Haiyang Kexue 3(3): 48-51.
Downes, M. (1996). Indexing sealers' logbooks from Heard Island. Anare(Australian National Antarctic Research Expeditions): i-iv, 1-96.
Drehmer, C. J., J. Ferigolo and E. S. Borsato (1998). Occurrence of Mirounga leonina Linnaeus (Pinnipedia, Phocidae) from southernmost Brazil: Injury and pathologies. Revista Brasileira de Zoologia 15(4): 1061-1068.
A male specimen Mirounga leonina Linnaeus, 1758 age estimated between 7-8 years old, collected at Santa Vitoria do Palmar, Rio Grande do Sul State, southernmost Brazil (32 degree 44'S and, 53 degree 22'W) is presented. All the skeleton was recovered except the rostral region. It shows an advanced osteomyelitis in the left dentary, extending from the synfisis until the middle portion of the body; as well as Scheuermann disease at lumbar vertebrae. Such diseases could explain its presence at that locality, where it was shot. The bullet was recovered from the rostrum, and might be responsible for death. This is the first virtually complete skeleton of M. leonina recovered from Brazilian coast.
Drozdz, J. (1987). Oocysts of six new Coccidiomorpha species from pinnipeds of King George Island (South Shetlands, Antarctic). Acta protozoologica 26(3): 263-266.
A coproscopical examination of faeces samples in 5 species of pinnipeds from King George I. revealed the occurrence of oocysts of six new Coccidiomorpha species. Specific names are given to three more frequent and numerous species for which a process of sporulation has been observed. The following species were found: Isospora miroungae sp. n. in young elephant seals (Mirounga leonina), Eimeria sp. 1 in crabeater seal (Lobodon carcinophagus) and Eimeria weddelli sp. n., E. arctowskii sp. n., Eimeria sp. 2 and Eimeria sp. 3 in Weddell seal (Leptonychotes weddelli). In the leopard seal (Hydrurga leonina) and the eared seal (Arctocephalus gazella) no coccidian parasites have been found.
Dziurdzik, B. (1989). Hair histological structure in southern elephant seals Mirounga leonina (Linnaeus 1758) (Pinnipedia, Mammalia). Przeglyad Zoologiczny 33(3): 449-452.
The paper contains a histological description of the hair of the southern elephant seal, Mirounga leonina (Linnaeus, 1758) (Pinnipedia, Mammalia). The material used in this study was collected in the years 1978-79 in the Antarctic. The hair of the southern elephant seal contains no medulla, it is short and tape-like flattened, with mosaic cuticular scale pattern and a narrow, elliptical cross-section. It is a shield hair. Distinct differences in the histological structure of the hair between the southern elephant seal and other Pinnipedia, especially Otariidae, were found. The structure of the hair was studied by means of a light microscope (structure of hair medulla) and a scanning microscope (pattern of cuticular scales).
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Elliott, J. M. and B. J. Le Boeuf (1998). Does weaning weight predict reproductive success of female northern elephant seals ? World Marine Mammal Science Conference Monaco, Lawrence, KS, Society for Marine Mammalogy.
The aim of this study was to test the hypothesis that lifetime reproductive success of northem elephant seals, Mirounga angustirostris increases with weaning weight, i.e., the quantity of maternal energy investment. A total of 926 pups were weighed after weaning (approximately 28 days of age) over an eleven year period from 1980 to 1991, at Ano Nuevo, California. Mean weaning weight was 131.1 +/- 26.0 kg and the range was 32.5 to 218.5 kg. Weaning weight did not affect age at primiparity (mean = 4.1 +/- 0.8) or the number of progeny females produced or weaned in healthy condition. These results lead us to reject the hypothesis that lifetime reproductive success varies as a function of weaning weight, which is counter to what one would expect based on the parental investment theory.
Elson-Riggins, J. G., L. Al-Banna, E. G. Platzer and I. Kaloshian (2001). Characterization of Otostrongylus circumlitus from Pacific harbor and northern elephant seals. Journal of Parasitology 87(1): 73-78.
Otostrongylus circumlitus (Railliet, 1899) from Pacific harbor seals (Phoca vitulina richardsi) and northern elephant seals (Mirounga angustirostris) were examined using morphological and molecular methods to determine whether northern elephant seals along the central California coast are infected by the same species of Otostrongylus as are Pacific harbor seals in the same area. Fixed nematodes were examined and measured using light microscopy. The polymerase chain reaction (PCR) was used to amplify and sequence the second internal transcribed spacer (ITS-2) and D3 expansion (26S) regions of ribosomal DNA of O. circumlitus from Pacific harbor and northern elephant seals. The ITS-2 region was also amplified from Parafilaroides sp. from the Pacific harbor seal, northern elephant seal, and California sea lion (Zalophus californianus) and used for restriction fragment length polymorphism (RFLP) analysis. Morphologically, it was not possible to distinguish O. circumlitus from Pacific harbor and northern elephant seals, and over a consensus length of 443 base pairs (bp) for ITS-2 and 321 bp for D3 the sequences of O. circumlitus from both hosts were identical. With the PCR-RFLP assay, it was possible to distinguish O. circumlitus from Parafilaroides sp. The results suggest that O. circumlitus is the same species in Pacific harbor and northern elephant seals, and molecular methods make it possible to distinguish this nematode from related nematodes.
Engelhard, G. H., S. M. J. M. Brasseur, A. J. Hall, D. J. Slip, H. R. Burton, M. A. Fedak and P. J. H. Reijnders (1998). Effect of disturbance on pup weaning mass in southern elephant seals. World Marine Mammal Science Conference Monaco, Lawrence, KS, Society for Marine Mammalogy.
Quantifying the effects of disturbance on breeding biology of southern elephant seals. Mirounga leonina, is considered necessary for management and monitoring of human impacts on (Sub)Antarctic ecosystems. We monitored a number of potential behavioural and physiological measures of disturbance. It was hypothesized that disturbance would have a negative effect on the mother-pup energy transfer resulting in lower masses of pups at weaning. This paper describes the effect of handling on pup weaning mass. On Macquarie Island, 30 mother-pup pairs were given different degrees of experimental disturbance. Three experimental groups of 8, 4 and 6 pairs were captured, respectively, 3, 4 and 5 times throughout the lactation period around days 2, 11, (14, 18) and 21 post partum; a control group of 12 pairs was only captured on the 21st day post partum, one of the last days of lactation. Captures included anaesthetizing the mother and physically restraining the pup, taking blood and milk samples and measuring weight and length. Weaning masses of pups, corrected for maternal length, were significantly different among the four groups (Kruskal-Wallis H=11.9, df=3, P<0.0l). Remarkably, this difference was largely due to the most intensely treated group captured 5 times (mean 98 kg ± 18 S.D.); weaning masses did not vary significantly (Kruskal-Wallis H=I.8, df=2, P>0.05) between the control group (mean 125 kg ± 29 S.D.) and the experimental groups captured 3 times (mean 119 ± 15 S.D.) and 4 times (mean 125 ± 16 S.D.). As there is evidence of an association between weaning mass and juvenile survival (C.R. McMahon, pers. comm.), the effect observed would imply an adverse fitness effect of disturbance. Additional data on behaviour, blood stress parameters, milk composition and survival rate are needed to study the mechanism by which disturbance may affect weaning mass and survivorship and to what extent.
Engelhard, G. H., J. van den Hoff, M. Broekman, A. N. J. Baarspul, I. Field, H. R. Burton and P. J. H. Reijnders (2001). Mass of weaned elephant seal pups in areas of low and high human presence. Polar Biology 24: 244-251.
Engelhard, G. H., A. N. J. Baarspul, M. Broekman, J. C. S. Creuwels and P. J. H. Reijnders (2002). Human disturbance, nursing behaviour, and lactational pup growth in a declining southern elephant seal (Mirounga leonina) population. Canadian Journal of Zoology 80(11): 1876-1886.
We studied lactation behaviour in relation to pup growth in southern elephant seals (Mirounga leonina) at Macquarie Island, and compared harems in areas of high and low human presence to determine if there is an effect attributable to human activities, including scientific research. Pup weaning mass, a known correlate of first-year survival, was positively influenced by suckle bout durations during early and middle lactation and by maternal aggression during late lactation; no other behavioural variables were associated with weaning mass. In the area of high human presence, we observed from a distance the behaviour of mother-pup pairs directly before, during, and after visits to harems by other researchers. Alertness was raised threefold in the presence of people but quickly returned to predisturbance levels after their departure; there were no significant short-term effects on other behavioural variables. In the areas of high and low human presence, we observed the undisturbed behaviour of the seals in the absence of other people. No significant differences in any behavioural variables examined were found, indicating no long-term changes in behaviour resulting from human presence. Human disturbance therefore appears not to have significantly contributed to the population decline observed at Macquarie Island, but the conclusion requires caution given the fairly low power of our analyses.
Engelhard, G. H., S. M. Brasseur, A. J. Hall, H. R. Burton and P. J. Reijnders (2002). Adrenocortical responsiveness in southern elephant seal mothers and pups during lactation and the effect of scientific handling. Journal of Comparative Physiology B 172(4): 315-28.
We examined the cortisol responses to chemical and physical restraint stress in southern elephant seal Mirounga leonina females and their pups at three stages during lactation. In anaesthetised females the serum cortisol levels changed moderately during the 45-min sampling period following restraint, with average peaks at 23 min after anaesthetic administration. Overall, cortisol was relatively low 2 days postpartum and increased throughout lactation. In physically restrained pups serum cortisol increased rapidly after capture; the response was milder at age 2 days than at 11 days and 21 days. Levels were higher in female pups than in males. In order to test whether cortisol levels and/or responses became chronically (i.e. days to weeks) altered due to restraint, we compared the cortisol response at a late stage of lactation between three groups of mother-pup pairs previously given different levels of chemical (mothers) or physical (pups) restraint stress: control (not handled previously), moderate treatment (previously handled twice), and high treatment (previously handled 3-4 times). Pups of the three treatment groups showed similar adrenocortical responses suggesting no chronic effect of repeated physical restraint, despite the clear acute effects. Mothers of the control and moderate treatment groups showed similar cortisol responses; however, mothers of the high treatment group showed significantly attenuated responses. This indicated that elephant seals tolerated moderate degrees of handling disturbance; however, repeated (3-4) chemical immobilisations in lactating females may reduce their adrenocortical responsiveness for a period of days or weeks.
Engelhard, G. H., A. J. Hall, S. M. Brasseur and P. J. Reijnders (2002). Blood chemistry in southern elephant seal mothers and pups during lactation reveals no effect of handling. Comp Biochem Physiol A Mol Integr Physiol 133(2): 367-78.
Serum clinical chemistry parameters were examined in lactating southern elephant seal Mirounga leonina mothers and their pups from the declining Macquarie Island population. There were significant changes in serum values from 2 to 21 days postpartum in both nursing mothers (increase: inorganic phosphate; decrease: creatinine, potassium, chloride, cholesterol, total protein, albumin, globulin, aspartate aminotransferase, creatine kinase) and suckling pups (increase: inorganic phosphate, globulin, cholesterol; decrease: albumin, alkaline phosphatase, gammaglutamyl transferase; increase followed by decrease: triglycerides, iron). We found no evidence that changes were due to chronic stress effects caused by repeated chemical immobilisations (mothers) or physical restraint (pups): at late lactation, clinical chemistry values were similar for mother-pup pairs of a control group (not handled previously), moderate treatment group (previously handled twice) and high treatment group (previously handled three to four times). We were not able to detect differences in clinical chemistry values between mother-pup pairs distributed over two areas differing in the frequency of human visits. The clinical chemistry values presented here can serve as reference ranges to allow future comparison with other southern elephant seal populations to investigate factors, e.g. food limitation, suspected to be involved in population declines.
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Fabiani, A. (1996). Aspetti strutturali e funzionali del comportamento agonistico maschile nell' elefante marino del sud (Mirounga leonina) [Structural and functional aspects of male agonistic behaviour in southern elephant seals (Mirounga leonina)]. BAU. Roma, Italy, Università degli Studi di Roma "La Sapienza".
The target of this research project is the agonistic behaviour of southern elephant seals (Mirounga leonina) of two local populations of the South Georgia stock, Punta Delgada (ValdŽs Peninsula, Patagonia - Argentina) and Sea Lion Island (Falkland Islands). Each population was studied for two breeding seasons with almost the same protocol for animal marking, collection of demographic data, behavioural observations and collection of measures of structural phenotype. Firstly, I analyse both the fine structure of behaviour (action patterns and behavioural sequences) and its results at individual level (indices of behavioural performance). I analyse the effect of both structural components of phenotype (age, size, morphology) and behavioural indices (aggressiveness, dominance, role) on the structure of agonistic behaviour. I then explore the functional effects of performance in inter-male competition by evaluating the relationships between various indices of performance (interaction rate, local rank, global dominance) and indices of breeding success (control of females, mating success, fertilization success). Male agonistic behaviour in southern elephant seals comprises two components, conventional assessment and direct aggression and are both very important in the establishment and maintenance of dominance relationships. Assessment through visual and acoustic threats is more frequent than direct aggression. It is used to settle the majority of the contests, especially between males with large differences in resource holding potential (RHP). Aggression through direct interaction with physical contact and long all out fight, although less frequent, is of crucial importance in the initial phase of settlement of dominance relationships between males with almost equal RHP. Specific tactics and strategies of competition adopted by individual males are well correlated with both structural and behavioural phenotype. Variance in behavioural performance between males is very large (larger than the one measured for simple structural traits) and its distribution is different between the two populations. Hence, the relative importance of various components of phenotype seems to differ between PD and SLI. In particular, the variation of structural RHP is larger on SLI and behavioural performance has a stronger effect on male breeding performance in the SLI population. A large variation in the demography and socionomy of breeding areas and groups is present both in and between populations. The specific breeding situation has a significant effect on the relationship between performance in competition and breeding success, but the same basic trend is present in all places. Results of agonistic interactions set up dominance hierarchies, and these hierarchies are long lasting and strongly linear, both at local and population level. Excellent performance in competition between males is a fundamental requisite to high breeding success, however the local variation of parameters like breeding sex ratio and density of competitors mold the strength of this link. Stochastic factors, and factors with a deterministic nature but almost unpredictable by individual males, changes the rewards of effective competition tactics in different areas.
Fabiani, A., F. Galimberti and A. R. Hoelzel (2001 a). Male reproductive success in southern elephant seals (Mirounga leonina): behavioural estimates and genetic paternity. 15th Annual Conference of the European Cetacean Society, Roma, Italy.
The southern elephant seal (Mirounga leonina) is one of the most polygynous species of all mammals and its mating system thought to be among the purest forms of harem defence polygyny. Molecular methods provide the opportunity to reassess mating systems from a genetic perspective and to gain accurately estimates of reproductive success. Reproductive success is a fundamental component of fitness and its estimation a major problem in behavioural and evolutionary biology. In this study we estimate paternity in a population of southern elephant seals using microsatellite DNA analysis and we evaluate the relationships between observational and genetic measures of male mating success. The research was carried out on Sea Lion Island (52¡26'S; 59¡05'O), Falkland Islands, and samples for this study were collected during three breeding seasons, from 1996 to 1998. In total, 104 males and 192 mother/pup pairs belonging to seven harems (range dimension = 18 - 91 females) were typed for 9 microsatellite loci. All the sampled seal were marked and behavioural estimates of male mating success were based on records obtained with standard observation techniques. Behavioural data indicate that a small proportion of males (about 30% of all) achieved at least one copulation and, among males that copulated, the copulation distribution is highly asymmetric, indicating a strongly polygynous mating system. Genetic results also show a very high level of polygyny. Within each harem the alpha male was the male with the highest proportion of copulations (for seven harem: mean proportion = 0.80; range = 0.4 - 0.92). In each case behavioural observations were strongly supported by genetic results
Fabiani, A., F. Galimberti and A. R. Hoelzel (2001 b). Reproductive success in male southern elephant seals of Sea Lion Island (Falkland Islands): behavioural estimates and paternity. 14th Biennial Conference on the Biology of Marine Mammals, Vancouver, Canada.
The aim of the study was: a) to estimate paternity using DNA markers; b) to assess variance in male reproductive success and c) to evaluate the relationship between observational and genetic measures of male success. Samples were collected during three breeding seasons (1996 to 1998). In total, 104 males and 192 mother/pup pairs belonging to seven harems (23-104 females) were typed for 9 microsatellite loci; 356 copulations were recorded and the harems observed for a total of 1,030 hours. There were 4-10 alleles per locus, sufficient to identify paternity with a very small probability of error. We were able to assign a genetic father to 96.4% of the pups and the distribution of paternities indicated a very high level of polygyny. Behavioural indices of breeding success were very good predictors of the relative male reproductive success (r2 0.79-0.99). Even simple indices predicted genetic paternity 68-79% of the time, with behaviours associated with first copulation and association during oestrus being somewhat better than harem holding or ENFI (index of fertilization success). Within each harem, the harem holder achieved the highest proportion of paternities (mean 72%; range 48%-95%), regardless the size of the harem. Harems holders were on average more successful than those seen either in Argentina (58%) or for northern elephant seal at A–o Nuevo (38%). This suggests a difference that could relate either to male or female strategy, or to environmental factors at Sea Lion Island. Possible explanations include a general proximity of oestrus females to the sea due to the lack of a large tidal range (and consequently a lower female interception rate by peripheral males during departures), more efficient female control by the harem holders, or a more pronounced difference in resource holding potential among males.
Fabiani, A. (2002). Male reproductive success in southern elephant seals (Mirounga leonina): behavioural estimates and genetic paternity. Department of Biology. Durham, UK, University of Durham.
Fabiani, A., F. Galimberti, S. Sanvito and A. R. Hoelzel (2004). Extreme polygyny among southern elephant seals at the Falkland Islands: behavioral estimates and genetic paternity. Behavioral Ecology 15(6): 961-969.
Elephant seals are known from long-term behavioral studies to be highly polygynous and to show high variance in reproductive success among males. However, genetic studies have determined that the level of polygyny varies between the closely related northern and southern elephant seals. In the present study, we investigate paternal success at the Sea Lion Island southern elephant seal colony in the Falkland Islands by using both behavioral measures and genetic markers. We find that the average success of harem holding males at Sea Lion Island is significantly higher than both the northern species and the nearby southern elephant seal population at Punta Delgada. We compare genetic paternity with various behavioral indices of male mating success, and we find that the behavioral measures provide a good estimate of the variance in male reproductive success. Only 28.2% of males achieved paternities, and among these, harem holders accounted for 89.6%. We discuss the implications of our results in the context of the demographic and physical environment. Specifically, a comparatively high variance in resource holding potential among males, differences in male social behavior, and a small tidal cycle limiting peripheral male access during female departure from the harem at this colony may be important factors leading to the comparatively high variance in male reproductive success at Sea Lion Island.
Key words: elephant seal, Falklands, mating success, microsatellites, Mirounga, paternity, polygyny.
Falabella, V., M. Lewis and C. Campagna (1993). Revisión de aspectos demográficos del elefante marino en Patagonia, 1982-1992. XVI Reunión Argentina de Ecologia
Falabella, V. and C. Campagna (1999). Behaviour of southern elephant seal weanlings during the post-weaning fast in Patagonia. Mammalia 63(3): 257-272.
Falabella, V., C. Campagna and M. Lewis (1999). Electrocardiography of southern elephant seal (Mirounga leonina) weanlings. Journal of Zoo and Wildlife Medicine 30(4): 526-531.
The mean values for amplitude and duration of electrocardiogram intervals, cardiac rhythm, and mean frontal plane QRS-axis were measured in 18 free-living weanling southern elephant seals (Mirounga leonina) anesthetized with tiletamine-zolazepam. Animals were 30-50 days old and had been weaned about 3 wk earlier. All animals had a normal sinus rhythm. The mean P-wave duration per animal had a range of 0.06-0.09 sec, and mean PR interval and QT interval ranges were 0.08-0.12 sec and 0.25-0.26 sec, respectively. The amplitude of the R wave was 0.22 mV in a VR and 0.5 mV in DI. The electrical axis was between -60 and +30 in 13 of the weanlings. Electrocardiograms were also obtained from five anesthetized juveniles and one adult female. The electrical axis of juveniles was between 0 and 120 , whereas the QRS vector for the adult female had an orientation of -150 . This report is the first detailed description of the southern elephant seal electrocardiogram.
Falabella, V., M. Lewis and C. Campagna (1999). Development of cardiorespiratory patterns associated with terrestrial apneas in free-ranging southern elephant seals. Physiological and Biochemical Zoology 72(1): 64-70.
Elephant seals resting on land show an irregular breathing pattern that combines periods of eupnea and apnea. In this article we describe ontogenetic changes in the breathing pattern and in the associated cardiac response in resting pups and weanlings of the southern elephant seal, Mirounga leonina. Apnea duration and the percentage of time spent in apnea were positively correlated with age: mean apnea length was greater in weanlings than in pups, with weanlings holding their breath for up to 8.7 min. Apnea length was not correlated with the duration of preceding or subsequent eupneas. The heart rate of pups and weanlings on land followed the pattern of bradycardia during apnea and tachycardia during eupnea. Young weanlings had a significantly smaller decrease in heart rate during apnea than older weanlings (28% vs. 36%). The instantaneous heart rate response to breathing changed from a variable to a regular pattern. These results suggest that the control processes that modulate the physiological cardiorespiratory changes necessary for diving start to develop on land during the first 11 wk of life.
Favero, M. (1996). Foraging ecology of pale-faced sheathbills in colonies of southern elephant seals at King George Island, Antarctica. Journal of Field Ornithology 67(2): 292-299.
The Pale-faced Sheathbill (Chionis alba) is an opportunistic predator-scavenger. During spring in Antarctica it foraged in colonies of southern elephant seals, obtaining placentas, pup carcasses, milk from nursing cows, blood, and feces. Afterbirths and pup carcasses constituted the bulk of the food consumed. Daily consumption estimates averaged 67 g/bird for placenta and 11 g/bird for pup carcasses, which are 54% and 26% of daily energy, requirements, respectively. Sheathbills spent 86% of the day foraging or displaying and 14% resting or preening. Actively feeding birds spent 38% of the time searching for food, 20% feeding, 23% resting, 14% on comfort activities, and 3% in agonistic behaviors.
Fayolle, C., C. Leray, P. Ohlmann, G. Gutbier, J.-P. Cazenave, C. Gachet and R. Groscolas (2000). Lipid composition of blood platelets and erythrocytes of southern elephant seal (Mirounga leonina) and antarctic fur seal (Arctocephalus gazella). Comparative Biochemistry and Physiology B Biochemistry & Molecular Biology 126B(1): 39-47.
Fedak, M. A. and B. J. McConnell (1993). Observing seals by satellite. NERC news 25: 26-28.
The article describes the open ocean behavior of southern elephant seals (Mirounga leonina), their long distance travel and diving, in relation to physical and biological aspects of the oceanic environment.
Fedak, M. A., T. A. Arnbom, B. J. McConnell, C. Chambers, I. L. Boyd, J. Harwood and T. S. McCann (1994). Expenditure, investment, and acquisition of energy in southern elephant seals. Elephant seals. Population ecology, behavior and physiology. B. J. L. Boeuf and R. M. Laws. Berkeley (CA), University of California Press: 354-373.
Information on the expenditure and investment of energy in southern elephant seals, Mirounga leonina, was collected during breeding and molt over four field seasons at South Georgia. Weight and body composition changes of mothers, pups, and breeding males were monitored during the breeding season. These changes were also measured in adult females, before and after the 70-day period when animals fed at sea between breeding and molt. During this period, information on foraging movements and behavior was gathered using purpose-built satellite-relay data loggers. Body composition changes were measured using isotope dilution techniques.
Breeding energetics information is discussed in relation to the evidence for differential investment in male and female pups. Large females produce larger pups, both at birth and weaning. Male pups are born larger than female pups. However, there is no evidence that mothers invest more energy (either relative or absolute) in male pups after birth once female size and birth weight are taken into account.
Foraging movements and diving behavior are discussed in terms of the oceanography of the foraging area and possible constraints placed by prey consumption on the seals' dive behavior. We suggest that the long distance travel of females to distant feeding locations may be advantageous in providing for the requirements for reliable fi)od sources in a long-lived, uniparous mammal. Dive characteristics changed during the different phases of activity in foraging animals in relation to the average daily velocity of the animal, water depth, and undersea topography.
Fedak, M. A., T. Arnbom and I. L. Boyd (1996). The relationship between the size of southern elephant seal mothers, the growth of their pups, and the use of maternal energy, fat, and protein during lactation. Physiological Zoology 69(4): 887-911.
Pregnant female southern elephant seals vary in size by more than a factor of three when they come ashore to give birth and nurse their pups. Pups are fed exclusively from the mother's body reserves, which vary in proportion to her mass at parturition. We measured the use of body materials and energy over the course of lactation using a combination of isotope dilution and mass change during four breeding seasons on South Georgia. On average, mothers lost 35% of their mass at parturition during lactation. This included approximately 52% of the energy, 61% of the fat, and 24% of the protein in the mother's body. The relative amount that mothers expend on their pups is highly variable and shows little consistent trend with the mother's mass. Some large mothers used approximately 30% of their stored energy (comprising around 40% of stored fat and 20% of body protein) to produce medium- or large-sized pups. Whereas some smaller mothers produced only small pups, others used all of or more than the reserves estimated to be available without incurring deleterious effects (68% of energy, 80% of fat, and 27% of protein). These small animals may be at risk of compromising their future reproduction. The production of small pups by these smaller females ma3' reflect a compromise between the survival of the pup and the future success of the mother. While we expected that the largest females might show a reduced efficiency, of mass transfer during lactation (because of high metabolic overheads), their ability, to reduce the duration of lactation seems to compensate for this, and no such reduction could be shown.
Fedak, M. A., N. J. McConnell, D. J. Slip, M. A. Hindell and P. J. B. Reijnders, H.R. (1998). Close encountersof the four kinds: movement patterns of recently weaned elephant seal pups from Macquarie Island. World Marine Mammal Science Conference Monaco, Lawrence, KS, Society for Marine Mammalogy.
Phocid seal pups use the energy provided by their mothers to stay alive until they find food. The amount they need is determined in part by the time it takes them to locate prey. How do they locate suitable foraging areas? There is no obvious way parents can direct pups to foraging areas but such information could reduce the demands placed on the mother. Using purpose built data logger/transmitters and the Argos system, we followed naive weaned elephant seal pups after they departed Macquarie Island, in December 1995 and 1996, for periods up to 6 months until some of them returned to Macquarie or other islands. Pups moved long distances after leaving the island. However, the tracks did not apparently radiate randomly in all directions. Some of the animals (18 of 28) travelled to the east and south forming a broad band of tracks which took them to locations over the southern end of the Pacific-Antarctic Ridge. Another group travelled out to the Southwest to areas over the Mid-Indian Rise. Some of the locations which they visited coincided with those used by adults or other pups from Macquarie in the same or previous seasons. The directed nature of the outward movements and the fact that some pups returned to Macquarie by direct routes suggest well developed navigational skills. Other encounters and coincidences are even more intriguing. Some pups followed the same tracks as others but were always separated in time, by several days. At other times, animals repeatedly arrived at the same position in the open sea but got there by different paths. Some pups moved in an apparently directed way to distant, isolated islands to which they had never been before. These observations suggest that specific information which shapes the pup's movements might be obtained after they leave the beach, either as communication from conspecifics or other sources. As yet, we have little idea of what 'these sources might be are or how they are used. But their existence may have important consequences for both reproductive strategies and the effects on the population of environmental variation.
Field, I., M. Hindell, D. Slip and K. Michael (2001). Foraging strategies of southern elephant seals (Mirounga leonina) in relation to frontal zones and water masses. Antarctic Science 13(4): 371-379.
Geolocating-time-depth-temperature-recorders (GLTDTR) provided a continuous record of diving behaviour in relation to water temperature for ten female southern elephant seals from Macquarie Island during their post-breeding trips to sea. Four water bodies were determined from depth/temperature profiles recorded by the GLTDTRs. These water bodies corresponded to Sub-Antarctic Mode Water (SAMW), Polar Front Zone Water (PFZW), Polar Front Water (PFW) and Antarctic Water Masses (AWM). Thermal structures within these water bodies did not influence seal diving behaviour. Overall mean dive depth, nocturnal dive depths, diurnal dive depths and dive duration were similar in all areas. However, individuals did change behaviour as they moved between different water bodies. Seals also used different water bodies in the two different years of the study. We suggest that variations in foraging behaviour among seals are a result of prey distribution associated with local oceanographic conditions, but also reflect important individual foraging strategies within thermal zones.
Field, I. C., C. J. Bradshaw, C. R. McMahon, J. Harrington and H. R. Burton (2002). Effects of age, size and condition of elephant seals (Mirounga leonina) on their intravenous anaesthesia with tiletamine and zolazepam. Vet Rec 151(8): 235-40.
Southern elephant seals (Mirounga leonina) were caught as part of a long-term demographic study on Macquarie Island. Over 18 months, 1033 seals were caught by hand and anaesthetised intravenously with a 1:1 mixture of tiletamine and zolazepam. Assessments were made of the effects of variations in the body condition and age at capture of the seals on the characteristics of their anaesthesia, including induction time and weighted recovery time. The size and condition of the seals were assessed by morphometric and ultrasound measurements. Weighted recovery times decreased as the body condition and age of the seals increased, but there were no residual effects of sex. There were no fatalities, and no periods of apnoea longer than five minutes were recorded. In individual seals there was a significant increase in weighted recovery time with successive captures.
Fletcher, S., B. J. Le Boeuf, D. P. Costa, P. L. Tyack and S. B. Blackwell (1996). Onboard acoustic recording from diving northern elephant seals. J. Acoust. Soc. America 100(4 Part 1): 2531-2539.
This study was the first phase in a long-term investigation of the importance of low-frequency sound in the aquatic life of northern elephant seals, Mirounga angustirostris. By attaching acoustic recording packages to the backs of six translocated juveniles, the aim was to determine the predominant frequencies and sound levels impinging on them, and whether they actively vocalize underwater on their return to their rookery at Ano Nuevo, California, from deep water in Monterey Bay. All packages contained a Sony digital audio tape recorder encased in an aluminum housing with an external hydrophone. Flow noise was minimized by potting the hydrophone in resin to the housing and orienting it posteriorly. The diving pattern of four seals was recorded with a separate time-depth recorder or a time-depth-velocity recorder. Good acoustic records were obtained from three seals. Flow noise was positively correlated with swim speed, but not so high as to mask most low-frequency sounds in the environment. Dominant frequencies of noise impinging on the seals were in the range 20-200 Hz. Transient signals recorded from the seals included snapping shrimp, cetacean vocalizations, boat noise, small explosive charges, and seal swim strokes, but no seal vocalizations were detected. During quiet intervals at the surface between dives, the acoustic record was dominated by respiration and signals that appeared to be heartbeats. This study demonstrates the feasibility of recording sounds from instruments attached to free-ranging seals, and in doing so, studying their behavioral and physiological response to fluctuations in ambient sounds.
Follis, M. and F. J. Mortenson (1995). Northern elephant seal (Mirounga angustirostris) mounting of harbor seals (Phoca vitulina) pups. World Marine Mammal Science Conference Orlando, Florida, Lawrence, KS, Society for Marine Mammalogy.
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Gales, N. J. and H. R. Burton (1987). Prolonged and multiple immobilizations of the southern elephant seal using ketamine hydrochloride-xylazine hydrochloride or ketamine hydrochloride-diazepam combinations.
Gales, N. J. and H. R. Burton (1987 a). Ultrasonic measurement of blubber thickness of the southern elephant seal, Mirounga leonina (Linn.). Australian Journal of Zoology 35(3): 207-217.
Ultrasound measurements of subcutaneous fat at 18 body sites on each of 23 southern elephant seals Mirounga leonina , together with circumference and length measurements, were used to estimate the total subcutaneous blubber weight on each animal. Twelve cows (including animals that were pregnant and others at early, mid-, late and post-lactation), 10 males and one male pup were anaesthetised for these measurements, made at Heard I. (53 degree 01'S.,73 degree 23'E.) on various dates in October and November 1985. Comparison of the estimates of blubber weight from cows at various stages of lactation allowed a mean blubber loss of 62 multiplied by 8 kg per cow per lactation to be calculated. It is suggested that measuring variations in the subcutaneous fat reserves of cows coming ashore to pup at Heard I. may be one relevant approach in any future research that attempts to explain the 60% drop in pup production at that island between 1949 and 1985. The use of ultrasound to estimate the subcutaneous fat reserves of seals was shown to be a safe, non-invasive and logistically practical technique.
Gales, N. J. and H. R. Burton (1987 b). Prolonged and multiple immobilizations of the southern elephant seal using ketamine hydrochloride-xylazine hydrochloride or ketamine hydrochloride-diazepam combinations. J. Wildl. Dis. 23(4): 614-618.
Thirty seven southern elephant seals (Mirounga leonina) were singularly or repeatedly immobilized with combinations of ketamine hydrochloride (HCl) and xylazine HCl or ketamine HCl and diazepam. Atropine sulphate was included in the drug combinations. To permit experimental procedures the seals were immobilized for periods of 30-330 min. The mean induction dose of ketamine HCl was 8.71 +/- 0.25 mg/kg (mean +/- SE). The mean induction time was 16.02 +/- 2.62 min. For the elephant seals immobilized for periods in excess of 180 min, the mean dose of ketamine HCl used per hr was 3.31 +/- 0.13 mg/kg/hr and the mean dose of ketamine HCl used per hr postinduction was 1.31 +/- 0.15 mg/kg/hr. The mean dose of diazepam used was 0.09 +/- 0.01 mg/kg and the mean dose of xylazine HCl was 0.41 +/- 0.01 mg/kg. Elephant seals were weighed on 20 occasions (weight range: 897-1,932 kg) and the relationship between standard length and weight was found to be: Weight = 9.98 length - 2,317.63 (r2 = 0.724). Adverse reactions to seals immobilized only once or twice were not observed. Two seals immobilized on three occasions developed abscesses at the site of injection.
Gales, N. J., M. Adams and H. R. Burton (1989). Genetic relatedness of two populations of the Southern elephant seal, Mirounga leonina. Marine Mammal Science 5(1): 57-67.
Blood samples from southern elephant seals (Miroungu leonina) from Heard and Macquarie Islands were surveyed electrophoretically for protein variation. Thirty proteins encoded by a minimum of 35 loci were saeened, four of which were found to be polymorphic. Statistically significant differences in allele fre- quencies were found between the two populations at three loci. Heterozygosity estimates for the Heard and Macquarie island populations were 0.034 ± 0.020 (mean ± standard error) and O.029 ± 0.017 respectively, with a Nei distance of 0.007. The findings suggest that the two populations may have diverged genetically and very limited gene flow exists between the islands, a finding consistent with limited information from mark-recapture studies.
Key words: southern elephant seals, Mirounga leonina, population structure, electrophoresis, genetic variation, blood proteins, genetic relatedness.
Gales, N. J. and H. R. Burton (1989). The past and present status of the southern elephant seal (Mirounga leonina L.) in Greater Antarctica. Mammalia 53(1): 35-47.
Counts of southern elephant seals at the Vestfold Hills from 1958 to the present reveal that the population has declined by half to two thirds. The decline of this predominantly male, moulting population is similar to reported declines of breeding populations of elephant seals in the Kerguelen province. The population of moulting seals at the Windmill Islands is larger than previously thought and its status is unknown. The Vestfold Hills' and Windmill Islands' populations are the only known aggregations of southern elephant seals in Greater Antarctica. The accessibility of suitable areas on the Antarctic coast for moulting during summer is shown to be the reason for selection of these sites.
Gales, N. (2000). A field review of the Macquarie Island elephant seal hot iron branding program: December 2000., Antarctic Animal Ethics Committee.
Galimberti, F. (1995). Competizione tra i maschi e selezione sessuale nell' elefante marino del sud (Mirounga leonina) della Penisola di Valdés [Intermale competition and sexual selection in southern elephant seals (Mirounga leonina) of the Valdés Peninsula; in Italian, with English abstract]. Roma, Università degli Studi di Roma "La Sapienza".
The target of my research project was sexual selection by inter-male competition in southern elephant seals (Mirounga leonina) of the Valdes Peninsula (Patagonia, Argentina). I measured various male phenotypic traits, including size, morphology, tenure, behavioural performance. Moreover, I measured the three main components of male individual fitness, i.e., female holding, mating success, and number of females fertilized. I calculated selection pressures using different univariate and multivariate methods, including non-parametric fitness functions, selection differentials and gradients, and path-analysis. At the same time, I studied the structural relationship between male traits, with particular attention to behavioural ones. Structural components of phenotype (age, linear size, weight) were not under any direct selection pressure. On the contrary, they are under indirect pressures due to their effect on behavioural traits, that are the direct target of sexual selection in this population. Secondary sexual traits, including all the components of the proboscis, had small and non significant selection gradients. On the contrary, various measures of behavioural performance in competition, including a cardinal dominance measured at population level, were under strong directional selection. Competition success is determined in part by structural size and in part by basic measures of behavioural activity (interaction rate, aggressiveness), but some of its variance was not explained by the male traits I was able to measure. Male experience may have a significant role in competition among mature males, explaining this residual variance in competition success. The large variation of the local breeding condition (female density, harem size, number of males) seems to have only a slight effect of selection pressures. In the Valdes Peninsula population, deterministic factors seem to effectively determine intra-selection pressures, with the variation in male phenotype explaining the majority of the variation in competition and breeding success.
Galimberti, F. and L. Boitani (1999). Demography and breeding biology of a small, localized population of southern elephant seals (Mirounga leonina). Marine Mammal Science 15(1): 159-178.
Southern elephant seals have been studied in depth in most of their breeding range. One notable exception is the Falklands Islands population. We present data on demography and breeding biology of elephant seals of Sea Lion Island, the main breeding site of this species in the Falklands. Sea Lion Island shelters a small, localized population of southern elephant seals (516 breeding females in 1995 and 518 in 1996). Comparison with the few available census data collected prior to our study suggests that the population has been stable in the short term (1989-1996). Females produced pups at maximum rate and pup mortality was low (2.13%). Breeding sex ratio was strongly unbalanced, with about 14 females per breeding male and 47 females per harem-holding males at peak haul-out. Survival rate between breeding seasons was very similar to that recorded in other populations and was in accordance with clinical variation with latitude. Sex ratio at birth was balanced, and no significant weight dimorphisms at weaning between sexes was detected (males: 135.4 kg; females: 132.0 kg). Weaning weight was correlated with size class of the mother.
Galimberti, F., S. Sanvito and L. Boitani (2000). Marking of southern elephant seals with passive integrated transponders. Marine Mammal Science 16(2): 500-504.
In 1995 we started a long-term research project on southern elephant seals (Mirounga leonina) at Sea Lion Island, Falkland Islands. In 1997 we implanted Trovan PIT tag (model ID 100, Trovan Inc.; http://www.trovan.com/) transponders in 510 weanlings (= 93.2% of the full cohort of survivors). These small glass-encapsulated transponders (length 11.5 mm, diameter 2.15 mm, weight 0.1 g), operating at 128 KHz, are widely used in zoos and are endorsed by the Captive Breeding Specialist Group of the IUCN (Wright et al. 1998). We chose Trovan Inc. because they supplied a hand-held reader (model LID 500) that, although large (length 22 cm, width 17.5 cm, height 27 cm) and awkwardly shaped, had the greatest scanning distance (18-20 cm, depending on battery charge) of the models available on the market. The reliability of PITs in the long term remains unclear, but preliminary evidence reported in the literature (Wright et al. 1998) indicates that, if the transponder is properly placed, it should remain in that particular position without migration into deeper tissues. PIT tagging has many advantages, but it is expensive (6-12 times the cost of a plastic tag), marked individuals are not easily recognized at first encounter, and reading of the ID code requires an awkward battery-operated device. Hence, we consider PITs not as a replacement for plastic tags but as an effective back-up system, especially when lifetime identification is required. In this role, PITs are an effective way to mark elephant seals and probably seals in general.
Galimberti, F., L. Boitani and I. Marzetti (2000 a). The frequency and costs of harassment in southern elephant seals. Ethology Ecology & Evolution 12(4): 345-365.
Notwithstanding the important role of male harassment of females for theories of the evolution of mating systems, accurate estimates of its frequency and costs are available for only a few species. In this paper, we quantify the frequency of harassment in southern elephant seals, compare occurrences of harassment inside and outside harems, and estimate the costs of harassment in two populations at Sea Lion Island (Falkland Islands) and Punta Delgada (Valdés Peninsula). Southern elephant seal males are much larger than females, have enlarged canines, and are much more agile on land; hence, females have a small probability of escape from approaching males and may suffer intense molestation. Most males had limited access to females due to the despotic mating system, and their libido was high. Females were approached by males at high frequency, mostly when out of oestrus. The harassment level was negatively related to the ratio of breeding females to breeding males, and females breeding at the peak of the season suffered a lower level of harassment. Females of large harems were harassed less, and their likelihood to interact with secondary males was lower. The activity of harem females was less disrupted, and females in large harems had an higher proportion of resting time. Isolated females suffered more herding episodes, and were approached more frequently by secondary males. The main short-term cost of harassment was disruption of the females’ activity schedule; harassment level and total active time were positively related. Suckling bouts were rarely interrupted by male harassment. Mother and pup separations caused by males interaction were rare, short-lasting, and rarely permanent. There was little effect of harassment on weanling weight, physical damage of females was rare, and there was only a slight non-significant negative relationship between harassment level during one season and the likelihood of surviving to the next.
Galimberti, F., L. Boitani and I. Marzetti (2000 b). Female strategies of harassment reduction in southern elephant seals. Ethology Ecology & Evolution 12(4): 367-388.
Female southern elephant seals are expected to adopt behaviours that reduce the costs of male harassment. We studied thestrategies and tactics of harassment reduction in two populations, at Punta Delgada (Valdés Peninsula, Argentina) and at Sea Lion Island (Falkland Islands) during five breeding seasons in all. Females synchronized their breeding activities to reduce harassment risk, and rarely bred alone to reduce the likelihood of encounters with subadult males. Females showed a clear preference for larger harems, that guaranteed a reduced harassment risk: movements between arrival on land and parturition were mostly from smaller to larger harems, and the likelihood of abandonment was lower for large harems. Females protested against approaching males in the vast majority of interactions, regardless of the social context and the status of the interacting male, but protest varied with female breeding status and male phenotype. Frequency of protest of individual females decreased linearly from the beginning of oestrus to departure to sea. Interactions with mature males were less protested. The frequency of protest linearly decreased with increase in age class, and mating attempts by males of higher status and dominance rank were less often protested. Most of this variation with male phenotype, however, was due to the higher probability of older and more dominant males to interact with oestrus females that had an intrinsicly lower tendency to protest. Protest variation in relation to male phenotype was more parsimoniously explained as a consequence of differential access of males to oestrus females rather than of female selectivity. Protests had a role in disruption of mating attempts, although the phenotype of interactors was more important: adult, large and dominant males disrupted interactions regardless of incitation by female protest.
Galimberti, F., L. Boitani and I. Marzetti (2000 c). Harassment during arrival to land and departure to sea in southern elephant seals. Ethology Ecology & Evolution 12(4): 389-404.
During the breeding season female elephant seals spent most of their time on land inside harems. When they arrive on land before joining harems, and when they leave harems to return to sea, they are exposed to secondary males and may suffer intense harassment. Hence, arrival and departure present an ideal opportunity to test hypotheses concerning female tactics of harassment reduction. We studied harassment during arrival and departure in two southern elephant seal populations at Punta Delgada (Valdés Peninsula; DEL hereafter) and Sea Lion Island (Falkland Islands; SLI hereafter). Females were less likely to be intercepted by males during arrival than during departure. They also arrived mostly at high tide, thereby reducing the distance from water to the harems. Interception rate and harassment during departure were higher at DEL, where male density and the breeding sex ratio affected the likelihood of interception; on SLI, the socionomy had a small effect. Harassment was higher at low tide at DEL but not at SLI, because tide level variation was larger at DEL and this resulted in a larger variation in the distances of the harems from the water. Females departed more often than expected at high tide at DEL but not at SLI. In both populations females departed directly to sea, rarely stopping before reaching the water, and they never sought contact with males. Social distraction during departure significantly reduced the likelihood of interception. Departures were more frequent during periods of high social activity, and females departing just after other females were less prone to harassment. Accepting copulations with secondary males may reduce the dangerous effects of harassment: interactions occurring during departure were less frequently protested, but we found no indication that departing females were facilitating copulations in a special manner. Quantity and quality of protest during departures was similar to protest during the last days of residence of the females in the harem.
Galimberti, F. and S. Sanvito (2001). Modelling females haul out in southern elephant seals (Mirounga leonina). Aquatic Mammals 27(2): 92-104.
In Pinnipedia species is difficult to achieve good estimates of population size by direct counts, because a part of the population is at sea at any time. In southern elephant seals (Mirounga leonina) the estimation of population size is carried out starting with the number of females hauled out during the breeding season, by applying a correction factor calculated from life tables. Different models were proposed in the literature to estimate the total number of females hauled out. In this paper, we consider the model proposed by Rothery & McCann (1987) for the South Georgia population, applying it to a five years data set for the population of Sea Lion Island (Falkland Islands). We test the assumptions of the model, finding them reasonable. We fit the model to our data set, obtaining an excellent fit in all cases, better than or equal to other models proposed in the literature. The precision of the estimation depended mostly on the length of presence on land of females, which is a constant of the model. A 1 day variation in length produced a 4% variation in the estimated total number of females. When a good model of the haul out process is already available for the population, even a single count close to the peak of the season is enough to estimate total females in the ± 2% range. When such a model is to be estimated from data, at least 8 counts are needed to have a good estimate. The model was not only a good description of the haul out process at population level, but its application to a set of daily counts of single harems demonstrated its usefulness also at sub-population level.
Galimberti, F., S. Sanvito, L. Boitani and A. Fabiani (2001). Viability of the southern elephant seal population of the Falkland Islands. Animal Conservation 4: 81-88.
Accurate long-term series of demographic data are available for most populations of southern elephant seals. However, research on elephant seals of the Falkland Islands began only recently, and information for an accurate forecasting of the future of this population is lacking. In this paper, we present data on the current status and of the population and its trend in size during the last 11 years. We built an age-structured model of the population and analyzed the effect of variation in demographic parameters on population growth. Elasticity analysis demonstrated that variation in mortality has a more pronounced effect on instantaneous growth rate than equivalent variation in fecundity. We examined the effects of environmental variability, inbreeding, and catastrophes on population viability by computer simulation using the VORTEX PVA program. In the stochastic model, the most important factor affecting extinction risk was variability in mortality rates, in particular of the adult classes. We concluded that, although the population does not appear to be at immediate risk of extinction, its small size and isolation make compelling an accurate monitoring of population trend and the acquisition of additional information on life history and feeding strategies.
Galimberti, F. (2002). Power analysis of population trends: an application to elephant seals of the Falklands. Marine Mammal Science 18: 557-566.
Galimberti, F., A. Gallastroni and S. Sanvito (2002). Behavioural and morphometric measurements of parental investment in southern elephant seals at the Falkland Islands. Polar Biology 25: 399-403.
Parental investment is a key variable in the study of breeding strategies and life-histories evolution. In Pinnipedia, parental investment is usually calculated from direct measurements of pup weight gain or energy transfer between the mother and the pup. These direct methods always involve handling and restraining procedures that pose practical, logistical and ethical problems. To evaluate if weighing can be substituted by indirect observational estimates of parental investment, we analysed the relationship among various behavioural measures of suckling and post-natal growth in the southern elephant seal population of Sea Lion Island (Falkland Islands). Behavioural measures were in all cases a poor predictor of true investment as estimated by weighing. We concluded that there are currently no e.ective alternatives to direct handling, and that the best way to reduce the potential adverse impact of investment studies is the improvement of the handling protocol, which should include an estimation of the long-term e.ects on the health of handled animals. Further research is needed to test the validity of non-behavioural indirect methods (e.g. 3D photogrammetry).
Galimberti, F., A. Fabiani and S. Sanvito (2002 a). Opportunity for selection in southern elephant seals (Mirounga leonina): the effect of spatial scale of analysis. Journal of Zoology London 256: 93-97.
The opportunity for selection, I, calculated as the variance in relative fitness, sets an upper limit to the amount of adaptive change that selection may produce. Therefore, it is a potentially valuable, and frequently used, measure of the potential of action of phenotypic selection. Although many different aspects of I calculation and analysis have been explored, the effect of the spatial scale chosen for calculation received little attention, notwithstanding the growing evidence that natural populations are not homogeneous and present a hierarchical spatial structure. The effect of scale on the estimation of I was examined from data collected in two populations of southern elephant seals (Mirounga leonina), an easily observable and strongly polygynous species. A significant effect of spatial scale on three important aspects of I calculation and analysis was found: dependence of I on mean fitness, between population variation of I, and effect of local demography on I.
Galimberti, F., A. Fabiani and S. Sanvito (2002 b). Measures of breeding inequality: a case study in southern elephant seals. Canadian Journal of Zoology 80: 1240-1249.
Inequality in distribution of resources is a key aspect of evolutionary biology, in particular in relation to distribution of mates an copulations. Notwithstanding its important role, inequality is not easily defined, and its measurement is complicated by theoretical and methodological issues. Although the formal treatment of inequality has been mostly limited to the evolution of lek mating system, a methodologically correct approach to measurement of inequality has a general validity for the study of any kind of mating system. In this paper, we analyze inequality in a large set of southern elephant seals harems. The observed distribution of fertilizations was significantly different from both the expected distribution with equal shares of resources, and the expected distribution with equal propensities to get resources. We calculate and compare various measures of inequality, observing a wide variation, in particular among unbounded and bounded indices. We check the effect of choosing a specific measure of inequality by considering the effect of two aspects of harem socionomy, the number of females in the harem (i.e., the total amount of resources to be shared) and the number of males associated to the harem (i.e., the number of competitors). The choice of a specific measure of inequality had a strong impact on the results obtained, and should be considered a critical step in every study of functional and evolutionary correlates of inequality. Not bounded indices showed a strong relationship with both harem size and number of males, while no effect was evident in the analysis of bounded indices. This demonstrates that, in this species, the despotism of the mating system remains high even in large harems and with many competitors, i.e., with the worst conditions for monopolization.
Galimberti, F., A. Fabiani and L. Boitani (2003). Socio-spatial levels in linearity analysis of dominance hierarchies: a case study on elephant seals. Journal of Ethology 21: 131-136.
The analysis of linearity is a key aspect of the study of dominance hierarchies. To study the effect of the choice of socio-spatial level of analysis, we calculated linearity in a large set of southern elephant seal (Mirounga leonina) hierarchies from two populations (Valdés Peninsula and Falkland Islands). The socio-spatial level of analysis affect the observational effort, the completeness of matrices, and the frequency of unknown relationships. These factors, in turn, have a notable effect on linearity. We conclude that dominance should be studied at local level, where the absence of structural zeros, and the low incidence of observational zeros, produce complete matrices, well rooted in the true spatial and social structure of the population. Depending on the specific social system, the extrapolation of dominance from the local level to higher levels may result in sparse matrices, and in biased estimates of linearity. The variation of the socio-spatial level of analysis may in part explain the contrasting results obtained in different studies of linearity of dominance hierarchies.
Garcia-Aguilar, M. C. (2004). Breeding biology of the northern elephant seal (Mirounga angustirostris) at the Isla San Benito del Oeste, Eastern Pacific, Mexico. Aquatic Mammals 30(2): 285-295.
Garza, J. C. (1998). Population genetics of the Northern elephant seal. Dapartment of Biology. Berkeley, California, University of California.
Gibbney, L. F. (1957). The seasonal reproductive cycle of the female elephant seal (Mirounga leonina, Linn.) at Heard Island.
Goldstein, T., S. P. Johnson, L. J. Werner, S. Nolan and B. A. Hilliard (1998). Causes of erroneous white blood cell counts and differentials in clinically healthy young northern elephant seals (Mirounga angustirostris). Journal of Zoo and Wildlife Medicine 29(4): 408-412.
From 1993 to 1995, approximately 10% of the clinically healthy northern elephant seals (Mirounga angustirostris) at The Marine Mammal Center in California exhibited a large unexplained increase in their white blood cell (WBC) count. In these animals, WBC counts ranged from 28,780 to 125,000/mm3, with a mean of 50,087 /mm3. Significant correlations between the leukocytosis and weight gain and day of admittance were identified, but no correlation existed between leukocytosis and general state of health, sex, length of stay, or diet. Bone marrow contamination of blood samples, erroneous automated leukocyte counts, and leukogram changes consistent with subclinical inflammation were the major factors contributing to the elevated WBC counts in these apparently clinically healthy animals.
Goldstein, T., S. P. Johnson, A. V. Phillips, K. D. Hanni, D. A. Fauquier and F. M. D. Gulland (1999). Human-related injuries observed in live stranded pinnipeds along the central California coast 1986-1998. Aquatic Mammals 25(1): 43-51.
From January 1986 to September 1998, of a total of 6196 live stranded pinnipeds including California sea lions (Zalophus californianus), Pacific harbor seals (Phoca vitulina), northern elephant seals (Mirounga angustirostris), northern fur seals (Callorhinus ursinus), Guadalupe fur seals (Arctocephalus townsendi) and Steller sea lions (Eumetopias jubatus) admitted to a rehabilitation center on the central California coast, 464 (7.5%) had human-related injuries. Three hundred and six (5%) had lesions caused by gunshots, 107 (1.7%) had lesions caused by entanglement with manmade marine debris (includes active or discarded fishing nets and monofilament line, packing straps, plastic bags, rope and rubber o-rings), 46 (0.7%) had injuries caused by fishing tackle and 5 (0.1%) had boat propeller damage. The majority of human-interaction injuries seen in these pinnipeds involved yearling California sea lions that stranded in Monterey Bay. June was the peak month for admission of animals with these injuries. Wounds caused by gunshots most commonly occurred in California sea lions. The most effective way of diagnosing gunshot cases was by radiography.
Goldsworthy, S. D., X. He, G. N. Tuck, M. Lewis and R. Williams (2001). Trophic interactions between the Patagonian toothfish, its fishery, and seals and seabirds around Macquarie Island. Marine Ecology Progress Series 218: 283-302.
Green, K. and R. Williams (1986). Observations on food remains in faeces of elephant, leopard and crabeater seals. Polar Biology 6( 1): 43- 45.
Faecal material of leopard (Hydrurga leptonyx ), crabeater (Lobodon carcinophagus ) and elephant (Mirounga leonina ) seals was collected from the vicinity of Davis station, Antarctica. Very few identifiable remains were found in elephant seal droppings. Fish remains, mainly of Pleuragramma antarcticum , were found in both leopard and crabeater seal droppings. The mysid Antarctomysis maxima was also found in crabeater seal droppings and amphipods and decapod crustaceans in leopard seal droppings.
Green, K. and H. R. Burton (1993). Comparison of the stomach contents of southern elephant seals, Mirounga leonina, at Macquarie and Heard Islands. Marine Mammal Science 9(1): 10-22.
There are three major breeding populations of southern elephant seals centered on Macquarie Island, Kerguelen-Heard Islands and South Georgia-Antarctic Peninsula. The composition of the diet differs between these populations based on published data from Signy Island and data presented here from Macquarie and Heard Islands. These differences in diet appear to be linked to the location at which seals were sampled ranging from the least Antarctic (Macquarie Island) to the most Antarctic (Signy Island). The major food remains consisted of cephalopod beaks and fish eye lenses. More benthic material was found at Heard Island than at Macquarie Island. The diet at Macquarie Island differed between summer and winter and between young animals and adults. The difficulty in collecting dietary samples of southern elephant seals near their main foraging areas makes the study of the feeding ecology of this species extremely difficult in comparison with other Southern Ocean species.
Green, K. (1995). Difficulties in assessing population status of ice seals. Wildlife research 22(2): 193-199.
The best method of monitoring ice seal populations in shifting pack ice is by aerial census. However, there are a number of problems with this method that are difficult to address in the pack ice, being best addressed on more accessible ice seals such as the Weddell seal. Counts made during the moult are affected by the fact that Weddell seals can leave the fast ice to forage. Seal numbers on the fast ice will therefore differ depending upon the proximity and availability of prey species, with lower numbers being recorded on the fast ice the further the seal has to travel from the ice to find food. In any census the subgroup of the population that is being counted must be known. Southern elephant seals and Weddell seals haul out to moult in sequences on the basis of age, sex and reproductive condition. This leads to periods of high and low counts through the moult. Examination of data on crabeater seals indicates that a putative 60% decline in numbers may have been due to counts being made at different times of the moult and therefore with different subgroups of the population being counted.
Green, K., D. J. Slip and G. J. Moore (1998). The take of fish species by seabirds and marine mammals in the Australian Fisheries Zone around Heard Island: the potential for competition with a commercial fishery. Polar Biology 20(4): 273-280.
The number of predators from Heard Island foraging in shelf waters, their prey requirements, and the proportion of their diet that was commercial and noncommercial fish were estimated. The calculated annual consumption of commercial fish species varied between 36,360 and 84,166 tonnes. The non-commercial Krefftichthys anderssoni was the preferred prey for most predators, and when its occurrence in diets was low it was replaced by crustaceans and commercial fish species. The estimated annual consumption of Champsocephalus gunnari was approximately 2 and 6 times the highest and lowest estimates respectively of the biomass of this species, obtained from three fisheries research cruises. For Dissostichus eleginoides, the maximum estimate was 28% of the highest estimate of biomass. The current fishery for D. eleginoides will most likely impact on southern elephant seals, whose population decreased by 50% between the 1950s and the 1980s, possibly as a result of overfishing around Iles Kerguelen.
Griffiths, D., R. F. Seamark and M. M. Bryden (1979). Summer and winter cycles in plasma melatonin levels in the elephant seal (Mirounga leonina). Australian Journal of Biological Sciences 32(6): 581-586.
Plasma melatonin concentration of immature male elephant seals was determined by radioimmuno-assay. Comparison of concentrations during two 24-hr periods, one in midsummer and one in midwinter, showed that there was a marked circadian cycle in winter which was greatly modified during the long day length of summer. It is suggested that in summer there was sufficient ambient lighting during the night hours to depress the nocturnal rise in plasma melatonin. The complexity of pineal cycles in the natural environment is stressed, and in this regard the polar regions are of particular interest due to the extreme seasonal changes in day length here.
Griffiths, D. J. (1980). The control of the annual reproductive cycle of male elephant seals (Mirounga leonina) at Macquarie Island. Brisbane, Queensland, Australia, University of Queensland.
Griffiths, D. J. (1984 a). The annual cycle of the epididymis of the elephant seal (Mirounga leonina) at Macquarie Island. Journal of Zoology London 203(2): 181-191.
Griffiths, D. J. (1984 b). The annual cycle of the testis of the elephant seal (Mirounga leonina) at Macquarie Island. Journal of Zoology London 203(2): 193-204.
The testis of the Southern elephant seal demonstrates obvious seasonal fluctuations in weight, with lowest value in mid-winter (May-June: 150-180 g/tonne body weight) and highest values during the breeding season (September-October: 350 g/tonne body weight). These weight changes are due to changes in the size of the seminiferous tubule, there being little seasonal change in the amount of stroma. The testosterone levels in the testis also fluctuate seasonally, rising in July and August before breeding begins, but falling away to baseline values before mid-breeding (October). Plasma testosterone is low throughout the year except for a single peak in September, the first month of breeding. While there is a seasonal cycle in Leydig cell size, it is not related to either plasma or testicular testosterone ccentration. Both testis weight and testosterone content fluctuations closely match an annual cycle in adenohypophyseal gonadotroph population previously described in the species (Griffith 1980).
Griffiths, D. J. (1985). Endocrine regulation of seasonal breeding in the male southern elephant seal (Mirounga leonina) at Macquarie Island. Studies of sea mammals in the South Latitudes. J. K. B. Ling, M.M. Sidney, South Austr. Museum: 31-40.
The testes of male elephant seals at Macquarie I. have been shown to be quiescent from Dec. to July inclusive. The first sperm were released from the seminiferous epithelium in Aug., but did not reach the tail of the epididymis until Sep. During Sep. and Oct. the seminiferous tubules remained fully active, but in Nov. there was a reduction in elongated spermatid (sperm) production and a loss of round spermatids into the lumen as the Sertoli cells regressed. The changing functional status of the testis coincided with histological changes in the pituitary gland. Pineal gland mass, relative to body weight, increased during the winter and fell during spring and summer in a cycle that was significantly correlated to day length. The high level of pineal gland activity during months of short day length suppresses pituitary gonadotrophic activity and reduces the gonadotroph population, which in turn leads to inactivation of the testes. As day length increases, pinealocytes decrease in size and activity, the gonadotroph population of the pituitary increases and the increasing gonadotrophin output initiates the onset of spermatogenesis.
Guinet, C. (1991). Growth from birth to weaning in the southern elephant seal (Mirounga leonina). Journal of Mammalogy 72(3): 617-620.
The population of elephant seals (Mirounga leonina ) in the southern Indian Ocean has decreased drastically over the past 4 decades. Several investigators have attempted to understand the reasons for this decline. Little et al. (1987) suggested that variations in birth weight and weaning weight could reflect changes in food resources. I weighed elephant seals from birth to weaning to test the hypothesis that differences in growth rates at this time could help to understand the rapid decline of the population of elephant seals on Crozet Island compared to the stable population on Kerguelen Island. In 1988, 56 pups were weighed just after birth on Crozet Island, and 29 pups were weighed on Kerguelen Island. Among the 56 pups from Crozet Island, 40 also were weighed just after weaning, as were 22 of the 29 on Kerguelen Island. In 1987 and 1988, pups were removed from harems established on sandy beaches of Baie Americaine on Crozet Island, and Anse du Pacha and Ratmanoff on Kerguelen Island. The sample means of the two breeding stocks were analyzed with Student's t-tests.
Guinet, C. (1992). Hunting behavior of killer whales (Orcinus orca) around the Crozet Islands. Canadian Journal of Zoology 70(9): 1656-1667.
Killer whales around the Crozet Is. consume a great variety of prey, including fish, penguins, elephant seals, and occasionally large cetacea. Predation techniques used on elephant seals and penguins, which are easily observed from the shore, are described. Hydrophones were used to record the acoustic behavior of the whales during their hunts for both types of prey. The successful predation of 29 elephant seals was observed, 24 of which were weaned pups. Seals were captured along the banks, near river outlets, by voluntary stranding of the whales on the beaches, or by attack on seals swimming in bays. Hunting techniques were routinely used in "strategic" points apparently chosen specifically according to location and climatic factors. King penguins were hunted along the banks, particularly where algae prevailed, or offshore. While hunting, whales tended to be very quiet and used acoustic signals sparingly, emitting a few isolated clicks and short-distance contact calls. Reactions of whales exposed to artificial sounds tended to show that they localize their prey by passive listening. When an elephant seal was captured, long distance contact calls characterized by excitement were emitted 72% of the time and resulted in the arrival, by "porpoising," of the most distant members of the group, along with whales of other groups coming from several km away. The author hypothesizes that the adaptive value of this behavior is to allow the size of the hunting unit to adjust itself to the size of the prey by permitting not only members of the same group to associate, but also members of other groups to associate temporarily.
Guinet, C. (1992). Croissance des éléphants de mer de l'archipel Crozet (46° 25' S, 51° 45' E) pendant leur première année de vie (in French with English summary). Mammalia 56(3): 459-468.
Growth of Mirounga leonina has been studied between birth and first year moult on Crozet Archipelago. During the 3 week lactation period weight increased from 38.5 kg at birth to 128.4 kg at weaning. The heaviest at birth grow the fastest. During the fasting period, the weight loss is positively correlated with the weaning weight. Average weight of elephant seals back for their first year moult was 184.5 kg. Assuming that the growth rate remains at the same level, sexual maturity of females could be reached at 2 years, which is confirmed by tag controls. Elephant seal growth does not appear to be depressed on the Crozet Archipelago, suggesting that factors other than food depletion probably explain the sharp decrease in size of the elephant seal population there.
Guinet, C. (1992). Comportement de chasse des orques (Orcinus orca) autour des iles Crozet. Canadian Journal of Zoology 70(9): 1656-1667.
Killer whales around Crozet Islands consume a great variety of preys, including fish, penguins (Eudyptes sp.), elephant seals (Mirounga leonina ), and, occasionally, large cetacea. Predation techniques used on elephant seals and penguins, which are easily observed from the shore, are described. The successful predation of 29 elephant seals was observed, 24 of which were weaned pups. Seals were captured along the banks (n = 3), near river outlets (n = 14), by voluntary stranding of the whales on the beaches (n = 7), or by attach of seals swimming in bays (n = 5). Hunting techniques were routinely used in "strategic" points apparently chosen specifically according to the location and climatic factors. King penguins were hunted along the banks (n = 13), particularly where algae prevailed, or offshore (n = 32). While hunting, whales tended to be very quiet and used acoustic signals sparingly, emitting a few isolated chicks and short distance contact calls. Reactions of whales exposed to artificial sounds tended to show that they localize their prey by passive listening.
Guinet, C. (1992). Croissance des elephants de mer de l'archipel Crozet (46[degree]25mnS, 51[degree]45mnE) pendant leur premiere annee de vie. Mammalia 56(3): 459-468.
Guinet, C. and P. Jouventin (1992). Hunting behaviour of killer whales on Crozet Archipelago. European Research on Cetaceans 6: 152-153.
Guinet, C., P. Jouventin and H. Weimerskirch (1992). Population changes, movements of southern elephant seals on Crozet and Kerguelen archipelagos in the last decades. Polar Biology 12(3-4): 349-356.
The elephant seal (Mirounga leonina) populations breeding on the Crozet and Kerguelen Archipelago were surveyed during the eighties. Elephant seals were observed moving between Kerguelen, Amsterdam, Heard Islands and Vestfold Hills and between Crozet and Prince-Edward Archipelagos. No exchanges were observed between Crozet and Kerguelen Archipelagos suggesting that the two populations are more isolated than previously stated. On the Crozet Archipelago, since 1966, the Possession Island population showed at 70% reduction in numbers of cows ashore and the population is still decreasing. On Kerguelen Island there has been a decline of 44% from 1956 to 1989 but the population appears to have stabilized since 1984. It is suggested that elephant seal populations in the Southern Indian Ocean may have been affected by a change at the trophic level over the last four decades. But the highest rate of decrease observed on the Crozet Archipelago and the fact that the population is still decreasing may be explained by additional factors, in particular by killer whale (Orcinus orca) predation.
Guinet, C. (1994). Poids a la naissance et croissance des elephants de mer austraux. Quelles informations nous apportent-ils sur le milieu marin? Recueil de Medecine Veterinaire de l'Ecole d'Alfort 170(2-3 Numero special): 105-110.
Guinet, C. and J. Bouvier (1995). Development of intentional stranding hunting techniques in killer whale (Orcinus orca) calves at Crozet Archipelago. Canadian Journal of Zoology 73( 1): 27- 33.
This paper describes the trend in the practice of what we interpret to be the "intentional stranding" hunting technique of two juvenile female killer whales (Orcinus orca), A4 and A5, belonging to pod A on the beaches of Possession Island, Crozet Archipelago. Pod A was composed of three adult females, A2, A3, A6 and one adult male, A1. A2 is A4's mother and A3 is A5's mother. The year of birth and thus the probable age of the two juveniles were estimated from their growth curve determined by means of a photogrammetric technique. These observations indicate that at Crozet Archipelago, juvenile killer whales first practiced intentional stranding on their own when they were 4-5 years old. Their first attempt to capture elephant seal pups by means of this technique was observed when they were 5-6 years old. However, 5- to 6-year-old juveniles still needed the assistance of an adult female to return to the water with their prey. This study indicates that learning hunting techniques needs a high degree of skill and requires high parental investment to reduce the associated risk. Furthermore, social transfer, through apprenticeship, is probably one of the mechanisms that enables the high degree of adaptability observed in killer whales.
Guinet, C., Y. Cherel, V. Ridoux and P. Jouventin (1996). Consumption of marine resources by seabirds and seals in Crozet and Kerguelen waters: changes in relation to consumer biomass 1962-85. Antarctic Science 8(1): 23-30.
The total annual food consumption of the seabird and seal community breeding at Iles Kerguelen was estimated to be 1.8x10 super(6) t in 1985. This biomass included c. 0.99x10 super(6) t (55%) of crustaceans, 0.46x10 super(6) t (26%) of myctophid fish, 0.07x10 super(6) t (4%) of other fish species, and 0.26x10 super(6) t (15%) of squid. During the same year, the mass of prey consumed in Crozet waters was previously estimated to be 3.1x10 super(6) t, the total food consumption in the Indian Ocean area including the two archipelagos thus totalling c. 5x10 super(6) in 1985. Four species of top predators, the king penguin, macaroni penguin, elephant seal, and fur seal, consumed 59% and 56% of the amount of prey eaten in 1985 by the whole community at Kerguelen and Crozet islands, respectively. Between 1962 and 1985, population changes of these four species induced 18 and 41% increases in their food consumption at Kerguelen and Crozet islands. Population changes included a moderate increase in the number of macaroni penguins and a marked rise of king penguin populations. Assuming that the diet of king penguin was similar in 1962 and 1985, its population increase will have required a concomitant increase of 0.6x10 super(6) t in the consumption of mycrophid fish in Crozet and Kerguelen waters.
Guinet, C., P. Jouventin and H. Weimerskirch (1999). Recent population change of the southern elephant seal at Iles Crozet and Iles Kerguelen: the end of the decrease ? Antarctic Science 11(2): 193-197.
The elephant seal populations breeding on the Iles Crozet and Kerguelen were regularly surveyed over the last three decades. At Iles Kerguelen the number of breeding females decreased at an annual rate of 3.6% between 1970 and 1987, then increased at an annual rate of 1.1% to 1997. At Iles Crozet, the population was reported to decrease at a rate of 5.35% between 1970 and 1990 but no change in numbers was found between 1990 and 1997. These results indicate that the rapid decline observed both at Iles Crozet and Iles Kerguelen has ended, and these populations are now either stable or slightly increasing. We suggest that broad scale change in environmental factors affecting the food availability for elephant seals may be responsible for the change in numbers of these marine predators. The higher rate of decrease, the longer period of decline, and the absence of any significant change between 1990 and 1997 observed on the Iles Crozet may be explained by additional factors such as killer whale predation.
Guinet, C., L. G. Barrett-Lennard and B. Loyer (2000). Co-ordinated attack behavior and prey sharing by killer whales at Crozet Archipelago: strategies for feeding on negatively-buoyant prey. Marine Mammal Science 16(4): 829-834.
Gulland, F. M. D., L. Werner, S. O'Neill, L. J. Lowenstine, J. Trupkiewitz, D. Smith, B. Royal and I. Strubel (1996). Baseline coagulation assay values for northern elephant seals (Mirounga angustirostris), and disseminated intravascular coagulation in this species. Journal of Wildlife Diseases 32(3): 536-540.
Coagulation assays, including platelet counts, antithrombin III, fibrinogen, fibrinogen degradation product levels, prothrombin (PT), activated partial thromboplastin (APTT) and activated clotting times (ACT), were performed on 20 healthy juvenile northern elephant seals (Mirounga angustirostris) stranded along the central California coastline from 15 March to 15 April 1994, to establish baseline parameters for this species. Elephant seals appear to have relatively short ACT, PT, and APTT times, while fibrinogen, platelet and antithrombin III levels are similar to domestic species. Based on these mean values in healthy animals, disseminated intravascular coagulation (DIC) was diagnosed in an elephant seal with low plasma fibrinogen and extended ACT, PT and APTT times; this animal had hemorrhages, mixed bacterial suppurative interstitial pneumonia with verminous arteritis, epicarditis, hepatitis and enterocolitis.
Gulland, F. M. D., K. Beckmen, K. Burek, L. Lowenstine, L. Werner, T. Spraker, M. Dailey and E. Harris (1997). Nematode (Otostrongylus circumlitus) infestation of northern elephant seals (Mirounga angustirostris) stranded along the central California coast. Marine Mammal Science 13(3): 446-459.
H
Hacker Sinclair, E. (1994). Prey of juvenile northern elephant seals (Mirounga angustirostris) in the Southern California Bight. Marine Mammal Science 10(2): 230-239.
Prey remains were identified from the stomach contents of 20 juvenile northern elephant seals (Mirounga angustirostris) that stranded in the Southern California Bight over a 14-yr period. The carcasses were in excellent condition, most having died just prior to necropsy.
Hakoyama, H., B. J. Le Boeuf, Y. Naito and W. Sakamoto (1994). Diving behavior in relation to ambient water temperature in northern elephant seals. Canadian Journal of Zoology 72( 4): 643- 651.
Our aim was to describe changes in ambient water temperature during the course of migration by northern elephant seals (Mirounga angustirostris) and to examine evidence for the seal using abrupt temperature gradients for locating prey. During migration in the post breeding season, the diving patterns of 10 adult females and 7 breeding-age males from Ano Nuevo, California, were recorded with time-depth recorders in 1989-1991. Recorded sea surface temperatures declined from 11-13 degree C to a low of 3-9 degree C as the seals moved north and increased as they returned. Depth of diving was not closely linked to sharp thermal gradients. A thermocline was evident only at the beginning and end of the migration in less than 100 m of water, where less than 2% of diving takes place. There were sex differences in the temperature range at the depths where 75% of diving and foraging occurred, owing in part to habitat separation. The temperatures were lower and the range narrower for females (4.2-5.2 degree C at 388-622 m) than for males (5.3-6.0 degree C at 179-439 m). We conclude that the northern elephant seal habitat does not provide abrupt changes in temperature that might serve as important cues for locating prey.
Haley, M. P. (1994). Resource-holding power asymmetries, the prior residence effect, and reproductive payoffs in male northern elephant seal fights. Behavioral Ecology and Sociobiology 34(6): 427-434.
The effect of resource-holding power (RHP) and prior residency asymmetries on fight outcome and subsequent seasonal copulatory success was analyzed for fights between marked male northern elephant seals (Mirounga angustirostris). RHP asymmetries were measured as differences in estimated mass and prior residency asymmetries were measured as differences in beach tenure prior to the fight. The principal results were: (a) Neither differences in mass nor differences in beach tenure had any effect on fight outcome as separate factors. (b) Mass and tenure differences had an interactive effect on fight outcome; fight winners were either heavier males present for shorter periods (intruders) or lighter males present for longer periods (prior residents). (c) Winners of fights copulated more often than losers after a fight throughout the breeding season; this difference was smallest for low-ranking males, larger for high-ranking males in short fights, and greatest for high-ranking males in long fights. (d) Prior resident males who won long fights obtained significantly more copulations after a fight than the males they defeated, but this was not true for intruder males who won long fights. These results suggest that male northern elephant seals will incur greater contest costs (i.e., fight for longer periods and/or against heavier males) for higher reproductive payoffs. They also imply that, at least for males in long fights, differences in prior residence represent payoff asymmetries, with higher reproductive payoffs for winning prior residents than for winning intruders.
Haley, M. P., C. J. Deutsch and B. J. Le Boeuf (1994). Size, dominance and copulatory success in male northern elephant seals, Mirounga angustirostris. Animal Behaviour 48(6): 1249-1260.
The relationship between size, dominance and copulatory success was investigated in male northern elephant seals to determine the importance of size in male intra-sexual competition for mates. The study was conducted over four breeding seasons at the Ano Nuevo rookery in central California. Mass was estimated using a photogrammetrical technique in three seasons and measured directly in one. Copulatory success was positively correlated with size (mass and length). This correlation was mediated through the positive effect of size on dominance rank; variation in arrival mass, for example, accounted for 29-44% of the variation in dominance. Copulatory success was positively correlated with dominance rank for mid- to high-ranking males, but not for low-ranking males, which obtained few copulations. Copulatory success was not significantly correlated with size when the effect of dominance was removed statistically. These results support the hypothesis that male reproductive success in this species is principally determined by dominance rank, which, in turn, is affected by male size. However, they also suggest that large size is just one of a number of important factors that affect the outcome of male intra-sexual competition and hence, reproductive success.
Hall, A. J., G. H. Engelhard, S. M. Brasseur, A. Vecchione, H. R. Burton and P. J. Reijnders (2003). The immunocompetence handicap hypothesis in two sexually dimorphic pinniped species--is there a sex difference in immunity during early development? Dev Comp Immunol 27(6-7): 629-37.
The 'immunocompetence handicap hypothesis' predicts that highly sexually dimorphic and polygynous species will exhibit sex differences in immunity. We tested this hypothesis in southern elephant and grey seals during their early development by measuring the following parameters: leucocyte counts, serum IgG levels, erythrocyte sedimentation rate and haematocrit. We failed to find any differences due to sex as assessed by the parameters investigated. Animals were sampled longitudinally during their development and there were significant age effects from birth to weaning in both species. Total and differential leucocyte counts and erythrocyte sedimentation rates increased just prior to weaning then decreased. Haematocrits declined whilst total circulating immunoglobulin G concentrations increased. Body temperatures remained constant throughout the postnatal period. Differences between the species were seen in total leucocyte counts and in polymorphonuclear cells and eosinophils. Southern elephant seals had higher concentrations than grey seals and total leucocyte counts in the former were among the highest reported for mammals.
Hamilton, J. E. (1940). On the history of the elephant seal, Mirounga leonina (Linn.). Proceedings of the Linnean Society of London 1939-40: 33-37.
Hamilton, J. E. (1949). Weight, etc., of elephant seal. Nature 163: 536.
Hanni, K. D. and P. Pyle (2000). Entanglement of pinnipeds in synthetic materials at south-east Farallon Island, California, 1976-1998. Marine Pollution Bulletin 40(12): 1076-1081.
Entanglement records of hauled out pinnipeds are useful for monitoring trends in impacts of synthetic materials, a principal contaminant, upon pinniped populations. This report documents entanglement of five species (California Sea Lions, Northern Elephant Seals, Steller Sea Lions, Pacific Harbor Seals, and Northern Fur Seals) at South-east Farallon Island (SEFI), an island in Northern California, 1976-1998, when a total of 914 pinnipeds were observed entangled in or with body constrictions from synthetic material. There was a significant decrease in entangled Northern Elephant Seals over the study period. Of the 27 Steller Sea Lions observed entangled, 37% were adult Steller Sea Lions entangled in salmon fishing gear. This report highlights an ongoing problem of entanglement of pinnipeds in synthetic materials in Northern California.
Harvey, J. T. and G. A. Antonelis (1994). Biases associated with non-lethal methods of determining the diet of northern elephant seals. Marine Mammal Science 10(2): 178-187.
The objectives of this study were to determine difference between quantity and size of prey fed to northern elephant seals (Mirounga angustirostris) and that estimated from stomach lavage and feces, and to determine potential biases associated with samples food habits of elephant seals using lavage.
Hatfield, B. B. and G. B. Rathbun (1999). Interactions between northern elephant seals and vehicles near Point Piedras Blancas, California. Marine Mammal Science 15(2): 598-600.
Northern elephant seals, Mirounga angustirostris, were nearly extirpated in the late 19th and early 20th centuries. However, they have recovered to the point where they are now locally abundant (Stewart et al. 1994). Stimulated by the report of human/northern elephant seal interactions in Baja California Sur (Webster and Baird 1998), we report here on an unusual terrestrial example of the increasing conflict between the growing populations of these two species in central California.
Heath, M. E. and R. J. Schusterman (1975). "Displacement" sand flipping in the Northern elephant seal (Mirounga angustirostris). Behavioral Biology 14: 379-385.
Hedrick, M. S., D. A. Duffield and L. H. Cornell (1986). Blood viscosity and optimal hematocrit in a deep-diving mammal, the northern elephant seal (Mirounga angustirostris ). Canadian Journal of Zoology J. Can. Zool. 64( 10): 2081- 2085.
Elephant seals (Mirounga angustirostris ) offer a unique opportunity to examine rheological characteristic of blood because of the normally high hematocrits in the species. A comparison of blood viscosity of the elephant seal with that of a terrestrial mammal (rabbit; reveals a threefold increase in viscosity of elephant seal blood over that of rabbit blood due to the high hematocrit). While the increased hematocrit of elephant seal blood reflects increased oxygen storage capacity, blood oxygen transport may actually be reduced by the effects of increased blood viscosity on blood flow. The results suggest that elephant seals have increased oxygen storage capacity at the expense of optimizing oxygen transport. The observed increase in hematocrit and viscosity may be of importance in considering the diving behavior and energetics of elephant seals.
Hedrick, P. W. (1995). Elephant seals and the estimation of a population bottleneck. Journal of Heredity 86(3): 232-235.
Heimark, R. J. and G. M. Heimark (1986). Southern elephant seal pupping at Palmer Station, Antarctica. Journal of Mammalogy 67(1): 189-190.
The occurrence of southern elephant seals at Palmer Station was first documented in 1955. Pupping and breeding were not observed and the population was thought to consist of only feeding and molting animals. This article reports the occurrence of elephant seal pupping at Palmer Station in Oct. and Nov. 1983. Observations of elephant seals taken in the immediate vicinity of Palmer Station were recorded daily from Dec. 7, 1982 until Dec. 6, 1983. Islands within a 4 km radius of the station were surveyed weekly for elephant seals from Dec. 1982 to Apr. 1983. On Oct. 11, four elephant seals were observed on a small group of islets in Arthur Harbor called Elephant Rocks. Two cows each bore a pup on Oct. 15. Also present on the islet were two breeding size bulls. Another pregnant cow arrived which gave birth between Oct. 17 and 19. A fourth cow and pup were discovered Nov. 9. The pupping was estimated to occur on Nov. 4 or 5, based on the condition of the umbilicus. The first two cows weaned their pups and departed the islet by Nov. 9. Their pups departed by Nov. 16. This suggests a weaning age of about 24 days. The third cow departed Nov. 20 and the fourth departed by Nov. 23.
Hindell, M. A. and H. R. Burton (1987). Past and present status of the southern elephant seal (Mirounga leonina) at Macquarie Island. Journal of Zoology London 213: 365-380.
The southern elephant seal population at Macquarie I. has undergone a serious decline since regular surveys were commenced in 1949. Approximately 2,900 cows and 250 bulls were counted in the isthmus study area during the 1985 breeding season. Comparisons with 20 other counts made in the same area between 1949 and 1984 showed that, although there was considerable fluctuation between the years, the number of seals ashore has dropped at an average rate of 2.1% per year, resulting in a net decrease of approximately 50% for both males and females. This is similar to the ratio of decline of elephant seal populations in the southern Indian Ocean. The census information from all major elephant seal populations was reviewed and it was concluded that there may be a common factor, or group of factors, acting to reduce the Macquarie I. and Indian Ocean populations, while the populations of the South Atlantic seem to be stable. Several potential explanations for these observations are advanced, but it is concluded that a greater knowledge of the ecology of the seals is needed if the declines are to be understood. (Auth.)
Hindell, H. A. and H. R. Burton (1988). Seasonal haul-out patterns of southern elephant seal (Mirounga leonina Linn.) at Macquarie Island. Journal of Mammalogy 69: 81-88.
Numbers of male, female, and juvenile southern elephant seals (Mirounga leonina) hauled out on the isthmus of Macquarie I. were monitored for 14 months. Most haul-out patterns could be described by a normal distribution function. The value of using these normal distribution equations as predictive models was assessed. Equations describing the number of breeding females and the number of pups produced were found to be the most precise. Haul-outs from other years at Macquarie I., and from other populations were compared by means of parameters calculated by the function. It was concluded that there has been little change in the order or duration of haul-outs at Macquarie I. since the 1950s, and that there is remarkable synchrony in the timing of the haul-out of breeding females in all major southern elephant seal populations. (Auth.)
Hindell, M. A. and H. R. Burton (1988). The history of the elephant seal industry at Macquarie Island and an estimate of the pre-sealing numbers. Proc. Roy. Soc. Tasmania 122(1): 159-176.
A comprehensive list is presented of all sealing ships that visited Macquarie I. between 1810 and 1919 with, where possible, their cargoes. Approximately 207 sealing visits were made to Macquarie I. in 109 years and an estimated 8380 tons of elephant seal oil removed. The major sealing effort seems to have been in the first 20 years, between 1810 and 1829, when almost half of the voyages occurred and over half of the oil was collected. For the present study, a mathematical model was devised to examine the responses of the population to the estimated annual harvest of seals from 1810-29. Given the often incomplete nature of the sealing records, accurate estimates of the pre-sealing elephant seal population were impossible to obtain, but the model suggests that it may have been in the region of 93,000 to 110,000 animals. The major impact of sealing activity was between 1820 and 1830, when the population was reduced by approximately 70%. Numbers are thought to have recovered to near pre-sealing levels by the 1900's, when the level of sealing was within the sustainable yield of the population.
Hindell, M. A. and H. R. Burton (1988). Seasonal haul-out patterns of the southern elephant seal (Mirounga leonina L.), at Macquarie Island.
Hindell, M. A. and G. J. Little (1988). Longevity, fertility and philopatry of two females Southern elephant seals (Mirounga leonina) at Macquarie Island. Marine Mammal Science 4(2): 168-171.
In 1950 the Australian Antarctic Division in conjunction with the Commonwealth Scientific and Industrial Research Organization (CSIRO) Division of Wildlife Research commenced a long-term branding study of the southern elephant seal at Macquarie Island (54 degree S, 159 degree E). Between 170 and 820 newly weaned pups were branded with hot irons each year from 1950 through 1965. The sample of known age animals has been the basis of much of the current knowledge of the ecology of this species. Although marking was discontinued after 1965, members of subsequent expeditions to the island continued to resight and record marked animals through the 1970s; afterwards resights became sporadic. Here the authors report observations of two branded cows in 1985.
Hindell, M. A. (1991). Some life history parameters of a declining population of southern elephant seals, Mirounga leonina. Journal of Animal Ecology 60: 119-134.
(1) Mark-resight data were analysed for thirteen cohorts from a declining population of southern elephant seals branded at Macquarie Island between 1951 and 1965. (2) First year survival was essentially stable during the 1950s at ahout 46% for females and 42% for males. There was a dramatic fall in first year survival during the 1960s, declining to less than 2% for both sexes in 1965. Post-year-l survival did not change between the 1950s and the 1960s. (3) Comparisons with a stable population of southern elephant seals at South Georgia indicated that both first year and adult survival were lower in the Macquarie Island population. There were no changes in the age at first breeding of the Macquarie Island seals during the study, but this was on average 1 year later than at South Cieorgia. (4) It is hypothesized that the current decline in elephant seal numbers at several of their major breeding islands is due to the populations returning to pre-sealing levels after they had risen to abnormally high levels with the end of commercial exploitation early this century. (5) Possible tests of the hypothesis include studying the diet and foraging behaviour of southern elephant seals to gain an understanding of the predator-prey relationships, continuing to census the Macquarie Island population to determine if the population levels out at around the estimated pre-sealing levels, and monitoring northern elephant seal populations which were also severely exploited but are currently increasing rapidly.
Hindell, M. A., D. J. Slip and H. R. Burton (1991). The diving behaviour of adult male and female southern elephant seals, Mirounga leonina (Pinnipedia: Phocidae). Australian Journal of Zoology 39(5): 593-619.
Over 50,000 individual dive records collected by time-depth recorders were analysed with respect to sex of the seal, time of year and the approximate geographic location of the dive. Sex distinct dive types were described on the basis of parameters such as the amount of time spent at the maximum depth of the dive, the rate of ascent and descent, and the general form of the dive profile. These dive types were "rest" dives, "travel" dives, "surface" dives, "general non-foraging" dives, "pelagic foraging" dives and "benthic foraging" dives. The seals spent 90% of their time at sea submerged. Less than 2% of the time was spent on the surface in intervals of more than 10 min. A further 20-30% of the time was spent on the various non-foraging types of dives.
Abstract modificato CRB
In this study on elephant seals, over 50,000 individual dive records collected by time-depth recorders were analyzed with respect to sex of the seal, time of year and the approximate geographic location of the dive. Six distinct dive types were described on the basis of parameters such as the amount of time spent at the maximum depth of the dive, the rate of ascent and descent, and the general form of the dive profile. These dive types were 'rest' dives, 'travel' dives, 'surface' dives, 'general non-foraging' dives, 'pelagic foraging' dives and 'benthic foraging' dives. The seals spent 90% of their time at sea submerged. Less than 2% of the time was spent on the surface in intervals of more than 10 min. A further 20-30% of the time was spent on the various non-foraging types of dives. Most females performed only 'pelagic foraging' dives, while males performed both 'pelagic' and 'benthic foraging' dives. All the 'benthic foraging' dives occurred in Area 3 (defined by water-temperature data as lying over the Antarctic Continental Shelf) and were 400-500 m deep. 'Pelagic foraging' dives occurred in all three foraging areas and ranged in depth from 200 to 1100 m. These types of dives also exhibited marked diurnal variations in depth, unlike 'benthic foraging' dives. The seals spent 10-20 min at the bottom of each 'foraging' dive, where they generally displayed a series of small changes in depth ('wiggles').
Hindell, M. A., D. J. Slip, H. R. Burton and M. M. Bryden (1992). Physiological implications of continuous, prolonged, and deep dives of the southern elephant seal (Mirounga leonina ). Canadian Journal of Zoology J. Can. Zool. 70( 2): 370- 379.
The diving behaviour of 14 adult southern elephant seals was investigated using time depth recorders. Each of the seals performed some dives that were longer than its theoretical aerobic dive limit. Forty-four percent of all dives made by postmoult females exceeded the calculated limit compared with 7% of those made by postbreeding females and less than 1% of those made by adult males. The extended dives displayed characteristics that suggested that they were predominantly foraging dives, although some were apparently rest dives. Dives longer than the calculated aerobic limits often occurred in bouts; the longest consisted of 63 consecutive dives and lasted 2 days. Postmoult females performed longer bouts of extended dives than postbreeding females. Extended surface periods (longer than 30 min) were not related to the occurrence of extended dives or bouts of extended dives. The possible physiological mechanisms that permit such prolonged continuous dives are discussed. Southern elephant seals may increase the aerobic capacity of dives by lowering their metabolism to approximately 40% of the resting metabolic rate on long dives. There is substantial interseal variability in the methods used to cope with long dives.
Hindell, M. A., M. M. Bryden and H. R. Burton (1994). Early growth and milk composition in southern elephant seals (Mirounga leonina). Australian Journal of Zoology 42(6): 723-732.
Growth rates and changes in body composition of pups were monitored during the 3-week lactation period of southern elephant seals (Mirounga leonina) at Macquarie Island. Despite a slight decrease in weight in the first days post-partum, pups attained a mass of 114 plus or minus 16.6 kg (mean plus or minus s.d.) at weaning, representing an average growth rate of 3.53 plus or minus 0 80 kg/day over the entire lactation period. The proportion of body mass represented by fat was less than 3% at birth, increasing to 40.8 plus or minus 12.7% at weaning. Lean tissue mass altered little for most of the lactation period, but did show an increase in the last four days. The fat content of the milk reflected these changes, starting at 16.1 plus or minus 6.98% on Day 1 of lactation and increasing to 39.5 plus or minus 15.2% about the time of weaning. Fat content of the milk was, however, highly variable and at weaning ranged from 7% to 55%. Although the growth rate of the pup was correlated with mass lost by its mother during lactation, there was no relationship between maternal mass and weaning weight of pups. It is suggested that growth rates may be related to maternal condition and not simply mass, and, further, that differences in growth rates between populations of southern elephant seals are related to maternal energy reserves.
Hindell, M. A., D. J. Slip and H. R. Burton (1994). Possible causes of the decline of southern elephant seal populations in the southern Pacific and southern Indian ocean. Elephant seals. Population ecology, behavior and physiology. B. J. L. B. R. M. Laws. Berkeley (CA), Un. California Press: 66-84.
Several characteristics of declining southern elephant seal populations provide a basis for the formulation and testing of hypotheses designed to explain the decline. Some populations seem to be declining independently of other major southern ocean vertebrate consumers, but only two of the three distinct stocks have exhibited a decline. Studies conducted in the 1950s and 1960s indicate that elephant seals from Macquarie I. had lower survivorship and slower growth rates and reached sexual maturity later than those from South Georgia. Survival of first-year seals decreased dramatically during the 1960s and led to the near total failure of the 1965 cohort; the fate of later cohorts has not been determined. Two main hypotheses are advanced, one involving equilibration processes after intense sealing pressure and the other concerned with fluctuations in the ocean environment. However, while there may be a single driving factor influencing the populations of southern elephant seals in the Indian and Pacific Ocean sectors, there may be additional local factors that also regulate the populations. (Auth. mod.)
Hindell, M. A., D. J. Slip and H. R. Burton (1994). Body mass loss of moulting female southern elephant seals, Mirounga leonina, at Macquarie Island. Polar Biology 14(4): 275-278.
Thirteen female southern elephant seals moulting at Macquarie I. lost an average of 4.46 kg/day (10.01 g/kg/day). There was no significant difference between this rate of body mass loss and that reported for moulting female southern elephant seals from South Georgia. Moulting female southern elephant seals however exhibited larger specific mass loss than either female northern elephant seals or male southern elephant seals, indicating a higher metabolic cost of moult in these animals.
Hindell, M. A. and D. J. Slip (1997). The importance of being fat: maternal expenditure in the southern elephant seal Mirounga leonina. Marine mammal research in the Southern Hemisphere. Volume 1. M. Hindell: 72-77.
Hindell, M. A. and M.-A. Lea (1998). Heart rate, swimming speed, and extimated oxygen consumption of a free-ranging southern elephant seal. Physiological Zoology 71(1): 74-84.
Heart rate, swimming speed, and diving behaviour were recorded simultaneously for an adult female southern elephant seal during her postbreeding period at sea with a Wildlife Computers heart-rate time depth recorder and a velocity time depth recorder. The errors associated with data storage versus real-time data collection of these data were analysed and indicated that for events of short duration (i.e., less than 10 min or 20 sampling intervals) serious biases occur. A simple model for estimating oxygen consumption based on the estimated oxygen stores of the seal and the assumption that most, if not all, dives were aerobic produced a mean diving metabolic rate of 3.64 mL O2 kg-1, which is only 47% of the field metabolic rate estimated from allometric models. Mechanisms for reducing oxygen consumption while diving include cardiac adjustments, indicated by reductions in heart rate on all dives, and the maintenance of swimming speed at near the minimum cost of transport for most of the submerged time. Heart rate during diving was below the resting heart rate while ashore in all dives, and there was a negative relationship between the duration of a dive and the mean heart rate during that dive for dives longer than 13 min. Mean heart rates declined from 40 beats min-1 for dives of 13 min to 14 beats min-1 for dives of 37 min. Mean swimming speed per dive was 2.1 m s-1, but this also varied with dive duration. There were slight but significant increases in mean swimming speeds with increasing dive depth and duration. Both ascent and descent speeds were also higher on longer dives.
Hindell, M. A., B. J. Mcconnell, D. J. Slip, M. A. Fedak, H. R. Burton and P. J. H. Reijnders (1998). Diving behaviour in newly-weaned southern elephant seals during their first trip to sea. World Marine Mammal Science Conference Monaco, Lawrence, KS, Society for Marine Mammalogy.
Hindell, M. A., B. J. McConnell, M. A. Fedak, D. J. Slip, H. R. Burton, P. J. H. Reijnders and C. R. McMahon (1999). Environmental and physiological determinants of successful foraging by naive southern elephant seal pups during their first trip to sea. Canadian Journal of Zoology 77(11): 1807-1821.
The ability to forage successfully during their first trip to sea is fundamental to the ultimate survival of newly weaned southern elephant seals (Mirounga leonina). However, there is considerable variation in the body mass and fat content of seal pups at weaning, which results in some individuals having larger energy and oxygen stores than others, which may confer advantages on them. The diving behaviour of 21 newly weaned seals was studied using satellite relayed data loggers. Seals were captured at Macquarie Island in December 1995 and 1996, approximately 4 weeks after weaning. Two groups of seals were specifically targeted: a heavy group from the top quartile of weaning masses (n = 6) and a light group from the lower quartile (n = 15). Most of the seals made dives in excess of 100 m depth and 5 min before final departure from the island. However, for the first 60-80 d, all of the seals exhibited behaviour quite distinct from the patterns reported for older conspecifics, and made relatively shallow (100 ± 39 m; mean ± SD) and short (5.7 ± 1.23 min) dives. During this time the seals spent 74.3 ± 12.6% of each day diving, and the depth of the dives did not follow any diurnal pattern. The diving behaviour of all seals changed abruptly when they started on their return to land. During this time their behaviour was more like that of adults: they made deeper (159 ± 9 m) and longer dives (9.01 ± 1.69 min) than previously, and the dives showed a strong diurnal pattern in depth. There is no obvious explanation for this change in behaviour, although its abrupt nature suggests that it is unlikely to have been due to physiological changes in the seals. The size of the seals at weaning was an important influence on diving behaviour. Heavy weaners made significantly deeper (130 ± 40 m) and longer dives (7.36 ± 0.55 min) than light weaners (88 ± 32 m and 5.04 ± 0.64 min, respectively). This indicates that smaller seals are constrained to some extent by their physiological capabilities, which perhaps requires some individuals to adopt different foraging strategies.
Hindell, M. A., M.-A. Lea, M. G. Morrice and C. R. MacMahon (2000). Metabolic limits on dive duration and swimming speed in the southern elephant seal Mirounga leonina. Physiological and Biochemical Zoology 73(6): 790-798.
The ability of air-breathing marine predators to forage successfully depends on their ability to remain submerged. This is in turn related to their total O(2) stores and the rate at which these stores are used up while submerged. Body size was positively related to dive duration in a sample of 34 adult female southern elephant seals from Macquarie Island. However, there was no relationship between body size and dive depth. This indicates that smaller seals, with smaller total O(2) stores, make shorter dives than larger individuals but operate at similar depths, resulting in less time being spent at depth. Nine adult female elephant seals were also equipped with velocity time depth recorders. In eight of these seals, a plot of swimming speed against dive duration revealed a cloud of points with a clear upper boundary. This boundary could be described using regression analysis and gave a significant negative relationship in most cases. These results indicate that metabolic rate varies with activity levels, as indicated by swimming speed, and that there are quantifiable limits to the distance that a seal can travel on a dive of a given swimming speed. However, the seals rarely dive to these physiological limits, and the majority of their dives are well within their aerobic capacity. Elephant seals therefore appear to dive in a way that ensures that they have a reserve of O(2) available.
Hindell, M. A. and C. R. McMahon (2000). Long distance movement of a southern elephant seal (Mirounga leonina) from Macquarie Island to Peter 1 Oy. Marine Mammal Science 16(2): 504-507.
On 26 February 1999 a branded juvenile southern elephant seal, Mirounga leonina, was observed on Peter 1 Oey (Peter the First Island, 68 degree 51'S, 90 degree 35'W) during a visit by the icebreaker Kapitan Khlebnikov. The female seal was aged 16 mo, and was branded as a newly weaned pup at Macquarie Island (54 degree 30'S, 158 degree 50'E), in November 1997. The condition of its coat indicated that the seal was ashore for its annual molt, and the brand (M670) was in good condition and clearly readable. Peter 1 Oey is approximately 5,200 km east of Macquarie Island and has rarely been visited; ours was the only the tenth recorded landing. 95% of the island's 157 km super(2) is permanently glaciated, with some small narrow beaches on the western side where small numbers of elephant seals haul out. This is the longest recorded movement for a southern elephant seal. This seal was seen back at Macquarie Is. 88 d later, on 21 May 1999. The seal must have used a minimum rate of travel of 59 km/d to return in that time.
Hindell, M. A., C. J. A. Bradshaw, M. D. Sumner, K. J. Michael and H. R. Burton (2003). Dispersal of female southern elephant seals and their prey consumption during the austral summer: relevance to management and oceanographic zones.
1. Numerical models that predict trophic structure require both accurate information on prey consumption rates and estimates of spatial and temporal variation. In the Southern Ocean little information exists on the spatial and temporal patterns of resource use by predators, so we attempted to examine these patterns for an important Antarctic predator, the southern elephant seal. We (i) defined the area of the ocean used by the adult female component of the elephant seal population at Macquarie Island; (ii) quantified the time these seals spent in the different regions of the Southern Ocean; and (iii) estimated the biomass of fish and squid prey consumed per fortnight and per region. 2. We used data from 42 post-breeding females collected from 1992 to 2001. The data consisted of locations determined by geo-location (based on light intensity) recorded using dataloggers. A randomized, incremental analysis of at-sea locations indicated that a sample of 25 individuals was required to provide 95% coverage of the total area of ocean used. 3. The greatest amount of time (44 times 6%) was spent in the region between the Antarctic Polar Front (APF) and the Subantarctic Front (SAF). Up to 20% of time was spent south of the Antarctic Circle or within Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) Statistical Subareas, indicating that seals from Macquarie Island are also important summer-time predators in high Antarctic waters. 4. The adult female population was estimated to consume 122 times 73-125 times 81 x 10 super(6) MJ for the post-lactation foraging trip (31 142-31 925 tonnes of prey). Of this, 47 times 2-53 times 4% was consumed within the CCAMLR Statistical Subareas and the Australian and New Zealand exclusive economic zones (EEZ). 5. Synthesis and applications. Our study emphasizes that (i) a large sample of individual seals (25) can estimate spatial trends in prey consumption; (ii) much of the estimated prey consumption occurs within fishery-managed zones, therefore elephant seals should be included in models predicting trophic structure in the Southern Ocean; and (iii) recent commercial fishery catch within these zones is minimal relative to the prey consumed by elephant seals, but increases in fishing activity in these zones may result in competition for marine resources.
Hochachka, P. W. (1992). Metabolic biochemistry and the making of a mesopelagic mammal. Experientia. 48( 6): 570- 575.
Large seals such as northern and southern elephant seals and Weddell seals are able to dive for startling duration and enormous depth. The current dive duration record is 120 minutes (recorded for the southern elephant seal); the current depth record is 1.5 km (recorded for the northern elephant seal). Equally striking is the widespread observation that these seals when at sea spend close to 90% of the time submerged and often at great depth. For practical purposes, these species can be viewed as true mesopelagic animals when they are at sea. A review of current knowledge indicates that low power output but high efficiency metabolic functions of skeletal muscles coupled with inherently low (and potentially further suppressible) metabolic rates constitute strategic biochemical components in the "making" of a mesopelagic mammal.
Hochachka, P. W. and R. A. Foreman, III (1993). Phocid and cetacean blueprints of muscle metabolism. Canadian Journal of Zoology 71( 10): 2089-2098.
Large seals, such as northern and southern elephant seals and Weddell seals, are able to dive for unexpected lengths of time and to enormous depth. The current dive-duration record is 120 min (recorded for the southern elephant seal); the current depth record is 1.5 km (recorded for the northern elephant seal). Equally striking is the widespread observation that these seals, when at sea, spend close to 90% of the time submerged and often at great depth. For practical purposes, these species can be viewed as true mesopelagic animals when they are at sea. Analysis of current knowledge indicates that enzyme adaptations in chronic hypobaric hypoxia are directed mainly towards up-regulation of metabolic efficiencies. Evidence that similar metabolic adjustments are utilized by seals was obtained by profiling the maximum enzyme activities of four phocid species (harbor seal, Weddell seal, crabeater seal, leopard seal) and one cetacean (fin whale). In the seals, the patterns obtained were strikingly similar to those of hypobaric hypoxia adaptations. The extensive enzyme data obtained on seals, however, showed notably different patterns from those found in whale muscles. The data from the large seals were consistent with the concept that low power output but high-efficiency metabolic functions of skeletal muscles coupled with inherently low (and potentially further suppressible) metabolic rates constitute strategic biochemical components in the design of a mesopelagic mammal.
Hodder, J., R. F. Brown and C. Cziesla (1998). The northern elephant seal in Oregon: a pupping range extension and onshore occurrence. Marine Mammal Science 14(4): 873-881.
The northern elephant seal, Mirounga angustirostris, has undergone a phenomenal population growth in the past 100 yr, recovering from a population that numbered tens or perhaps low hundreds at the turn of the century to an estimated 127,000 individuals in 1991 (Stewart et al. 1994). Northern elephant seals have now reoccupied many of their former breeding sites (Radford et al. 1965, Odell 1971, Stewart and Yochem 1986) and are continuing to expand their breeding range (Stewart et al. 1994). In 1981 elephant seals established a breeding colony on the Point Reyes mainland, a site at which there is no historical evidence for breeding (Allen et al. 1989). In this paper we discuss a further expansion of the pupping range of the northern elephant seal to Shell Island, Cape Arago, Oregon (43 degree 18 theta 45 double prime N, 124 degree 24 theta 5 double prime W). When not on land for breeding or molting, elephant seals range widely in the northern Pacific ocean and are present offshore of Oregon during a large portion of the year (Stewart and De Long 1995). We examine the recent history and pattern of onshore occurrences by northern elephant seals in Oregon.
Hoelzel, A. R. (1991). Killer whale predation on marine mammals at Punta Norte, Argentina; Food sharing, provisioning and foraging strategy. Behavioral Ecology and Sociobiology 29( 3): 197- 204.
The social dynamics of killer whales (Orcinus orca ) that hunt marine mammals are apparently highly flexible, though strong individual associations do exist. The killer whales at Punta Norte offer an unusually detailed view of association patterns and foraging behaviour, and suggest a pattern of behaviour that optimizes hunting efficiency with exception only to strong associations between some individuals and the provisioning and training of offspring. The main points from this paper are as follows: First, hunting effort was concentrated where the capture rate was greatest. All pods selectively attacked the prey type for which they had the highest capture rate. The amount of southern sea lion prey captured was approximately equal to the estimated minimum energetic requirement for killer whales based on weight. Secondly, one whale in each pod did the majority of the hunting, and then provisioned the others in the pod. It was clear on numerous occasions the food was shared.
Hoelzel, A. R., J. Halley, S. J. O'Brien, C. Campagna, T. R. Arnbom, B. J. Le Boeuf, K. Ralls and G. A. Dover (1993). Elephant seal genetic variation and the use of simulation models to investigate historical population bottlenecks. J. Heredity 84: 443-449.
Because the northern elephant seal (Mirounga angustirostrus) was heavily exploited during the 19th century, it experienced an extreme population bottleneck. Since then, under legislative protection in the United States and Mexico, northern elephant seals have recovered dramatically in number, although their genomic diversity was greatly reduced, apparently as a consequence of the bottleneck. In this study we investigated DNA sequence diversity in two mtDNA regions (the control region and 16S RNA) and found low genetic variation in the northern elephant seal: there were only two control region haplotypes (sequence difference = 1%), which was consistent with an extreme founder event in the recent history of the northern species. We also reaffirmed the lack of allozyme diversity in this species. In contrast, the southern elephant seal (M. leonina), which though similarly exploited never fell below 1,000 animals, had 23 control region mtDNA haplotypes (average sequence difference = 2.3%). To investigate the extent of the founder event in the northern elephant seal we devised a simulation model based on extensive demographic data. This allowed a statistical analysis of the likely outcome of bottlenecks of different size and duration. Given these historical data, our results indicate (within 95% confidence) a bottleneck of less than 30 seals and 20-year duration, or, if hunting was the primary pressure on the population, a single-year bottleneck of less than 20 seals.
Hoelzel, A. R. (1999). Impact of population bottlenecks on genetic variation and the importance of life-history; a case study of the northern elephant seal. Biological Journal of the Linnean Society 68(1/2): 23-39.
This paper reviews some of the important factors related to the impact of population bottlenecks, using the northern elephant seal (Mirounga angustirostrus) as a case study for illustration. The northern elephant seal was hunted extensively in the 19th century and forced through a bottleneck of approximately 10-20 seals. All measures of molecular genetic variation show current levels for the northern elephant seal to be low. Levels of genetic variation were compared with expectations based on a simulation model that recapitulates demographic growth, based on age-specific data on reproduction and mortality. Predictions from the simulation model are then presented to illustrate the importance of differences in life-history strategy and skewed reproductive success. Either high reproductive skew (e.g. polygyny) or a low growth rate in a population can increase the impact of a bottleneck on molecular variation. Severe population bottlenecks can also disrupt aspects of developmental stability and thereby increase the fluctuating asymmetry and variability of quantitative traits. A comparison of skulls collected before and after the bottleneck showed this to have occurred for some elephant seal quantitative characters.
Hoelzel, A. R., B. J. Le Boeuf, J. Reiter and C. Campagna (1999). Alpha-male paternity in elephant seals. Behavioral Ecology and Sociobiology 46(5): 298-306.
The aim of this study was to assess paternity of males that dominated mating in harems at northern (Mirounga angustirostris) and southern (M. leonina) elephant seal rookeries using DNA fingerprinting and microsatellite DNA analysis. Southern alpha males had greater reproductive success than most northern alphas at similar-sized harems. Comparison of the relatedness between pups within harems also suggested that fewer males achieved matings in the southern elephant seal population. This was consistent with behavioral observations that suggest greater competition for mates in northern elephant seal harems. Reproductive success was consistent with estimates of mating success in some cases, but lower than expected for some northern elephant seal alpha males. A lower reproductive success than predicted from mating behavior may arise from a variety of factors including sperm competition, male sperm depletion from frequent mating, or reduced fertility. The alternatives are discussed in the context of environmental and historical factors.
Key words Mating system , Paternity testing , Elephant seals , Molecular ecology
Hoelzel, A. R., C. Campagna and T. Arnbom (2001). Genetic and morphometric differentiation between island and mainland southern elephant seal populations. Proceedings Royal Society of London Series B Biological Sciences 268(1464): 1-8.
We compare genetic (both nuclear and mitochondrial) and morphometric measures between two putative populations of southern elephant seal (Mirounga leonina), and interpret the results in the context of data from mark-recapture and satellite-telemetric studies. One population is on the Argentine mainland, while the other is 2400 km away on South Georgia island. We found pronounced di¡erentiation at the mitochondrial DNA (mtDNA) control region that was distinct from the pattern of variation seen among island rookeries. Some morphometric characters and seven out of ten nuclear-DNA markers also showed di¡erentiation between the island and mainland sites. Diversity at nuclear markers was high in both populations but mtDNA diversity was low in the mainland population, suggesting a founder event and little subsequent immigration of females. Morphological differences may suggest di¡erent selective environments at the two sites.
Keywords: population genetics; morphometrics; dispersal; demography; marine mammals
Honigman, L. (1988). Mating strategies in southern elephant seals, Mirounga leonina. Santa Cruz (California), University of California Santa Cruz.
Houser, D. S. and D. P. Costa (2001). Protein catabolism in suckling and fasting northern elephant seal pups (Mirounga anglstirostris). J Comp Physiol [B] 171(8): 635-42.
Nursing elephant seal pups are hypothesized to be preadapted to the postweaning fast, yet no comparison of lipid or protein use for meeting metabolic costs has been made between these contrasting nutritional periods. To address this, protein catabolism was estimated in five elephant seal pups from measurements of urea turnover made twice during nursing and twice during the postweaning fast. Changes in body composition were measured in ten separate weaned pups via tritiated water dilution and matched to fasting urea turnover measurements in order to assess errors in protein catabolism derived from urea turnover rates. Estimates of lean mass loss based upon urea turnover and tritiated water dilution were in general agreement, supporting estimates of protein catabolism derived from urea turnover measurements. Protein catabolism was estimated to contribute less than 4% to the average metabolic rate of suckling and fasting pups implying strict protein conservation during both periods and supporting the shypothesis that suckling pups are pre-adapted to fasting. It is proposed that strict protein conservation across suckling and fasting compensates for relative reductions in maternal investment associated with the abbreviated lactation period of the elephant seal.
Houser, D. S., D. E. Crocker, P. M. Webb and D. P. Costa (2001). Renal function in suckling and fasting pups of the northern elephant seal. Comparative Biochemistry and Physiology Part A Molecular & Integrative Physiology 129A(2-3): 405-415.
Elephant seals fast for prolonged periods without access to water. This is made possible, in part, by reductions in urine production. However, the mechanisms involved in reducing urine production are not understood. In this study, glomerular filtration rate (GFR) was measured in five northern elephant seal pups (Mirounga angustirostris) via the inulin clearance technique. Measurements were made during day 9 and day 18-22 of nursing and the second and eighth week of the postweaning fast. Plasma aldosterone and cortisol concentrations, quantified by radioimmunoassay, were measured in eight other weanlings during the second and eighth week of the fast. Mean GFR was 79.3[plus/minus]29.3 ml/min during the early suckling period and 78.2[plus/minus]17.1, 89.8[plus/minus]52.7, and 80.4[plus/minus]12.2 ml/min during the late suckling, early fasting and late fasting periods, respectively. Differences between nursing and fasting were insignificant, possibly because reduced protein oxidation during suckling and rapid recruitment of protein for tissue synthesis obviated the need for postprandial hyperfiltration. Alternatively, maintenance of GFR during fasting may facilitate urea concentration by compensating for reductions in the fractional excretion of urea. It is further hypothesized that aldosterone is primarily responsible for mediating renal water reabsorption in this system.
Hoyles, L., G. Foster, E. Falsen, L. F. Thomson and M. D. Collins (2001). Facklamia miroungae sp. nov., from a juvenile southern elephant seal (Mirounga leonina). International Journal of Systematic and Evolutionary Microbiology 51(4): 1401-1403.
An unusual Gram-positive, catalase-negative, facultatively anaerobic, coccus-shaped organism that originated from a juvenile elephant seal was characterized by phenotypic and molecular taxonomic methods. Comparative 16S rRNA gene sequencing showed that the unknown coccus represents a new subline within the genus Facklamia. The unknown strain was readily distinguishable from all currently recognized species of the genus Facklamia (Facklamia hominis, Facklamia languida, Facklamia ignava, Facklamia sourekii and Facklamia tabacinasalis) by biochemical tests and electrophoretic analysis of whole-cell proteins. Based on phylogenetic and phenotypic evidence, it is proposed that the unknown bacterium be classified as Facklamia miroungae sp. nov. The type strain of F. miroungae is CCUG 42728T (=CIP 106764T). F. miroungae is the first member of the genus Facklamia to be isolated from an animal other than man.
Huber, H. R. (1987). Natality and weaning success in relation to age at first reproduction in northern elephant seals. Canadian Journal of Zoology 65: 1311-1316.
Huber, H. R., A. C. Rovetta, L. A. Fry and S. Johnston (1991). Age-specific natality of northern elephant seals at the South Farallon Islands, California. Journal of Mammalogy 72(3): 525-534.
We monitored 233 tagged, known-age female northern elephant seals (Mirounga angustirostris ), age 3-16 years, that gave birth on the South Farallon Islands, 1975-1986. Age-specific natality was significantly lower for 3- and 4-year olds (0.13 and 0.75, respectively), then stabilized at about 0.80 for females age 5-10 years. Natality was significantly lower in 1984 and 1985 than in other years. For the 1971-1980 cohorts, mean age at first reproduction ranged from 3.9 to 4.6 years. During this study, the age structure of females giving birth on the South Farallon Islands changed; mean age rose from 4 years in 1975 to 7 years in 1986. At least 20% of Farallon-born females survived to reproduce, greater than or equal to 17% returned to the South Farallon Islands, and greater than or equal to 3% emigrated to other rookeries. Females born at Ano Nuevo, San Miguel, and San Nicolas islands immigrated to the South Farallon islands to give birth (Ž3, Ž 2, and Ž1% respectively). Mature, nonpregnant females were seen during the breeding season (6%), during the autumn haul out (15%), and during spring molt or a later breeding season (79%).
Hughes, R. (1983). Elephant seal harvesting.
Hunt, J. F. (1973). Observations on the seals of Elephant Island, South Shetland Islands, 1970-71. BAS Bulletin 36: 99-104.
Several thousand elephant seals haul out at Elephant I. in the summer and breeding was confirmed by the presence of pups of the current season. Seven elephant seals tagged at South Georgia and one from the South Orkney Is. were seen. Evidence of fur seal breeding was obtained and at least 19 pups were born in the group this season at two locations. Over 300 fur seals, mainly adult bulls, were seen during the summer, the majority in four large concentrations. Other species are uncommon but observations were made on leopard seal hunting behavior.
Huntley, A. C. (1984). Relationships between metabolism, respiration, heart rate, and arousal states in the northern elephant seal. Department of Biology. Santa Cruz, California, University of California.
The northern elephant seal is the only animal known to cease ventilation during most or all of its sleep period. This sleep apnea closely mimics the physiological responses seen during diving in marine mammals. In addition to a decrease in heart rate, overall metabolism is reduced. This study investigates this finding and its adaptive significance to elephant seals constrained to fast on land during the reproductive season. Eight weaned elephant seal pups (30-35 days post weaning) taken from the beach at Ano Nuevo State Reserve were maintained in a fenced enclosure at the Long Marine Laboratory. Electroencephalograms, electromyograms, and electrocardiograms were recorded from stainless steel needle electrodes. A single eight hour continuous recording of all parameters was obtained from each animal. During these recordings, animals were restrained on a board with their heads in a metabolic hood. Oxygen consumption and respiration were continuously monitored. The elephant seal pups exhibited both slow wave and rapid eye movement sleep. They slept a mean of 27.1% of the time; 74.2% of this sleep showed no respiration. Sleep apneas ended with marked hyperventilation and tachycardia. The mean apnea was 3.9 minutes in length, the maximum duration was 7.75 minutes. A net energy savings accrued as a result of reduced metabolism during apnea was estimated by comparing the basal metabolic rate to the average metabolic rate. Sleep apnea resulted in a net savings of 23.2% of the basal metabolic rate.
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Ingham, S. E. (1967). Branding elephant seals for life-history studies. Polar Record 13(85): 447-449.
Iniguez, M. A. (2001). Seasonal distribution of killer whales (Orcinus orca) in Northern Patagonia, Argentina. Aquatic Mammals 27(2): 154-161.
Killer whales, Orcinus orca, have been studied since 1975 in Northern Patagonia, Argentina. In the present study from 1985 to 1997, individual animals were identified using photo-identification techniques. Boat and shore observations were conducted during both the austral summer-autumn season 1985-1997 and the austral winter season 1992-1993. Thirty killer whales have been identified in the study area since 1975 and some individuals use a 1000-km stretch of the Northern Patagonian coastline. A core group of 17 return to the area each year and were assigned to three groups based on association with other individuals. Prey has included South American sea lions (Otaria flavescens) and southern elephant seal (Mirounga leonina). The seasonal distribution of killer whales is correlated to the distribution of the South American sea lions and southern elephant seal in Northern Patagonia. Most encounters with the whales occurred in December and March-May (64.2% in 1995 and 69% in 1996) at Punta Norte, during the sea lions breeding cycle. Whales depart the area in May when pinnipeds migrate to winter rookeries. One pod, Patagonia Norte B (PNB) was photographed in Golfo San Jose on 9 January 1986 and in Punta Norte 1 day later, some 60 km apart. Larger pods (>three whales/pod) spent no more than five days in the same area, and smaller pods ([ltoreq]two whales/pods) stayed longer in the same area. Seasonal distribution of Patagonia Norte A and PNB pods was largely associated with the movement of South American sea lions, while Patagonia Norte C pod was more associated closer with the southern elephant seal movements.
Insley, S. J. (1992). Mother-offspring separation and acoustic stereotypy: A comparison of call morphology in two species of pinnipeds. Behaviour 120(1-2): 103-122.
I compared structural variation of the primary vocalizations used between mother-offspring pairs in two species of pinnipeds that differ fundamentally in their breeding behaviour: northern elephant seal (Mirounga angustirostris ) mothers and offspring normally are together throughout the nursing period; northern fur seal (Callorhinus ursinus ) females regularly separate from their offspring while nursing. Two predictions were tested: these vocalizations should be individually-distinct (stereotyped) in females and pups of both species if they serve to function for recognition, and because individuality should be more pronounced in a species where separations and reunions are common, the vocalizations used between northern fur seal mother-offspring pairs should be more individually-stereotyped than those of the northern elephant seal. The results indicate that selective pressure to develop vocal recognition exists in both species but is greater in the northern fur seal.
Irvine, L. G., M. A. Hindell, J. van den Hoff and H. R. Burton (2000). The influence of body size on dive duration of underyearling southern elephant seals (Mirounga leonina). Journal of Zoology 251(4): 463-471.
The dive duration of 16 underyearling (6-12 months old) southern elephant seals Mirounga leonina during their second trip to sea was investigated using geolocating time-depth recorders. Underyearling seals had a lesser diving ability, with respect to duration and depth, than adult southern elephant seals. Individual underyearlings dived for average durations of up to 20.3 min and depths up to 416 m compared to durations and depths of 36.9 min and 589 m, respectively for adults. Dive duration was positively related to their body mass at departure, indicating that smaller seals were limited to shorter dive durations, perhaps as a result of their lesser aerobic capacity. All seals often exceeded their theoretical aerobic dive limit (average of 22.1 plus or minus 18.1%). The number of dives exceeding the theoretical aerobic dive limit was not related to mass, suggesting that factors other than mass, such as foraging location or prey availability, may have been responsible for differences in diving effort. Foraging ability, indicated by the ability of the seals to follow vertically moving prey, was positively related to seal mass, indicating that small mass restricted foraging ability. The shorter dive durations of the smaller seals inferred that they had shallower dive depths in which to search for prey, thus restricting foraging ability. Although foraging ability was restricted by size, foraging success was found to be inversely related to mass, the smaller seals gaining a higher proportion of blubber than larger seals during their foraging trips. Thus, despite smaller seals being restricted to shallower depths and shorter durations, their foraging success was not affected.
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Jaeger Drehmer, C., J. Ferigolo and E. S. Borsato (1998). Occurrence of Mirounga leonina Linnaeus (Pinnipedia, Phocidae) from southernmost Brazil: injury and pathologies. Revista Brasileira de Zoologia 15(4): 1061-1068.
A male specimen Mirounga leonina Linnaeus, 1758 age estimated between 7-8 years old, collected at Santa Vitoria do Palmar, Rio Grande do Sul State, southernmost Brazil (32 degree 44'S and, 53 degree 22'W) is presented. All the skeleton was recovered except the rostral region. It shows an advanced osteomyelitis in the left dentary, extending from the synfisis until the middle portion of the body; as well as Scheuermann disease at lumbar vertebrae. Such diseases could explain its presence at that locality, where it was shot. The bullet was recovered from the rostrum, and might be responsible for death. This is the first virtually complete skeleton of M. leonina recovered from Brazilian coast.
Johnson, D. W. (1990). A southern elephant seal (Mirounga leonina Linn.) in the northern hemisphere (Sultanate of Oman). Marine Mammal Science 6(3): 242-243.
Jones, E. (1981). Age in relation to breeding status of the male souther elephant seal, Mirounga leonina (L.), at Macquarie Island. Australian Wildlife Research 8(2): 327-334.
Records of the breeding status of known-age male southern elephant seals at Macquarie I. were kept during five breeding seasons between 1969 and 1976. The seven status categories used were: beachmaster, secure assistant, medium harem owner, insecure assistant, small harem owner, attending bachelor, avoiding bachelor. There was a progressive increase in breeding status with age; none younger than 10 y old bred; 16% of 10-y-olds and 55% of 12-y-olds did so; none younger than 12 y old attained secure assistant status. At the earliest, beachmaster status may be attained at 14 y old, but no beachmasters of known age were recorded. Problems associated with the precise definition of status categories are discussed.
Jonker, F. C. and M. N. Bester (1994). The diving behaviour of adult southern elephant seal, Mirounga leonina, cows from Marion Island. South African Journal of Antarctic Research 24( 1-2): 75- 93.
The diving patterns of eight adult southern elephant seal, Mirounga leonina, cows (seven post-breeding and one post-moulting) from subantarctic Marion Island were recorded during the pelagic phase of their annual cycle, using geolocating time-depth recorders attached to the seals. A total of 28 948 dives have been categorised into seven distinct types representing transit, exploratory and foraging dives. No benthic foraging dives were recorded and all but one cow showed a marked diel variation in dive depth, dives being deeper during the day (by 30 to 300 m) than during the night. Mean ( plus or minus SE) dive depth ranged from 406 plus or minus 157 m to 585 plus or minus 226 m and mean dive duration from 19,08 plus or minus 5,77 min to 33,41 plus or minus 14,62 min, the deepest and longest dives being 1 444 m and 113 min respectively. Dive depth and duration were positively corelated and unimodal in their frequency distribution, and two cows had secondary modes at 800 to 900 m and 40 to 44 min respectively. Post-dive surface intervals ranged from 2,03 plus or minus 1,64 min to 4,99 plus or minus 53,34 min between individuals and were unrelated to dive depths and durations of previous, as were extended surface intervals (>10 min) which were more frequent at night during the day. Extended surface intervals were also more common during long journeys at sea and were probably associated with successfully foraging. The frequency of occurrence and the bottom times of foraging dives varied with the season, the highest frequency of occurrence and longest bottom times being recorded during the post-moulting (winter) period. It is postulated that the seasonal and individual variation in the diving behaviour of the southern elephant seal cows are related to their geographic locations and the abundance and behaviour of their prey.
Jonker, F. C. and M. N. Bester (1998). Seasonal movements and foraging areas of adult southern female elephant seals, Mirounga leonina, from Marion Island. Antarctic Science 10(1): 21-30.
Seasonal movements and foraging areas of postbreeding and postmoulting adult female southern elephant seals from Marion I. were studied using Geolocation Time-depth Recorders. Movements were classified into 3 phases: an outbound transit phase, distant foraging phase, and an inbound transit phase. The longest residence time of postbreeding females during their foraging migrations was in areas at the outer edge of their feeding range both to the north and south of the island. Postmoulting females travelled further afield, including the antarctic continental shelf. This study provides additional information on the putative function of dive types in relation to the movement phases of female elephant seals from Marion I. The relative frequency of assumed 'foraging', 'exploratory' and 'transit' dive types, as well as the duration and location of the different phases of movement suggest two seasonal foraging strategies.
Jurachno, M. V. and V. N. Maltsev (1999). Redescription of Baylisiella tecta (Cestoda: Pseudophyllidea) and establishing of new family and new superfamily. Parazitologiya 33(2): 104-112.
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Kajiwara, N., K. Kannan, M. Muraoka, M. Watanabe, S. Takahashi, F. Gulland, H. Olsen, A. L. Blankenship, P. D. Jones, S. Tanabe and J. P. Giesy (2001). Organochlorine pesticides, polychlorinated biphenyls, and butyltin compounds in blubber and livers of stranded California sea lions, elephant seals, and harbor seals from coastal California, USA. Archives of Environmental Contamination and Toxicology 41(1): 90-99.
Concentrations of polychlorinated biphenyls (PCBs), DDTs (p,p'-DDE, p,p'-DDD, p,p'-DDT), chlordanes (CHLs; cis-chlordane, cis-nonachlor, trans-nonachlor, and oxychlordane), hexachlorocyclohexane isomers (HCHs), hexachlorobenzene (HCB), tris(4-chlorophenyl)methane (TCPMe), tris(4-chlorophenyl)methanol (TCPMOH), and mono- (MBT), di-(DBT), and tri-butyltin (TBT) were determined in blubber and livers of 15 California sea lions (Zalophus californianus), 6 northern elephant seals (Mirounga augustirostris), and 10 harbor seals (Phoca vitulina) found stranded along the coasts of California, USA, during 1991-1997. Among the organochlorines analyzed, DDTs were predominant, followed in decreasing order by PCBs, CHLs, TCPMe, TCPMOH, HCHs, and HCB. The greatest concentrations of organochlorines were found in California sea lions. The highest DDT and PCB concentrations found in the blubber of California sea lions were 2,900 and 1,300 microg/g, lipid weight, respectively. Concentrations of TCPMe and TCPMOH in California sea lions were correlated significantly with DDT concentrations. Concentration ratios of various organochlorines in harbor seal livers were different from those in California sea lions and elephant seals, which suggested that the sources of exposure of harbor seals to organochlorines were different from those in the other two species. Concentrations of butyltin compounds in livers of pinniped species ranged from 2 to 99 ng/g, wet weight, which were less than those observed in cetaceans and in California sea otters.
Kastak, D. and R. J. Schusterman (1995). Comparative aspects of low frequency hearing in the northern elephant seal. World Marine Mammal Science Conference Orlando, Florida, Lawrence, KS, Society for Marine Mammalogy.
Kastak, D. A. (1996). Comparative aspects of hearing in Pinnipeds. Department of Biology. Santa Cruz, California, University of California.
Kastak, D. and R. J. Schusterman (1998). Low-frequency amphibious hearing in pinnipeds: methods, measurements, noise, and ecology. Journal of the Acoustical Society of America 103(4): 2216-2228.
Aerial low-frequency (100–6400 Hz) hearing thresholds were obtained for one California sea lion (Zalophus californianus), one harbor seal (Phoca vitulina), and one northern elephant seal (Mirounga angustirostris). Underwater thresholds over a similar frequency range (75–6300 or 6400 Hz) were obtained for these three animals in addition to another California sea lion. Such data are critical, not only for understanding mechanisms about amphibious hearing and relating them to pinniped ecology and evolution, but also for identifying species at risk to man-made noise in the marine environment. Under water, the elephant seal was most sensitive, followed by the harbor seal and the sea lions. In air, the harbor seal was most sensitive, followed by the older of the two sea lions and the elephant seal. The following trends emerged from comparisons of each subject’s aerial and underwater thresholds: (a) the sea lion, although possessing some aquatic modifications, is adapted to hear best in air;(b) the harbor seal hears almost equally well in air and under water; and (c) the elephant seal’s auditory system is adapted for underwater functioning at the expense of aerial hearing sensitivity. These differences became evident only when aerial and underwater thresholds were compared with respect to sound pressure rather than intensity. When such biologically relevant comparisons are made, differences in auditory sensitivity can be shown to relate directly to ecology and life history.
Kastak, D. and R. J. Schusterman (1998). Pinniped hearing: amphibious adaptations and the effects of noise. World Marine Mammal Science Conference Monaco, Lawrence, KS, Society for Marine Mammalogy.
Kastak, D. and R. Schusterman (1999). In-air and underwater hearing sensitivity of a northern elephant seal (Mirounga angustirostris). Canadian Journal of Zoology 77(11): 1751-1758.
In-air and underwater sound detection thresholds were obtained for a female northern elephant seal (Mirounga angustirostris). Hearing sensitivity in air was generally poor, but was best for frequencies between 3.2 and 15 kHz, and showed greatest sensitivity at 6.3 kHz (43 dB re: 20 µPa). The upper frequency limit in air was approximately 20 kHz. The underwater audiogram is similar to those obtained from other phocids in that sensitivity was best between 3.2 and 45 kHz, with greatest sensitivity at 6.4 kHz (58 dB re: 1 µPa) and an upper frequency cutoff of approximately 55 kHz. The elephant seal was more sensitive to low frequencies (<1 kHz) than other pinnipeds tested. Thresholds obtained in water were lower than those obtained in air (19 dB in terms of sound pressure, 52 dB in terms of sound intensity), indicating that the elephant seal is adapted for underwater hearing. The outer and middle ears of the elephant seal are modified relative to those of other phocids. These modifications are probably needed to cope with extreme static pressures related to deep diving, and are likely to confer relatively good auditory sensitivity under water.
Kastak, D., R. J. Schusterman, B. L. Southall and C. J. Reichmuth (1999). Underwater temporary threshold shift induced by octave-band noise in three species of pinniped. Journal of the Acoustical Society of America 106(2): 1142-1148.
Pure-tone sound detection thresholds were obtained in water for one harbor seal (Phoca vitulina), two California sea lions (Zalophus californianus), and one northern elephant seal (Mirounga angustirostris) before and immediately following exposure to octave-band noise. Additional thresholds were obtained following a 24-h recovery period. Test frequencies ranged from 100 Hz to 2000 Hz and octave-band exposure levels were approximately 60-75 dB SL (sensation level at center frequency). Each subject was trained to dive into a noise field and remain stationed underwater during a noise-exposure period that lasted a total of 20-22 min. Following exposure, three of the subjects showed threshold shifts averaging 4.8 dB (Phoca), 4.9 dB (Zalophus), and 4.6 dB (Mirounga). Recovery to baseline threshold levels was observed in test sessions conducted within 24 h of noise exposure. Control sessions in which the subjects completed a simulated noise exposure produced shifts that were significantly smaller than those observed following noise exposure. These results indicate that noise of moderate intensity and duration is sufficient to induce TTS under water in these pinniped species.
Kastelein, R. A., J. Kershaw and P. R. Wiepkema (1991). The food consumption of southern elephant seals (Mirounga leonina ). Aquat. Mamm. 17(2): 76-87.
This study concerns the food consumption of 1 male and 2 female southern elephant seals at Marineland, Antibes, France. The females' food intake increased for about 3 years after which it stabilized at around 3400 kg/year. The male's annual intake reached a peak of 11.600 kg during his 6th year after which it dropped and stabilized at around 8000 kg/year. Although the animals were allowed to eat as much as they wanted, the food intake fluctuated seasonally. The annual periods with a low food intake correspond with the breeding (after maturity) and moulting seasons in both sexes. After each moult, the animals increased their food consumption to replenish their energy reserves. In relation to their body weight, the animals ate less than the rough estimate normally used for animals in the wild. This could be because, at Marineland, the air and water temperatures are higher, the diet has a higher energy content, and less energy is needed for feeding than in the wild.
Keith, E. O. and C. L. Ortiz (1989). Glucose kinetics in neonatal elephant seals during postweaning aphagia. Marine Mammal Science 5( 2): 99-115.
Northern elephant seal (Mirounga angustirostris ) pups undergo extended periods of terrestrial aphagia after weaning and exhibit a paradoxical fasting hyperglycemia. To investigate the details of glucose metabolism during this period, reversible and irreversible radiotracers were used to determine the body mass of glucose, and rates of glucose turnover, recycling, and oxidation in fasting seal pups. About 20% of the glucose pool was removed from the blood per hour, yielding a turnover time in the vascular space of about five hours. Most glucose removed from the blood was returned to the blood by recycling. Such recycling may contribute to mechanisms which prolong survival during fasting, such as high rates of triacyclglycerol turnover, synthesis of new protein pools, low ketone levels, and the Cori cycle which is important during diving.
Kenny, R. (1979). Breathing and heart rates of the southern elephant seal, Mirounga leonina (L.).
Kenny, R. P. (1979). Bibliography of the southern elephant seal, Mirounga leonina (L.).
King, J. E. (1966). Relationship of the hooded and elephant seals (genera Cystophora and Mirounga). Journal of Zoology London 148: 385-398.
King, J. E., A. K. Fukuyama, S. J. Krenn and A. C. Setran (1989). New mainland haul-out site for the northern elephant seal, Mirounga angustirostris, in central California.
This note documents the use of a new haul-out site by the northern elephant seal, Mirounga angustirostris Gill. This site is on the mainland of the central California coast next to a man-made breakwater which protects the water intake structure for an electric-generating power plant. We describe the features of this new site and include some changes in abundances over time, although additional information is currently being gathered.
King, J. K. and M. M. Bryden (1992). Mirounga leonina. Mammalian Species 391: 1-8.
King, D. P., J. L. Sanders, C. T. Nomura, R. A. Stoddard, C. L. Ortiz and S. W. Evans (1998). Ontogeny of humoral immunity in northern elephant seal (Mirounga angustirostris) neonates. Comparative Biochemistry and Physiology B Biochemistry & Molecular Biology 121B(4): 363-368.
Kinuta, T. and T. Iwawoto (1979). A case of localized papillary mesothelioma of the pleura in the southern elephant seal, Mirounga leonina.
Kirk, G. (1999). [The protection of the northern elephant seal Mirounga angustirostris in the North Pacific.]. Saugetierkundliche Mitteilungen 44(3): 113-114.
Kirk, G. (1999). [Nature protection and politics - country comparisons. Part 1. Mexico.]. Bombina 21(2): 12-13.
Kirkman, S. P., M. N. Bester, P. A. Pistorius, G. J. G. Hofmeyr, R. Owen and S. Mecenero (2001). Participation in the winter haulout by southern elephant seals (Mirounga leonina). Antarctic Science 13(4): 380-384.
Southern elephant seals haulout on land to moult, breed and for a third, unknown reason, which we refer to as the winter haulout. We used long-term mark-recapture data to estimate participation levels in the winter haulout by southern elephant seals at Marion Island. There was no evidence that participation levels varied between cohorts or between years. Participation differed between sexes, with males being more likely to haulout in winter, except in the first year of life where participation was equal. Within each sex, both age and reproductive status influenced participation, but age seemed to be the most influential determinant. Generally, immature male individuals hauled out year after year in winter. The results did not allow speculation as to the purpose(s) of the winter haulout.
Kirkman, S. P., G. J. G. Hofmeyer, M. N. Bester and K. Isaksen (2001). Counts of southern elephant seals, Mirounga leonina, at Bouvet Island. Polar Biology 24: 62-65.
Southern elephant seals were counted and classified into subjective sex-age classes on a weekly basis during expeditions to Bouvet Island in the austral summers of 1996/1997 and 1998/1999. The expeditions coincided with the moulting period of elephant seals aged one year and older. The presence of weaned pups at the principal haulout site, Nyroysa/Westwindstranda, during the latter expedition, indicates that breeding took place here during 1998. Elephant seal counts from previous expeditions are summarised.
Kiyota, M., N. Baba and M. Mouri (1992). Occurrence of an elephant seal in Japan. Marine Mammal Science 8( 4): 433.
On 21 November 1989, a northern elephant seal, Mirounga angustirostris , was observed on a sandy beach on Niijima Island (34 degree 20'N, 139 degree 15'E), one of the Izu Islands, 40 km off the Pacific coast of Japan. The seal was a young male, 2.3 m long (total length from nose to tip of hind flippers) and weighed 194 kg. Dr. B. Stewart of Hubbs-Sea World Research Institute confirmed our identification from photos and judged the seal to be approximately 22 mo old from its length. Northern elephant seals breed from central Baja California to the Point Reyes Peninsula near San Francisco, California. Until now, the westernmost published record for northern elephant seals was at Midway Island (28 degree 15'N, 177 degree 23'W). Niijima lies 5,000 km west of Midway and 11,000 km from California. We speculate that the North Equatorial Current might have carried the animal as far west as the Japanese coast. Recent studies demonstrate that adult male and female elephant seals migrate extensively from rookeries in California; adult males to the Aleutian islands and females to Central Pacific waters.
Kiyota, M. and N. Baba (1999). Records of northern fur seals and other pinnipeds stranded or taken incidentally by coastal fishery in Japan, 1977-1998. Bulletin of the National Research Institute of Far Seas Fisheries 36: 9-16.
Klevezal, G. A. and B. S. Stewart (1994). Patterns and calibration of layering in tooth cementum of female northern elephant seals, Mirounga angustirostris. Journal of Mammalogy 75(2): 483-487.
Klimley, A. P. (1994). The predatory behavior of the white shark. American Scientist 82(2): 122-133.
Klobes, U., W. Vetter and B. Luckas (1999). Levels of eight toxaphene congeners in different tissues of marine organisms.
Klos, H. G. (1979). Hand-rearing a southern elephant seal Mirounga leonina at West Berlin Zoo.
Kohin, S. (1998). Respiratory physiology of northern elephant seal pups: adaptations for hypoxia, hypercapnia, and hypometabolism. Department of Biology. Santa Cruz, California, University of California.
Kretzmann, M. B., D. P. Costa and B. J. Le Boeuf (1993). Maternal energy investment in elephant seal pups: evidence for sexual equality ? American Naturalist 141(3): 466-480.
Labeled water methodology was used to qunatify maternal energy investment in northern elephant seals (Mirounga angustirostris) pups. Pup milk intake, field metabolic rate, mass change, and body composition were monitored during the nursing period and throughout the postweaning fast. Maternal investment did not vary significantly as a function of pup sex. There was no evidences for sex differences in growth rate or milk intake rat, and mean metabolic rate of suckling pups did not differ significantly between the sexes. Males and females appeared to be in similar condition at the end of the postweaning fast, just prior to their first trip to sea. Some male pups may attain grater size relative to females without additional cost to their mothers. These data do not provide evidences to reject R. A. Fisher theory of equal investment in the sexes
Krockenberger, M. B. and M. M. Bryden (1993). Energy intake of immature southern elephant seals, Mirounga leonina (Carnivora: Phocidae). Australian Journal of Zoology 41(6): 589-597.
The authors report the mass of food and energy consumed by, and growth of, three immature southern elephant seals from 14 months to 3 years old, at Taronga Zoo, Sydney. The seals were fed four species of fish and one squid genus. There was no consistent or seasonal pattern of variation among the different dietary components, and mean figures for fat, protein, water and energy were used in calculations of dietary consumption by the seals. The mean energy density of the food was 8.65 kJ/g. The growth rate of the three seals was at the high end of the range for wild southern elephant seals. As in natural populations, growth was positive for most months of the year, but negative from November to January, when fasting, haulout and moulting occur in wild elephant seals of similar age. There was no evidence of fluctuations in energy intake as a result of seasonal variation of temperature or other weather effects. The three animals spent 30% of their time active and 70% at rest. This contrasted with the wild population, in which immature animals of similar age spend more than 70% of their time active and less than 30% at rest. The gross energy intake of the cohort of young, growing elephant seals at Macquarie Island was estimated to be of the order of 1570 x 10 super(6) MJ per year.
Krockenberger, M. B. and M. M. Bryden (1994). Rate of passage of digesta through the alimentary tract of southern elephant seals (Mirounga leonina) (Carnivora: Phocidae). Journal of Zoology London 234( 2): 229- 237.
The inert markers chromium-EDTA (liquid phase marker) and ytterbium nitrate (solid phase marker) were added to the food of three southern elephant seals (Mirounga leonina) in Taronga Zoo, Sydney, in a series of nine trials. The enclosures were checked at 15 to 30 minute intervals for up to 60 hours after dosing, and all faeces voided on land were collected (91 samples). Marker concentrations in faecal dry matter were determined and mean retention times calculated from the concentration-time curves. The faeces were soft to semiliquid, with mean water content of 58% (range 24-80%). The marker concentration curves indicated a rapid rate of food transit through the gastro-intestinal tract in elephant seals compared with other carnivores. The mean time between dosing and first recovery of marker (Initial Recovery Time) was nine hours. This was significantly longer than the figure of 4.8 hours for northern elephant seals reported previously, and possible reasons for the differences are discussed. Mean Retention Time, a better index of rate of passage of ingesta, was 13 hours for the three southern elephant seals. This compares with times of 22 hours for the dog, 15 hours for the raccoon, and 13 hours for the cat, all carnivores with much shorter gastrointestinal tracts, both absolutely and relative to body size, than the southern elephant seal. It is suggested that the very long small intestine may be an adaptation to foraging at depth, combined with long periods of submergence and the need to ingest large amounts of food when the animal is at sea continuously for weeks or months.
Krzeminski, W. (1981). Southern elephant seal (Mirounga leonina L.) of Admiralty Bay (King George Island, South Shetland Islands). Polish polar research 2(1/2): 143-152.
Studies on southern elephant seal were carried out in Admiralty Bay in summer 1978/1979. In the whole region most (964) elephant seals were noticed on 5 Jan. 1979. The biggest nonbreeding colonies were observed in the mouth of the bay. In December the males made up 74% of the whole population; their number decreased to 17% in February. Most individuals belonged to the IV age class (6-9 years old). Introductory observation of 24 h activity indicates four peaks of activity in the groups observed on the coast. The type of weather influences the activity of these groups and the frequency of descending to the sea.
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La Linn, M., J. Gardner, D. Warrilow, G. A. Darnell, C. R. McMahon, I. Field, A. D. Hyatt, R. W. Slade and A. Suhrbier (2001). Arbovirus of marine mammals: a new alphavirus isolated from the elephant seal louse, Lepidophthirus macrorhini. J Virol 75(9): 4103-9.
A novel alphavirus was isolated from the louse Lepidophthirus macrorhini, collected from southern elephant seals, Mirounga leonina, on Macquarie Island, Australia. The virus displayed classic alphavirus ultrastructure and appeared to be serologically different from known Australasian alphaviruses. Nearly all Macquarie Island elephant seals tested had neutralizing antibodies against the virus, but no virus-associated pathology has been identified. Antarctic Division personnel who have worked extensively with elephant seals showed no serological evidence of exposure to the virus. Sequence analysis illustrated that the southern elephant seal (SES) virus segregates with the Semliki Forest group of Australasian alphaviruses. Phylogenetic analysis of known alphaviruses suggests that alphaviruses might be grouped according to their enzootic vertebrate host class. The SES virus represents the first arbovirus of marine mammals and illustrates that alphaviruses can inhabit Antarctica and that alphaviruses can be transmitted by lice.
Lane, R. A. B., R. J. H. Morris and J. W. Sheedy (1972). Haematological study of the southern elephant seal, Mirounga leonina (Linn.). Comparative Biochemistry and Physiology 42(4A): 841-850.
In studies carried out at Macquarie I. fifty-two southern elephant seals were bled and standard hematological parameters measured, and compared to those of other pinnipeds. The red blood cell diameters and mean corpuscular volumes were found to be large while the red blood cell counts were low. The measured whole blood iron and derived iron (from the hemoglobin concentration) correlated closely. As reported in other pinnipeds, the packed cell volume and the mean corpuscular hemoglobin concentration were higher than in other mammals.
Larsen, R. S., M. Haulena, C. B. Grindem and F. M. Gulland (2002). Blood values of juvenile northern elephant seals (Mirounga angustirostris) obtained using a portable clinical analyzer. Vet Clin Pathol 31(3): 106-10.
BACKGROUND: Sick, injured, or orphaned juvenile northern elephant seals (Mirounga angustisrostris) treated at rehabilitation centers frequently present with abnormalities in blood sodium, potassium, chloride, BUN, and glucose concentrations, and HCT. These abnormalities could be detected rapidly using a portable blood analyzer, but results with this analysis method do not necessarily equate with those obtained using other techniques. OBJECTIVE: The objective of this study was to better assess the clinical relevance of values obtained from a portable analyzer and to compare the results with values obtained using more common methods of analysis. METHODS: Heparinized whole blood samples were collected from 20 rehabilitated juvenile northern elephant seals. A portable clinical analyzer (i-STAT, i-STAT Corp, East Windsor, NJ, USA) was used to establish baseline values. Serum biochemical values were obtained using an automated chemical analyzer (Olympus AU5200, Olympus America, Melville, NY, USA). HCT was determined using EDTA whole blood and a cell counter. RESULTS: Using the portable analyzer, mean (minimum-maximum) values were obtained for sodium, 143 (132-146) mmol/L; potassium, 4.4 (3.9-5.8) mmol/L; chloride, 106 (101-109) mmol/L; BUN, 1.8 (1.1-2.4) mmol/L; glucose, 7.55 (5.99-8.49) mmol/L; and HCT, 0.55 (0.52-0.61) L/L. Average differences between methods were small for potassium (-0.45 mmol/L), BUN (0.1 mmol/L), and HCT (0.037 L/L) but were large for sodium (-6.8 mmol/L), chloride (-6.4 mmol/L), and glucose (-0.56 mmol/L). CONCLUSIONS: These results suggest that the i-STAT portable analyzer could be useful for clinically assessing juvenile elephant seals. However, when making medical decisions, the clinician should be aware of differences associated with various analyzers and sample types.
Laws, R. M. (1953 b). The elephant seal (Mirounga leonina Linn.). I. Growth and age. Scientific Reports of the Falkland Islands Dependencies Survey 8: 1-62.
Laws, R. M. (1956 a). The elephant seal (Mirounga leonina Linn.). II. General, social, and reproductive behaviour. Scient. Rep. Falkland Is. Depend. Surv. 13: 1-88.
Laws, R. M. (1956 b). The elephant seal (Mirounga leonina Linn.). III. The physiology of reproduction. Scient. Rep. Falkland Is. Depend. Surv. 15: 1-66.
Laws, R. M. (1960 a). The Southern Elephant Seal (Mirounga leonina Linn.) at South Georgia. Norsk Hvalf. Tid. 10: 466-476.
Laws, R. M. (1960 b). The Southern Elephant Seal (Mirounga leonina Linn.) at South Georgia. Norsk Hvalf. Tid. 11: 520-542.
Laws, R. M. (1994). History and present status of southern elephant seal populations. Elephant seals. Population ecology, behavior and physiology. B. J. L. Boeuf and R. M. Laws. Berkeley (CA), University of California Press: 49-65.
Le Boeuf, B. J. and R. S. Peterson (1969 a). Social status and mating activity in elephant seals. Science 163: 91-93.
Le Boeuf, B. J. and R. S. Peterson (1969 b). Dialects in elephant seals. Science 166: 1654-1656.
Le Boeuf, B. J. (1972). Sexual behaviour of the northern elephant seal Mirounga angustirostris. Behaviour 41: 1-26.
Le Boeuf, B. J., R. J. Whiting and R. F. Gantt (1972). Perinatal behavior of Northern Elephant Seal females and their young. Behaviour 43: 121-156.
Le Boeuf, B. J. (1974). Male-male competition and reproductive success in elephant seals. American Zoologist 14: 163-176.
Male-male compelition and reproductive success of northern elephant seals, Mirounga angustirostris, was studied for six consecutive breeding seasons at Ano Nuevo Island, California. The conclusions were as follows: (i) Less than one third of the males in residence copulate during a breeding reason.A few males are responsible for the majority of copulations. (ii) The number and age of males copulating varied with: (a) harem localion and topography, (b) the number of estrous females in the harem, and (c) the number of males competing for females. (iii) Copulation frequency is related directly to success in male-male competition, i e, social rank. (iv) The same individuals may dominate breeding for three consecutive breeding seasons. (v) Successful male die within a year or two after their reproductive peak. (vi) The reproductive success of most males is nil or low because many die before reaching breeding age and some of those that reach maturity are prevented from mating by the highest ranking males. (vii) Individual strategie6s have important consequences for reproductive success. (viii) Male male competition is a major cause of pup mortality prior to weaning. The potential reproductive success of males is much greater than that of females. Changes in colony number and composition affect the reproductive success of males as well as females.
Le Boeuf, B. J., D. G. Ainley and T. J. Lewis (1974). Elephant seals on the Farallones: population structure of an incipient breeding colony. Journal of Mammalogy 55(2): 370-385.
Le Boeuf, B. J. and L. F. Petrinovich (1974 a). Elephant seals: interspecific comparisons of vocal and reproductive behavior. Mammalia 38(1): 16-32.
Le Boeuf, B. J. and L. F. Petrinovich (1974 b). Dialects of northern elephant seals, Mirounga angustirostris: origin and reliability. Animal Behaviour 22: 656-663.
Le Boeuf, B. J. and K. T. Briggs (1977). The cost of living in a seal harem. Mammalia 41(2): 167-195.
Individual seals benefit from breeding in groups but they also incur costs because of conflicts of interest with each other. The relative cost/benefit relationship to females can be measured in terms of reproductive success and pup mortality is one indicator of costs. The pup mortality rate on Ano Nuevo Island ranged from 13-26% of pups born during the years 1968 to 1976. The major proximal cause of pup mortality was due to a syndrome of Trauma-Starvation which began with mother-pup separation and ended with starvation or injury. Two sources of trama accounted for most mortalities: (1) orphans were bitten when they attempted to suckle alien females. These pups had fractured skulls and jaws and extensive external lacerations at necropsy. (2) Both orphans and filials were crushed by breeding bulls and died from internal hemorrhage and ruptured organs. At last 60% of the mortalities each year resulted from injuries inflicted by adult seals. Three classes of variables contributed to fluctuations in pup mortality: (1) the level of female aggression in the harem, (2) the number, distribution and density of females in the harem, and (3) storms which flooded the harem at peak season. As the colony grew in size, harems took up a greater portion of the beach and breeding females and their pups were vulnerable to winter storms. Storms killed pups directly and caused momentary increases in female density which increased the level of female aggression and facilitated mother-pup separation and pup injury. Pup mortality was highest when storms flooded large harems that covered the entire beach. These costs resemble the pup mortality rates found in other pinnipeds where group living gives rise to conflicts between individuals, e.g., the grey seal. Elephant seal females can minimize their costs by adopting several strategies. The benefits of social breeding are discussed, particularly the possibility of breeding with the most fit male.
Le Boeuf, B. J. and B. R. Mate (1978). Elephant seals colonize additional Mexican and Californian islands. Journal of Mammalogy 59(3): 621-622.
Le Boeuf, B. J. (1981). The elephant seal. Problems in management of locally abundant wild mammals. P. A. H. Jewell, S.: 291-301.
Le Boeuf, B. J., M. Riedman and R. S. Keyes (1982). White shark predation on pinnipeds in California coastal waters. U S Fish and Wildlife Service Fishery Bulletin 80(4): 891-895.
Le Boeuf, B. J. and R. S. Condit (1983). The high cost of living on the beach. Pacific Discovery 36(3): 12-14.
When huge waves generated by violent storms battered the Pacific coast repeatedly during the winter of 1983, hundreds of elephant seals died in the greatest tragedy to befall these animals since their near extermination by commercial hunters in the last century. Besides killing pups directly, severe winter storms increase crowding in harems, heighten aggression between females, and cause mothers and pups to be separated. Pup mortality on Ano Nuevo Island in 1983 was an extraordinary 70 percent of those born-683 pups died out of 975 produced. For comparison, the pup mortality rate in previous non-storm years was less than 10 percent of pups born in uncrowded harems and less than 35 percent in crowded harems.
Le Boeuf, B. J., J. E. McCosker and J. Hewitt (1987 a). Crater wounds on Northern elephant seal: the cookiecutter shark strikes again. U S Fish and Wildlife Service Fishery Bulletin 85(2): 387-392.
Le Boeuf, B. J., D. P. Costa, A. C. Huntley and S. D. Feldkamp (1988). Continuous, deep diving in female Northern elephant seals, Mirounga angustirostris. Canadian Journal of Zoology 66: 446-458.
Le Boeuf, B. J., Y. Naito, A. C. Huntley and T. Asaga (1988). Prolonged, continuous, deep diving by Northern elephant seals. Canadian Journal of Zoology 67: 2514-2519.
Le Boeuf, B. J. and J. Reiter (1988). Lifetime reproductive success in northern elephant seals. Reproductive success. Studies of individual variation in contrasting breeding systems. T. H. Clutton-Brock. Chicago, University of Chicago Press. 1: 344-362.
Le Boeuf, B. J. (1989). Incredible diving machines. Natural History 2/89: 35-40.
Le Boeuf, B. J., R. Condit and J. Reiter (1989). Parental investment and the secondary sex ratio in Northern elephant seals. Behavioral Ecology and Sociobiology 25: 109-117.
Data on northern elephant seals, Mirounga angustirostris, bearing on sex ratio theory were collected at Ano Nuevo, California, and other Californian and Mexican Islands, during the period 1967 to 1988. The mass of males exceeded that of females by 7-8% at birth and at weaning. The sex ratio was biased to males at birth (51.2%) and was near unity at weaning (49.6% males). The sex ratio did not vary as a function of maternal age or maternal mass except in 6-year-old females, who produced significantly more males. Although sons cost more to rear in energetic terms than daughters, and mothers were more successful weaning the latter, the sex of the pup reared exerted no significant effect on the mother's reproductive performance the following year or on her subsequent survival. These data suggest that parents invest equally in sons and daughters when investment is measured in terms of future reproduction (Fisher 1930) and provide no support for the theory of adaptive shifts in sex ratio (Trivers and Willard 1973). The small sex difference in mass due to maternal effort reflects the fact that females fast during lactation and all energy transferred is from limited body stores. Because of these circumstances, selection for superior condition at the end of the period of parental investment may act more strongly on pups, who have the opportunity to steal milk, than on their mothers.
Le Boeuf, B. J. and S. Mesnick (1990). Sexual behavior of male northern elephant seals: I. Lethal injuries to adult females. Behaviour 116(1-2): 143-162.
Adult female mortality of northern elephant seals, Mirounga angustirostris , was monitored daily throughout the breeding season and weekly during the non-breeding season at Ano Nuevo, California, during the period 1968 to 1987. Female deaths on the rookery were rare; only 17 female deaths were recorded over the 20 year period. Cause of death could not be estimated in three cases because of advanced decomposition, one female died from an accident, and two others had no apparent trauma. The majority of deaths (11) were caused by traumatic injuries inflicted by males during mating attempts as the females departed harems for the sea at the end of lactation. Mortalities caused by males were distributed across a broad age range. Based on the observed incidence of female mortality in relation to females present on the rookery, the probability of a female being killed by a male during the breeding season is about one in a thousand. Females are expected to evolve adaptations to reduce injurious encounters with males.
Le Boeuf, B. J. and J. Reitter (1991). Biological effects associated with El Nino southern oscillation, 1982-83, on northern elephant seals breeding at Ano Nuevo, California.
Le Boeuf, B. J., Y. Naito, T. Asaga, D. Crocker and D. P. Costa (1992). Swim speed in a female northern elephant seal: Metabolic and foraging implications. Canadian Journal of Zoology 70( 4): 786- 795.
The swim speed and dive pattern of an 8-year-old female northern elephant seal (Mirounga angustirostris ) were recorded during the postlactation period at sea. Mean swim speeds calculated as a function of time and distance ranged from 0.91 to 1.66 m/s. Mean descent velocities were 27% greater than ascent velocities and velocities at depth. Minimum and maximum speeds ranged from 0.4 to 3.0 m/s for most segments of all dives. There was no surface swimming. Angles of descent were less steep (30-56 degree ) than angles of ascent (52-82 degree ). Mean total horizontal distance traveled per dive ranged from 0.6 to 1.3 km, depending on dive type. From the above data and related information, each of four dive types, which accounted for the majority of dives in the record, were hypothesized to have one of the following principal functions: transit, foraging (pelagic and benthic), and process (serving rest, food processing, or anaerobic metabolite clearance).
Le Boeuf, B. J. (1994). Variation in the diving pattern of northern elephant seals with age, mass, sex, and reproductive condition. Le Boeuf: opulation ecology, behavior, and physiology University of California Press Berkeley, Los Angeles etc 1994 i-xviii, 1-414 Chapter pagination 237-252.
Le Boeuf, B. J., P. Morris and J. Reiter (1994). Juvenile survivorship of Northern elephant seals. Elephant seals. Population ecology, behavior and physiology. B. J. Le_Boeuf and R. M. Laws. Berkeley (CA), University of California Press: 121-136.
Le Boeuf, B. J. and R. H. Laws (1994 a). Elephant seals. Population ecology, behavior and physiology. Berkeley, CA, University of California Press.
Le Boeuf, B. J. and R. H. Laws (1994 b). Elephant seals: an introduction to the genus. Elephant seals. Population ecology, behavior and physiology. B. J. L. B. R. M. Laws. Berkeley , CA, University of California Press: 1-26.
Le Boeuf, B. J. and D. E. Crocker (1996). Diving behavior of elephant seals: implications for predator avoidance. Klimley, A Peter; Ainley: i-xi, 1-517 Chapter pagination 193-205.
Le Boeuf, B. J., P. A. Morris, S. B. Blackwell, D. E. Crocker and D. P. Costa (1996). Diving behavior of juvenile northern elephant seals. Canadian Journal of Zoology 74(9): 1632-1644.
We describe and review the development of the diving and foraging pattern of northern elephant seals, Mirounga angustirostris, during migrations over the first 2 years of life. The diving pattern and migratory tracks of 23 juveniles, 9-27 months of age, from Ano Nuevo and Piedras Blancas, California, were recorded with attached time-depth recorders and Argos satellite tags. The seals exhibited a general diving pattern like that of adults, diving deep (373 +/- 77 m per dive (mean +/- SD)), long (15.2 +/- 2.6 min per dive), and continuously (88.7 +/- 2.7% of the time submerged while at sea). Level of performance increased with age and experience up to 2 years of age, the end of the fourth migration, when modal diving performance was equal to that of adults. Juveniles migrated north to the waters west of Oregon, Washington, and British Columbia, moving more slowly and not as far as adults. By the third trip to sea, males began to exhibit more flat-bottomed dives than females, a sex difference observed in adults, suggesting that males supplement a diet of pelagic organisms with benthic prey. These data and related observations of elephant seals suggest that the greatest physiological changes enabling an animal to dive occur near the rookery following weaning, before the first trip to sea; transition to a pelagic existence is difficult, as reflected by high mortality during the first migration; improvement of diving skills continues up to 2 years of age; and sex differences in foraging behavior and foraging location, similar to those seen in adults, are evident before the seals reach 2 years of age.
Le Boeuf, B. J., D. E. Crocker, D. P. Costa, S. B. Blackwell, P. M. Webb and D. S. Houser (2000). Foraging ecology of northern elephant seals. Ecological Monographs 70(3): 353-382.
Sexual segregation in foraging is predicted from the great size disparity of male and female northern elephant seals, Mirounga angustirostris. Our aim was to test this prediction by measuring diving and foraging behavior, foraging locations, and distribution of the sexes during biannual migrations in the northeastern Pacific Ocean. Daily movements of 27 adult males and 20 adult females, during 56 migrations from Ano Nuevo, California, USA, were determined by Argos satellite telemetry via head-mounted platform transmitter terminals. Diving records were obtained with archival time-depth-speed recorders attached to the backs of seals that were recovered when the seals returned to the rookery. Pronounced sex differences were found in foraging location and foraging pattern, as reflected by horizontal transit speed and diving behavior. Males moved directly north or northwest at a mean speed of 90 plus or minus 27 km/d to focal foraging areas along the continental margin ranging from coastal Oregon (534 km away) to the western Aleutian Islands (4775 km away). Males remained in these areas (mean size = 7892 km super(2)) for 21-84% of their 4-mo stays at sea. The predominance of flat-bottom dives in these areas suggests concentrated feeding on benthic prey. Migration distance and estimated mass gain were positively correlated with male size, and individual males returned to the same area to forage on subsequent migrations. In contrast, females ranged across a wider area of the northeastern Pacific, from 38 degree to 60 degree N and from the coast to 172.5 degree E. Focal foraging areas, indicated by a reduction in swim speed to <0.4 m/s, were distributed over deep water along the migratory path, with females remaining on them a mean of 3.5 d before moving to another one. Jagged-bottom dives that tracked the deep scattering layer prevailed in these areas, suggesting that females were feeding on pelagic prey in the water column. Females took roughly similar initial paths in subsequent migrations, but large deviations from the previous route were observed. We conclude that there is habitat segregation between the sexes. Females range widely over deep water, apparently foraging on patchily distributed, vertically migrating, pelagic prey, whereas males forage along the continental margin at the distal end of their migration in a manner consistent with feeding on benthic prey.
Le Boeuf, B. J., D. E. Crocker, J. Grayson, J. Gedamke, P. M. Webb, S. B. Blackwell and D. P. Costa (2000). Respiration and heart rate at the surface between dives in northern elephant seals. Journal of Experimental Biology 203(21): 3265-3274.
All underwater activities of diving mammals are constrained by the need for surface gas exchange. Our aim was to measure respiratory rate (fB) and heart rate (fH) at the surface between dives in free-ranging northern elephant seals Mirounga angustirostris. We recorded fB and fH acoustically in six translocated juveniles, 1.8-2.4 years old, and three migrating adult males from the rookery at Ano Nuevo, California, USA. To each seal, we attached a diving instrument to record the diving pattern, a satellite tag to track movements and location, a digital audio tape recorder or acoustic datalogger with an external hydrophone to record the sounds of respiration and fH at the surface, and a VHF transmitter to facilitate recovery. During surface intervals averaging 2.2[plus/minus]0.4 min, adult males breathed a mean of 32.7[plus/minus]5.4 times at a rate of 15.3[plus/minus]1.8 breaths min-1 (means [plus/minus] S.D., N=57). Mean fH at the surface was 84[plus/minus]3 beats min-1. The fB of juveniles was 26 % faster than that of adult males, averaging 19.2[plus/minus]2.2 breaths min-1 for a mean total of 41.2[plus/minus]5.0 breaths during surface intervals lasting 2.6[plus/minus]0.31 min. Mean fH at the surface was 106[plus/minus]3 beats min-1. fB and fH did not change significantly over the course of surface intervals. Surface fB and fH were not clearly associated with levels of exertion, such as rapid horizontal transit or apparent foraging, or with measures of immediately previous or subsequent diving performance, such as diving duration, diving depth or swimming speed. Together, surface respiration rate and the duration of the preceding dive were significant predictors of surface interval duration. This implies that elephant seals minimize surface time spent loading oxygen depending on rates of oxygen uptake and previous depletion of stores.
Lehman, N., R. K. Wayne and B. S. Stewart (1993). Comparative levels of genetic variability in harbour seals and elephant seals. Symp. Zool. Soc. Lond. 66: 49-49.
Lenglart, P. Y. and M. N. Bester (1982). Post-weaning dispersion of Southern elephant seal Mirounga leonina underyearlings at Kerguelen. Terre Vie 36(2): 175-186.
Levenson, D. H. and R. J. Schusterman (1997). Pupillometry in seals and sea lions: Ecological implications. Canadian Journal of Zoology 75(12): 2050-2057.
Phocid and otariid pinnipeds forage almost exclusively under water, where observing them is difficult. As a result, little is known of how their senses are used while diving to locate and capture prey. In this study we used pupillometric methods to describe the relative visual abilities of three pinniped species: the northern elephant seal (Mirounga angustirostris), the harbor seal (Phoca vitulina), and the California sea lion (Zalophus californianus). The range of pupillary area and lower limit of pupillary adjustment were determined for each species. The northern elephant seal exhibited the largest range of pupillary area of the species examined. Furthermore, the elephant seal's pupil was found to reach maximum size only under extremely dim conditions. Both the harbor seal and California sea lion exhibited maximum pupillary dilation in conditions several log units brighter. These results indicate that the elephant seal's visual system is designed to function in dimmer conditions and to respond to greater changes in light levels than those of the harbor seal and sea lion. Such findings support the hypothesis that the visual systems of these pinnipeds are adapted for use in their respective foraging environments, and thus suggest that the visual sense is probably an important sensory modality used to locate and capture prey while diving.
Levenson, D. H. and R. J. Schusterman (1999). Dark adaptation and visual sensitivity in shallow and deep-diving pinnipeds. Marine Mammal Science 15(4): 1303-1313.
Pinnipeds forage almost exclusively underwater. Consequently, observing them is difficult and relatively little is known of how they use their senses to locate prey, avoid predators, and navigate while diving. Vision has been presumed to be of primary importance, although previous measurements of visual functioning in pinnipeds have been restricted to just a few shallow-diving species. As diving pinnipeds experience rapid changes in light levels during descent/ascent and low light levels at depth, it has not been clear whether they possess visual capabilities adequate for use while diving, particularly in the case of deep-diving species. To examine this issue, behavioral psychophysics have been used to assess and compare the dark adaptation rates and relative light sensitivities of a deep-diving pinniped (northern elephant seal, Mirounga angustirostris), two shallow-diving species (California sea lion, Zalophus californianus, and harbor seal, Phoca vitulina), and a human subject. In comparison to the human subject, both the California sea lion and the harbor seal dark-adapted relatively quickly and were more light sensitive. These findings suggest that both of these species are well suited for vision in the moderately dim shallow-water environments in which they dive to forage. In contrast, the elephant seal reached complete dark adaptation in less than half the time taken by the other pinnipeds, and it was significantly morelight sensitive. Unlike the shallower-diving species, the visual abilities of the elephant seal are commensurate with the extreme conditions experienced while deep diving. Thus, we conclude that elephant seals are sufficiently adapted to rely on vision underwater, even while diving to depths in excess of 1000 meters where bioluminescence may be the sole source of ambient light.
Lewis, M. (1989). Dinámica de la población del elefante marino del sur, Mirounga leonina, en la Península Valdés. Argentina, Universidad Nacional de La Plata.
Lewis, M. N. and C. Campagna (1995). Flipping sand in elephant seals: heat stress or just stress ? World Marine Mammal Science Conference Orlando, Florida, Lawrence, KS, Society for Marine Mammalogy.
Lewis, M. (1996). The Southern elephant seal: general biology, description of the Peninsula Valdes colony and research protocols. Pto. Madryn, Chubut (Argentina), Fundacion Patagonia Natural: 29.
There are two species of elephant seals in the world, Mirounga angustirostris and M. leonina. Both are similar in their morphological, biological and ethological features. Elephant seals are the largest of the phocids and one of the most sexually dimorphic and polygynus of the marine mammals. They dive deeper and longer than any other pinniped. They dive continuously during day and night, and spend only 2-3 min at the surface between consecutive dives. During the annual cycle, elephant seals have two terrestrial phases (breeding and molt) that alternate with pelagic phases (foraging). While on land they can be approached and the sexes easily told apart. There is detailed knowledge of the biology of the species compared to other marine mammals. This report provides a summary of current knowledge of aspects of the natural histories of the species. Research conducted on southern elephant seal on Peninsula Valdes (Argentina) is reported in two chapters that describe the biological and ecological characteristics of the species and provide research protocols for obtaining data. A detailed methodology is provided to determine age categories and sexes, estimate number of animals that breed ashore, identify animals individually and collect samples from dead individuals.
Lewis, M., C. Campagna, A. Lichter, F. Quintana and V. Falabella (1998). Demography of the growing southern elephant seal colony of Patagonia. World Marine Mammal Science Conference Monaco, Lawrence, KS, Society for Marine Mammalogy.
We report results of a long-term demographic study of the colony of southern elephant seal, Mirounga leonina, of Peninsula Valdez (PY), Argentina, the fourth largest in the world and the only one that has been expanding for three decades. The largest population of the species (South Georgia) is stable, while those of Kerguelen and Macquarie Islands, following in importance, declined by more than 50% in the last 40 years. Causes for the changes in abundance are unknown and may operate during the pelagic phases of the annual cycle. However, the demographic effects of these changes are documented during the terrestrial phases of the cycle. The accessibility of PV allows a study of the haul-out patterns for the entire area of distribution of a single population with a level of detail that is not possible for other colonies. Results of close monitoring may contribute to understanding the causes behind the decline of some populations. Aerial and terrestrial surveys of the 200 km of coastline were conducted during the peak of the breeding seas on, and terrestrial counts, covering about 80 km of coast, were conducted monthly during two years. Pup production increased 40 %, from 7,455 in 1982 to 12,379 in 1996, resulting in linear growth with an annual rate of 6 % since 1969. At the peak of the 1996 breeding season, there were 25,495 animals of both sexes ashore, including pups. The size of the population 3 1 year of age was estimated at 43,326 animals. Most (95%) females that bred at PV returned to moult there. The similar number of females during the two terrestrial phases suggests abundant and predictable food resources near PV. An age-class segregation found in the haul-out pattern, suggests a decrease of intraspecific competition at sea. The productivity of the Falkland- Malvinas Current may be a crucial determining factor of the trend of this population.
Lewis, M., C. Campagna, F. Quintana and V. Falabella (1998). Population status and distribution of southern elephant seals at Peninsula Valdes, Argentina. Mastozoologia Neotropical 5(1): 29-40.
Lewis, M., C. Campagna, F. Quintana and V. Falabella (1998). Estado actual y distribucion de la poblacion del elefante marino del sur en la Peninsula Valdes, Argentina (Population status and distribution of southern elephant seals at Peninsula Valdes, Argentina). Mastozoologia Neotropical 5(1): 29-40.
Southern elephant seals, Mirounga leonina, breed and molt in Península Valdés (PV) along a 200 km stretch of coast. We conducted one aerial survey (1992) and three terrestrial surveys (1995 to 1997) of the entire population at the peak of the breeding season (first week of October) and compared results with similar data published for the period 1982-1990. During aerial survey, we photographed all harems and recorded solitary individuals by sex and age categories (breeding females, harem bulls, bachelor males, pups and weanlings). Females were counted from photographs and pup production was estimated based on the number of females plus weanling. During terrestrial surveys, all recorded individuals were categorized by sex and age. Pup production increased 41%, from 7,455 in 1982 to 12,106 in 1997. Growth was linear from 1969 (counts made by other authors) to 1997. Based on reported pup production for the species in the world, PV is the fourth largest southern elephant seal colony. At the peak of the breeding season of 1997 there were 24,726 animals of both sexes ashore, including pups. The size of the population $1 year of age was estimated in 42,371 individuals.There were 477 harems in 1982 and 492 in 1997; 99% of the females bred in harems. The range of distribution of elephant seals in Patagonia did not change, but the spatial distribution of births along the coastline of PV varied with the increase in numbers. In 1982, 58% of the births occurred in 106 km in the NE portion of the peninsula, versus 27% in 1997. In 1997, 73% of the females gave birth in 77 km along the SE coast. Only 1% of the adult population bred outside PV. We estimated the number and distribution of adult females during the molt conducting two aerial surveys when the maximum number of animals were ashore (last weeks of December 1993 and January 1994). Females made Recibido 10 mayo 1997. Aceptado 20 abril 1998. 30 M. Lewis et al. 40% and 95% of the molting population in each census, respectively. PV is apparently the only southern elephant seal colony in the world that is expanding. The increase in pup production could be the result of factors operating while the animals are at sea, where abundant food resources may be a crucial determinant of population trends.
Lewis, M. N. and C. Campagna (1998). Flipping sand in elephant seals. Aquatic Mammals 24(3): 85-90.
Flipping sand to the dorsum with backward strokes of the foreflippers is one of the most conspicuous behaviours of elephant seals on land. Sand flipping (SF) has been described as a thermoregulatory behaviour, a response to skin irritation and a displacement activity during social conflict. We studied SF in breeding females and suckling pups of the southern elephant seal, Mirounga leonina, during the 1991 and 1994 reproductive seasons, at Peninsula Valdes (PV), Argentina. At the temperate latitude of PV (42 degree S), elephant seals are exposed to higher temperatures and solar radiation than in other colonies. Females spend 9% of the non-resting time flipping sand. Sand flipping occurred in 73% of 145 focal animal samples (FAS) taken of different females during a wide range of weather conditions. Sand flipping did not occur in 12% of 57 FAS recorded during the most stringent thermal conditions. Lactating pups displayed SF at a higher frequency than their mothers and the behaviour was also poorly correlated with the thermal context. Sand flipping occurred during rainy days, at night and during conflict situations (e.g., female harassment by males). We found no single cause for SF. It apparently serves more than one function and may better respond to internal variables than to the external environment.
Lewis, M., C. Campagna, M. Uhart and C. L. Ortiz (2001). Ontogenetic and seasonal variation in blood parameters in southern elephant seals. Marine Mammal Science 17(4): 862-872.
Blood samples were collected from 156 free-ranging southern elephant seals (Mirounga leonina) from Peninsula Valdes to study the variation in blood parameters related to ontogeny and the annual cycle. Samples ranged from newborn pups to adults. Interactions between age and sex showed different trends in ontogenetic changes of blood parameters (MANOVA, Wilkis' Lambda12,243=0.75, P<0.01). The hematocrit (HCT) and hemoglobin concentration (HB) reached adult levels early in life. Weanlings had 14% higher HCT than pups, and similar levels to juveniles and adults (HCT range=46%-62%). HB of males were below those of females from weaning (18.4 vs. 20.3 g/dl) to adulthood (19.8 vs. 22.3 g/dl). Red blood cell counts (RBC) did not change significantly from pups to juveniles (2.8-3.2 106/[mu]l), but varied for adults at different times of the annual cycle. Breeding females had higher RBC than molting females (3.1 vs. 2.4 106/[mu]l). Changes in blood parameters are related to the development of diving capabilities from pups to juveniles. Changes in adults were associated with different stages of the annual cycle, and these may be the result of the requirements imposed by pregnancy and fasting duration.
Liggins, G. C., J. T. France, R. C. Schneider, B. S. Knox and W. M. Zapol (1993). Concentrations, metabolic clearance rates, production rates and plasma binding of cortisol in Antarctic phocid seals. Acta Endocrinologica 129(4): 356-359.
We have reported previously that plasma of the Weddell seal, a member of the phocid family, contains a very high concentration of cortisol. The present study was undertaken to determine whether high cortisol levels were common to seals in the Antarctic environment, or to other phocidae, and to determine the mechanism of the hypercortisolaemia. High levels of cortisol (0.82-2.38 mumol/l) were found in 4 phocidae (Weddell, crabeater, leopard and Southern elephant seals), whereas levels in a member of the otariid family (Antarctic fur seal) were similar to human values. Metabolic clearance rates (MCR) and production rates (PR) of cortisol were determined in the field in Weddell (N = 1), crabeater (N = 3) and leopard (N = 3) seals following bolus injections of [3H] cortisol. The MCR and PR did not differ between the three phocids, but whereas the MCR of 410-590 1/day was twice that of human values, the PR of 460-1180 mumol.m-2 x d-1 was up to 40-fold greater. The binding capacity of corticosteroid-binding globulin (CBG) was equal to or greater than the plasma concentrations of cortisol, resulting in relatively low concentrations of free cortisol. We conclude that hypercortisolaemia is maintained in phocid seals mainly by a high production rate--the highest (corrected for surface area) reported in any species. The relatively low cortisol levels in otariid seals studied in the same environment suggest that the high PR in phocidae is unrelated to the harsh climatic conditions, but may be part of their adaptation for diving to extreme depths.(ABSTRACT TRUNCATED AT 250 WORDS)
Ling, J. K. and D. G. Nicholls (1963). Immobilization of elephant seals using succinylcholine chloride. Nature 200(4910): 1021-1022.
Ling, J. K., D. G. Nicholls and C. D. B. Thomas (1967). Immobilization of southern elephant seals with succinylcholine chloride. Journal of Wildlife Management 31(3): 468-479.
Succinylcholine chloride administered to 114 southern elephant seals (Mirounga leonina) by means of an extension syringe, immobilized 95 seals, with 19 failures or only partial paralysis. Seals up to 4 m in length and weighting approximately 1,900 kg were immobilized. A working dose rate of 2.5 mg/kg body weight is recommended; dose rates above 3.0 mg/kg could be fatal, but one seal survived a dose rate of 5.0 mg/kg. The syringe, methods of injection, handling procedure after immobilization, and the calculation of dose rates are described. Muscle paralysis follows a definite sequence and culminates in total collapse with or without ensuing apnoea. Recovery proceeds in the reverse order.
Ling, J. K. and M. M. Bryden (1981). Southern elephant seal - Mirounga leonina Linnaeus, 1758. Ridgway, S H; Harrison: i-xv, 1-359 Chapter pagination 297-327.
Ling, J. K. (1999). Elephant seal oil cargoes from King Island, Bass Strait, 1802-1819: with estimates of numbers killed and size of the original population. Papers and Proceedings of the Royal Society of Tasmania 133(1): 51-56.
Little, G. L., M. M. Bryden and A. Barnes (1987). Growth from birth to 20 days in the elephant seal, Mirounga leonina, at Macquarie Island. Australian Journal of Zoology 35: 307-312.
Recent investigations by members of Australian National Antarctic Research Expeditions to Macquarie I. have revealed a decrease in the elephant seal population there of approximately 50% over the last 36 years. Lower birth weights and/or slower growth during the lactation period might explain this decrease. To test this hypothesis, growth of pups was studied from birth to 20 days during the 1984 and 1985 breeding seasons; these results were compared as far as possible with similar results for the 1956 and 1965 seasons. It is concluded that, on the evidence available, the pattern of pup growth on Macquarie I. has not altered significantly with time, but more work is needed to reach a clear conclusion.
Little, G. J. and M. M. Bryden (1990). The pineal gland in newborn southern elephant seals, Mirounga leonina. J. Pineal Res. 9( 2): 139- 148.
In the newborn southern elephant seal (Mirounga leonina ) the pineal gland is very large, and both pineal and plasma melatonin concentration is elevated. The pineal gland was investigated during the first 24 h, and up to 20 days of age, in elephant seal pups. A primary aim of this investigation was to determine whether there are obvious ultrastructural characteristics of pinealocytes that are exhibiting extraordinarily high levels of activity. Blood and pineal glands were collected from thirty seven pups of known age which were sampled at random from early September to early November (1985) at Macquarie Island. The pineal gland is large and actively secreting melatonin at birth. The large and extremely active pineal gland in newborn southern elephant seal suggests that it is actively involved in thermoregulation.
Little, G. J. (1995). Body temperature in the newborn southern elephant seal, Mirounga leonina, at Macquarie Island. Marine Mammal Science 11(4): 480-490.
Newborn southern elephant seal (Mirounga leonina) pups were reported by Laws (1953) to be "to some extent poikilothermic at birth." Rectal temperatures of known age southern elephant seal pups were recorded during the 1985 pupping season at Macquarie Island. The mean pup rectal temperature was found to be 38.n degree C plus or minus 0.1 degree C SEM (n = 131, range = 36.5 degree -39.1 degree C). Pups at two hours, six hours, and one day after birth had significantly higher rectal temperatures than pups two, three, or four days of age. Rectal temperatures of neonatal southern elephant seals were within the range observed for other pinnipeds, (but never as low as the 31 degree C previously observed for southern elephant seals at Signy Island in 1953). A significant though weak positive correlation was found between pup temperature and body weight. However, no correlation between pup temperature and age or any environmental factor was found. These observations demonstrated that southern elephant seal pups at Macquarie Island are homeothermic, rather than heterothermic from birth.
Lodi, L. and S. Siciliano (1989). A southern elephant seal in Brazil.
Long, D. J., K. D. Hanni, P. Pyle, J. Roletto, R. E. Jones and R. Bandar (1996). White shark predation on four pinniped species in central California waters: geographic and temporal patterns inferred from wounded carcasses. Klimley, A Peter; Ainley: i-xi, 1-517 Chapter pagination 263-274.
Lowry, M. S., W. L. Perryman, M. S. Lynn, R. L. Westlake and F. Julian (1996). Counts of northern elephant seals, Mirounga angustirostris, from large-format aerial photographs taken at rookeries in Southern California during the breeding season. Fish. Bull. 94( 1): 176- 185.
Lydekker, R. (1909). On the skull-characters in southern sea-elephant. Proceedings of the Zoological Society of London 1909: 600-606.
M
Marquez, M. E. I., N. H. Slobodianik, P. A. Ronayne de Ferrer, A. R. Carlini, D. F. Vergani and G. A. Daneri (1995). Immunoglobulin A levels in the southern elephant seal (Mirounga leonina) milk during the suckling period. Comparative Biochemistry and Physiology B Biochemistry & Molecular Biology 112B(3): 569-572.
Immunoglobulin A (IgA) levels in milk samples from southern elephant seals at King George I. are reported. IgA levels were determined throughout the suckling period (ca 23 days). The IgA concentration in southern elephant seal milk was lower than in other mammals and, unlike most mammalian milk, was not high during early lactation. There was not a definite pattern in IgA levels, which fluctuated within narrow limits throughout the suckling period. If IgG was present, its level was too low to be detected by the method used. This is the first evidence in southern elephant seal of the possibility of transmission of passive immunity after birth involving secretion of IgA in the milk.
Marquez, M. E. I. (1998). Some biochemical data on fish and southern elephant seals from Potter Cove.
Marquez, M. E. I., A. R. Carlini, N. H. Slobodianik, P. A. Ronayne de Ferrer and M. F. Godoy (1998). Immunoglobulin M Serum levels in females and pups of southern elephant seal (Mirounga leonina) during the suckling period. Comparative Biochemistry and Physiology Part A Molecular & Integrative Physiology 119A(3): 795-799.
This paper reports Immunoglobulin M (IgM) levels in serum samples from eight female-pup pairs of southern elephant seals at King George I. IgM levels were determined on sera obtained from sequential sampling throughout the suckling period (approximately 23 days). The IgM concentration in southern elephant seal serum was measured by single radial immunodiffusion on agarose plates. Female IgM levels (123.5-613.0 mg/dL, n=8) were significantly higher than pup levels (5.9-123.6 mg/dL, n=8). Both groups showed an increasing trend throughout the entire suckling period, with significant differences in relation to stages of lactation. Pup IgM levels on the first day of life suggest that endogenous synthesis takes place before birth.
Marquez, M. E. I., A. R. Carlini, A. V. Baroni, N. H. Slobodianik, P. A. Ronayne de Ferrer and M. F. Godoy (2000). Southern elephant seals: IgM concentration in milk of cows and serum of their pups. Polar Biol. 23: 671-674.
Martensson, P. E., E. S. Norday, E. B. Messelt and A. S. Blix (1998). Gut length, food transit time and diving habit in phocid seals. Polar Biol. 20(3): 213-217.
The southern elephant seal (Mirounga leonina) has the ability to dive for 2 h and reach depths of 1200 m. This creature is also exceptional in having a small intestine that is 25 times body length. Krockenberger and Bryden advanced the hypothesis that the long small intestine has developed to compensate for the extended periods with reduced or even abolished intestinal blood perfusion during diving. To test this hypothesis we have measured small-intestinal lengths in crabeater (Lobodon carcinophagus), Weddell (Leptonychotes weddellii), Ross (Ommatophoca rossi), leopard (Hydrurga leptonyx), harp (Phoca groenlandica), ringed (Phoca hispida) and hooded (Cystophora cristata) seals and related them to available data on their maximal dive duration. We found no significant correlation (P > 0.05) between intestinal length relative to body length and diving ability, but we found that small-intestinal internal area was significantly (P < 0.05) related to body length. A crude scanning electron microscopical examination of the small intestines of Weddell, crabeater, hooded and harp seals failed to reveal any gross anatomical differences between small-intestinal surfaces. This suggests that gut dimension in this variety of phocid species with widely differing diving ability is not related to diving habit, but is instead related to body size. The transit time of digesta was determined in two 1-year-old harp seals by use of radiopaque polyethylene rings of 4-mm diameter followed by X-ray examination, as markers for the solid phase passage, and chromium ethylene-diaminetetra acetic acid (Cr-EDTA) as marker for the liquid phase. The transit time for the Cr-EDTA marker was 6.9 h +/- 0.5 SE (range 4.5-8 h, n = 7), while 80% of the polyethylene markers appeared in the colon after 17.6 h +/- 1.0 SE (range 14-21.5 h, n = 6) and were sometimes retained in the colon for several hours before defecation. These transit times did not change significantly (P > 0.05) in response to repetitive diving over a period of 8 h. This indicates that the often-used Cr-EDTA is not a good measure for digesta passage time when used alone in seals, and that the hypothesis of Krockenberger and Bryden is most likely wrong.
Marzetti, I. (1997). Comportamento riproduttivo femminile nell' elefante marino del sud (Mirounga leonina) [Female mating behaviour in southern elephant seals (Mirounga leonina)]. BAU. Roma, Italy, Università degli Studi di Roma "La Sapienza".
The target this research project was the breeding behaviour of female elephant seals (Mirounga leonina) of the Falkland Islands. In particular, we tried to explore the risks for the female due to male mating tactics, and the behavioural tactics used by females while they are on land for breeding to reduce these risks. In southern elephant seals breeding is colonial: females have a innate tendency to group when they come back to land to give birth and mate. The cause of this grouping tendency is debated: we explored the hypothesis that grouping reduce the per capita risk of harassment by males. Each group of females, called harem, is controlled by a single male, the alpha or harem master. The alpha has an almost exclusive and uncontested right of access to estrus females, and he is able to effectively keep other males away from the harem, thereby reducing the risk of harassment of females. The field work was carried on in the Falkland Islands during the 1995 and 1996 breeding seasons. The research area was Sea Lion Island, a small island that shelter a population of about five hundreds females. We tagged females and marked them with hair dye to be able to recognize them during behavioral interactions. Every day we counted the females in every harem of the population, and we identiefied as much females as possible in each harem, keeping a record of their breeding status. Estrus was estimated from birth, by adding the mean number of days from birth to first copulation calculated in a large independent sample. We observed all the harems of the population during 1258 hours in 1995 and 1294 hours in 1996. In 1996 we observed intensively a single medium sized harem for 258 hours, to collected precise information about timing of reproductive activities of individual females. During behavioural observations we recorded data about all interactions between males and females (3163 in 1995; 2849 in 1996) using all occurrences sampling; we videotaped many breeding interactions to study in detailed female reaction to male approch. We also recorded ad libitum all interaction between males and solitary females we spotted while working in the field. Male-female interactions may happens in the harem or outside the harem: the effect on the female of this two kinds of situation, and the kind of males involved, are quite different. The most of approches and copulations in and around the harem are done by alpha males. Pheripheral males will try to get in touch with harem females at any time, but their approaches are in mosta cases disrupted by alpha males. To evaluate the effect on harassment of variaous demographic and social parameters we calculated harassment indices for each harem, based on the number of interactions, the number of females and the number of associated males. We found a decrease of harassment per females with increase of harem size: in large harems harassment is distributed on a larger number of females, and hence harassment per female is lower, notwithstanding the increase in absolute harassment rate due to concentration of pheripheral males near larger harems. Hencen grouping fovours the reduction of likelyhood of harassment by males. Values of per capita indices of harassment by pheripheral males are very low: hence, while in the harem each female has to interact mainly with a single and experieced male, the likelyhood of heavy harassment is low, and the likelyhood of disruption by other males is almost nil. Hence, the main risks for females during their permanence in harems are interruption of lactation and separation from the pup that may result form interaction with the alpha male. In northern elephant seals (M. angustirostris) the likelyhood of pup separation is high, and in many cases separation results in definitive abandonment of the pup. Thus, male mating behavior is a significant source of pup mortality in this species. In our population of souther elephant seals the situation was quite different: in many cases reproductive interactions resulted in disruption of lactation and separation of of the pup from the mother, but in no case this separation was definitive and lead to abandonment. These mild effect of male mating behaviour depends on the density of Sea Lion Island population, which is very low if compared with the high density typical of the northern species and the bigger colonies of the southern. On Sea Lion Island harems are small and not very crowded: hence the pup has a great likelyhood to be able to come back to his mother aftera temporary separation. Outside the harem the main risk for breeding females is harassment from secondary males. The libido of these males is very high, as is demonstrated by the capability to copulate at fast pace when, due to random events, an harem remains without alpha. Chances to be able to get actual mates is, on the contrary, very low: they are strongly limited in their access to females by the action of alphas. Hence, these males concentrated on consorting with females ouside the harems (rare isolated females, pregnant females in arrival from sea, post estrus females in departure to sea). They usually heavily harass females, and this harassmente may potentially have a cost for the females (disruption of energy and time budget, wounds, breeding in unfit areas). In the northern species, harassment from pheripheral male may result in serious wounding, and is a serious source of female mortality. On the contrary, in our study population, serious wounding of females is very rare, and in no case it resulted in death of the female involved or definitive abandonment of the breeding ares. In spite of this, also in our population, female breeding behavior revealed may different fine tuning to reduce the risk of interception by secondary males.
Matthews, L. H. (1929). The natural history of the elephant seal, with notes on other seals found at South Georgia. Disc. Rep. 1: 233-256.
Mawson, P. R. and D. K. Coughran (1999). Two recent records of southern elephant seal (Mirounga leonina) births in Western Australia. Western Australian Naturalist 22(3): 195-197.
McCann, T. S., W. N. Bonner, J. Prime and C. Ricketts (1979). Age distribution and age at first pregnancy of South Georgia elephant seals, Marine Mammals Committee.
The age-distribution and age at first pregnancy of a sample of Elephant seal taken at South Georgia was determined by examination of sections of canine teeth. No significant difference was noted in the age at first pregnancy over the period covered by the sample.
McCann, T. S. (1980 a). Population structure and social organization of Southern elephant seals, Mirounga leonina (L.). Biological Journal of the Linnean Society 14: 133-150.
M. leonina was studied at South Georgia principally by extensive field census work and determination of age and reproductive history from sections of teeth taken from samples of bulls and cows. The adult males of the South Georgia population were exploited from 1910 to 1964, mainly at the maximum sustainable yield for this population. The present data are compared with similar information obtained from studies at South Georgia in 1951 during the exploitation phase and at Macquarie Island in the 1950's where sealing ended in 1919 and the population had stabilized. Changes have been noted in the time of bull haul out, number of bulls ashore, cow:bull ratio, harem size and the age of harem bulls. These changes can all be attributed to the ending of exploitation. In contrast, the structure of the cow herd has not changed appreciably in the same period. In addition, differences in growth, body size and population structure still persist between the South Georgia and Macquarie Islpopulations and which reflect differences in food availability at the 2 locations.
McCann, T. S. (1981). Aggression and sexual activity of male Southern elephant seals, Mirounga leonina. Journal of Zoology London 195: 295-310.
The agonistic and sexual activity of individual male Southern elephant seals (Mirounga leonina) was studied during the breeding season at South Georgia. Harem bulls were older and larger than non-harem bulls and, althouyh size and age are related, harem bulls were also larger than non-harem bulls of the same age. Large body size conferred advantages in fiyhting and the agonistic relationships of the bulls gave rise to a dominance hierarchy with access to harems and activity within harems, beiny determined by rank. Vocalizations were the most highly rank-related aggressive behaviours. The most common vocalization, the roar, probably functioned in both individual recognition and size assessment. Over 90 % of encounters of high-ranked bulls were ''walkovers'' and only 4 % of 4003 agonistic interactions involved physical contact. The time of greatest sexual activity differed between hiyh-ranked and low-ranked bulls. Low-ranked bulls were most active at the time of maximum harem size when they had greatest access to the harem but, because few cows were in oestrus at this time, they achieved few copulations. Experienced bulls appeared to use a particular behaviour, termed '~heading" to detect cows in oestrus. Copulation frequency was related to rank: of 331 observed copulations, the first-ranked bull achieved 38 % and the top five bulls 88 %. High-ranked bulls were most active, sexually and aggressively, when the number of females in oestrus was greatest, suggesting that the most dominant bulls adjusted their activity in relation to the costs and benefits involved.
McCann, T. S. (1982). Aggressive and maternal activities of female southern elephant seals (Mirounga leonina). Animal Behaviour 30: 268-276.
McCann, T. S. (1983). Activity budgets of southern elephant seals, Mirounga leonina, during the breeding season. Zeitschrift fuer Tierpsychologie 61: 111-126.
McCann, T. S. (1985). Size, status and demography of Southern elephant seal (Mirounga leonina) populations. Studies of sea mammals in South Latitudes. J. K. L. M. M. Bryden. Northfield, South Austr. Museum: 1-17.
The current status of southern elephant seals populations is reassessed using original census data form all major breeding sites. Methods for evaluationg annual pup production from counts at breeding beaches are reviewed in detail and a relationship derived, based on counts of cows alone, which is shown to be more accurate than those previously used.
Life tables, based on data from Macquarie Island and South Georgia, are constructed and used to estimate relationships between pup production and total population size. The total population of alla animals older than pups of the year is calculated to be 3.5 times annual pup production. The total population of southern elephant seals is estimated as approximately 750000, which is 10-25% grater than hitherto suggested. In the light of this, new estimates of population biomass and food consumption are derived. These suggest that the stocks of fish in the waters around South Georgia and Kerguelen have been understimated.
McCann, T. S. and P. Rothery (1988). Population size and status of the southern elephant seal (Mirounga leonina) at South Georgia, 1951-1985. Polar Biology 8(4): 305-309.
McCann, T. S., M. A. Fedak and J. Harwood (1989). Parental investment in southern elephant seals, Mirounga leonina. Behavioral Ecology and Sociobiology 25: 81-87.
The southern elephant seal is among the most sexually dimorphic and polygynous of all mammals: males may be more than 10 times the weight of reproducing females and only the largest 2-3% of males are likely to breed. Current optimization theories of sexual selection predict that evolution would favor greater parental investment in individual males than in females. Because southern elephant seals represent an extreme of polygyny and sexual dimorphism, they might be expected to show a dramatic difference in parental investment in male and female pups. However, in a study of parental investment in elephant seals at South Georgia, using several different methods, we found no such difference after parturition. Mother-pup pairs were immobilized and weighed early in lactation, recaptured near the end of lactation and reweighed. A further 30 pups were weighed an average of five times during lactation to establish the shape of the growth curve and to serve as partial controls for the previous set of animals. Initial post-partum weight in females ranged from 346 to 803 kg (x= 506, SD=111, n=26). Pup birth weight was related to mothers' post-partum weight in female pups but small females often gave birth to large male pups. Male pups were significantly heavier at birth than females. However, this size difference did not persist. Male and female pups were suckled for the same period, grew at the same rate and were not significantly different in weight at weaning. Mothers lost weight at the same rate regardless of their pup sex.
McConnell, B. J., C. Chambers and M. A. Fedak (1992). Foraging ecology of southern elephant seals in relation to the bathymetry and productivity of the Southern Ocean. Antarct. Sci. 4(4): 393-398.
Southern elephant seals (Mirounga leonina) are among the most proficient of mammalian divers and are a major component of the Antarctic food web. Yet little is known of their movements or interaction with their oceanic environment. Specially designed satellite-link data loggers allowed us to visualize the 3-D movements of elephant seals as they swam rapidly from South Georgia to distant (up to 2650 km) areas of Antarctic continental shelf. One seal dived continuously to the sea bed in one small area for a month, implying consumption of benthic prey. Dives here were shorter even though average swimming velocity was lower. It is suggested that the physiological requirements of feeding and digestion reduced the aerobic dive limit. Long distance travel to relocatable hydrographic or topographical features, such as shelf breaks, may allow large predators to locate prey more consistently than from mid-ocean searches.
McConnell, B. J. and M. A. Fedak (1996). Movements of southern elephant seals. Canadian Journal of Zoology 74(8): 1485-1496.
Twelve southern elephant seals (Mirounga leonina) were tracked for an average of 119 days as they left their breeding or moulting beaches on the island of South Georgia between 1990 and 1994. Females travelled either eastward up to 3000 km away to the open Southern Ocean or to the continental shelf on or near the Antarctic Peninsula. Males either stayed close to South Georgia or used South Georgia as a base for shorter trips. The females all left South Georgia in a directed manner at an average rate of 79.4 km/day over at least the first 15 days. Thereafter travel was interrupted by bouts of slower travel or stationary phases. The latter were localized at sites on the continental shelf or along its edge. Three seals that were tracked over more than one season repeated their outward direction of travel and used some of the same sites in subsequent years. The magnitude of the movements makes most of the Southern Ocean potentially available to elephant seals.
McDermid, E. M., R. Ananthakrishnan and N. S. Agar (1972). Electrophoretic investigation of plasma and red cell proteins and enzymes of Macquarie Island elephant seals. Anim. Blood Groups Biochem. Genet. 3: 85-94.
Electrophoretic investigations of the protein and enzyme groups of 8 plasma and of 11 red cell systems have been carried out on 42 samples of seals of the species Mirounga leonina (L.) from Macquarie Island. Variation was demonstrated in the following 5 systems: phosphoglucomutase, red cell acid phosphatase, phosphohexose isomerase, albumin and pre-albumin.
McGinnis, S. M. and R. J. Schusterman (1981). Northern elephant seal Mirounga angustirostris Gill, 1866. Ridgway, S H; Harrison: i-xv, 1-359 Chapter pagination 329-349.
McLean, I. G. and R. B. Russ (1994). Birds and mammals of Solander (Hautere) Island. Notornis 41(3): 213-215.
McMahon, C. R., j. van den Hoff, H. R. Burton and P. D. Davis (1997). Evidence for precocious development in female pups of the southern elephant seal Mirounga leonina at Macquarie Island. Marine mammal research in the southern emisphere. Vol.1. Status, ecology and medicine. M. H. C. K. (Eds.). Chipping Norton, Surrey Beatty: 92-96.
McMahon, C. R., H. R. Burton and M. N. Bester (1999). First-year survival of southern elephant seals, Mirounga leonina, at sub-Antarctic Macquarie Island. Polar Biology 21(5): 279-284.
Juvenile seals branded on the isthmus of Macquarie Island as pups displayed a high degree of philopatry. They returned more often and in greater densities to the northern third of the island within 10 km of their birth sites. Juvenile seals were observed to haul out more frequently and in greater numbers on the east coast as opposed to the west. Juvenile seals typically hauled out on two occasions, once during the winter, and once to moult. The probability of recapturing (resighting) branded and tagged seals was greater during the mid-year haulout. First-year survival estimates were obtained from searches of all Macquarie Island beaches for marked (branded and tagged) seals. From a branded population of 2000 seals, 897 were known to be alive at age 1 year, and minimum first-year survival was calculated at 44.85%. To this minimum estimate was added the number of seals overlooked during systematic and standardised searches of the island, and a revised estimate of 65.60% was calculated. Survival rates calculated using a custom model and a conventional mark-recapture model (MARK) were compared and no differences detected. Actual survival data and probability of sighting estimates were included in the revised estimate of first-year survival of southern elephant seals at Macquarie Island. There were no differences in the number of surviving males and females.
McMahon, C. R., H. Burton, S. McLean, D. Slip and M. Bester (2000). Field immobilisation of southern elephant seals with intravenous tiletamine and zolazepam. Vet Rec 146(9): 251-4.
Southern elephant seals (Miroungo leonina) were immobilised with a mixture of tiletamine and zolazepam administered intravenously at a mean (sd) dose rate of 0.46 (0.08) mg/kg. This dose provided a satisfactory degree of anaesthesia with no side effects, and the induction, duration and recovery times were short. The mean (sd) induction time was 26 (9) seconds and the mean level of anaesthesia was 4.4 units on an eight-point scale. Male seals were given less drug than female seals, remained immobilised for shorter periods and recovered sooner. The mean (sd) dose of drug administered to males was 0.44 (0.06) mg/kg and to females 0.48 (0.08) mg/kg, and the mean (sd) duration times were 14.9 (4.5) minutes and 16.1 (5.3) minutes. The mean (sd) time taken to recover from immobilisation was 14.5 (4.6) minutes for males and 15.7 (5.3) minutes for females. Physiological condition and size significantly affected the duration of anaesthesia. Thin seals remained immobilised for 18 (7) minutes whereas fatter seals remained immobilised for 15 (4) minutes (P<0.0001).
McMahon, C. R., H. R. Burton and M. N. Bester (2000). Weaning mass and the future survival of juvenile southern elephant seals, Mirounga leonina, at Macquarie Island. Antarctic Science 12(2): 149-153.
Seals that survived their first year were on average 2% and 4% heavier at birth and at weaning than the "non-survivors". First year survival rates calculated for weaners over 135 kg weaning masses showed these weaners had higher survival rates than those less than 95 kg at weaning (71.55% and 54.15% respectively). Heavy weaners had greater fat reserves than light weaners and gained relatively more mass during lactation. Size, and therefore condition at weaning, influences first year survival.
McMahon, C. R. and D. Campbell (2000). Southern elephant seals breeding at Peterson Island, Antarctica. Polar Record 36(196): 51.
A single elephant seal pup was sighted at Peterson Island during the 1997/98 austral summer. The pup was observed being suckled by its mother and then alone during the post-weaning fast. The pup was weaned after 24 days and spent 44 days ashore after weaning. These statistics are consistent with those recorded at Macquarie Island (McMahon and others 1997), from where the breeding seals are believed to have originated. Tagging studies conducted at Macquarie Island and at Peterson Island show some migration between the two sites (ANARE unpublished data).
McMahon, C. R., I. Field, T. Dorr, C. Hammond and D. Washington (2000). Hook and nose: an interaction between a male southern elephant seal and a long-line fishery. Polar Record 36(198): 250-252.
McMahon, C. R. and C. J. Bradshaw (2004). Harem choice and breeding experience of female southern elephant seals influence offspring survival. Behavioral Ecology and Sociobiology 55(4): 349-362.
Female mammals can increase their lifetime fitness through modification of investment potential and by providing better rearing environments with improved breeding experience. We examined the relationships between reproductive fitness and the behavioural decisions that female southern elephant seals (Mirounga leonina) made during the breeding season. We examined whether mother age and breeding experience influenced reproductive success (measured as 1st-year survival probability), and whether there was a change in the choice of harem size with increasing age. Pups produced by young mothers had lower 1st-year survival probability than pups produced by older mothers. A significant increase in mean female mass with age required an analysis of both these effects on offspring survival. There was a significant positive effect of both female age and mass, and the interaction between the two, on 1st-year pup survival. The proportion of young mothers (<5 years old) decreased and the proportion of older mothers (>6 years old) increased with increasing harem size (harems surveyed from 1997 to 2001). Females chose larger harems in which to breed as they aged. Females demonstrated fidelity to breeding areas among successive breeding seasons, with older females displaying greater breeding-site fidelity than younger females. The mean number of previous breeding attempts per female within a harem (breeding experience) increased significantly with increasing harem size. Breeding females returned to breed later in the breeding season as they aged-we hypothesize that young, subordinate females gain a priority advantage by returning earlier. These results lend support to the hypothesis that there are fitness advantages, in terms of offspring survival, that are conferred to females that breed in successively larger harems with age. Potential mechanisms that select for females to improve their breeding conditions include improved mate selection and the avoidance of conspecific harassment in harems.
McMahon , C. R., H. R. Burton and M. N. Bester (2003). A demographic comparison of two southern elephant seal populations. Journal of Animal Ecology 72: 61_74.
1. To estimate concurrent age-specific survival for southern elephant seals at Macquarie and Marion islands, seals were marked from 1993 to 1997 in the first 3 weeks of life and resighted (recaptured) on return to their natal islands (1994–2001). These recaptures formed the basis for the survival analysis in the mark–recapture program MARK . Weaning masses were collected at each location. 2. Recapture probabilities were ( = 376·480, P < 0·0001) higher at Marion Island than at Macquarie Island. There are two possible reasons: (1) the population at Marion Island is smaller and less dense than at Macquarie Island and (2) seals hauled out along a smaller section of the coast at Marion Island than at Macquarie Island, which: (1) facilitates the detection and individual identification of seals and (2) increases access to hauled out seals. 3. Age-specific survival estimates (corrected for preweaning mortality and tag loss) differed ( = 22·264, P < 0·05) at the two islands and were consistently higher at Macquarie Island. The survival estimates for male and female seals were different at Macquarie Island ( = 34·657, P < 0·0001) and Marion Island ( = 20·373, P = 0·002). Female survival estimates were higher than male survival estimates. The combined survival estimates for juvenile seals (1–3 years) differed between islands but survival of older seals (4–6 years) did not. The inclusion of gender in the survival models did not improve model performance and hence male and female estimates were considered jointly. 4. The mean wean masses of male and female seals combined from 1993 to 1998 were not different between islands (T 6837 = 1·169, P = 0·242). At Macquarie Island the mean annual wean mass was 118·8 kg (SD = 27·2, n = 6504) while at Marion Island it was 120·6 kg (SD = 24·7, n = 335). 5. The mean age at first breeding was different ( P < 0·001) at the two island populations. At Macquarie Island the mean age of first breeding was 4·68 years, and at Marion Island it was 3·95 years. More ( = 67·39, P < 0·0001) 3-year-old females breed at Marion Island (28·7%) than at Macquarie Island (1·2%) and the proportion of seals that had bred at least once by age 7 was greater at Marion Island than at Macquarie Island. 6. We conclude that the observed decreases in elephant seal numbers between the 1950s and 1990s in the Pacific and Indian Ocean sectors were driven principally by resource limitation in the Southern Ocean. A conglomerate of factors including local predation by killer whales and intraspecific resource competition is postulated as a cause for the inter-island (regional) differences in population trends. It appears that more resources are available per capita to the Marion Island population than are available to the Macquarie Island population.
Key-words : environmental change, mark–recapture, sub-Antarctic, survival, wean mass.
Meiselman, H. J., M. A. Castellini and R. Elsner (1992). Hemorheological behavior of seal blood. Clinical hemorheology 12: 657-675.
Seals place extreme demands on circulatory blood flow during dives, yet hemorheological information for these marine mammals is limited. This report contains the results of an investigation of several hematologic and rheologic parameters in three phocid seals: elephant seals (ES), ringed seals (RS) and Weddell seals (WS). Salient results included: 1) elevated hematocrit; 2) large MCV; 3) increased MCHC, with calculated RBC cytoplasmic viscosities based on MCHC being two- to four-fold higher than human; and 4) species-specific fibrinogen levels. RBC aggregation was also species specific: 1) extent of aggregation; 2) aggregate strength; and 3) ZSR. Blood viscosity data again indicated variations among species; WS blood was markedly non-Newtonian with elevated low shear viscosity, whereas RS blood exhibited much lower, nearly Newtonian viscosity. ES blood was intermediate in flow behavior. Viewed collectively, these results indicate marked rheologic "abnormalities" for seal blood which, however, are not associated with pathophysiologic findings; they thus suggest adaptive mechanisms in these animals and the potential value of aquatic mammals as model systems for clinical hemorheology studies.
Melrose, W. D., M. M. Feast, R. Woods, A. McMinn, D. M. L. Jupe and P. A. Bell (1995). Haematology, red cell enzymes, and red cell metabolic intermediates of 20 wild southern elephant seals (Mirounga leonina) from Macquarie Island. Comparative Haematology International 5(1): 1-6.
Mesnick, S. L. and B. J. Le Boeuf (1991). Sexual behavior of male northern elephant seals: II. Female response to potentially injurious encounters. Behaviour 117(3-4): 262-280.
During mating attempts by males, female elaphant seals, Mirounga angustirostris, are sometimes injured or killed as they return to sea at the end of lactation. We tested two predictions from the general hypothesis that females behave in a way that reduces the possibility of injury or death from sexual encounters with males: 1) departing females attempt to avoid males, and 2) if males cannot be avoided, departing females exhibit sexually receptive behavior to males, and thereby reduce the threat of injury from aggressive mating attempts.
Circumnstances surrounding the departure of 336 females from harems on the Ano Nuevo harem in central California were recorded over the course of nine breeding seasons form 1982-1990. Females do little to avoid encounters with males surrounding harems; they don't leave in grater number at night, in groups, or during disturbances on the harem periphery. They did, however, leave harems preferentially at high tide which reduced the distance to the water and shortened transit time. Most departing females did lot resist the mating attempts of peripheral males but, rather, they were unusually receptive. Receptive females received fewer blows capable of producing injury than resisting females. We conclude that receptive behavior in this context "buys safe passage". It is an effective means of reducing male aggression and the probability of injury; a male has no need to restrain a receptive female with blows, and should the most dominant male in the area copulate with a departing female, he frequentli escort her to sea and defenids her from other males.
Mesnick, S. L., M. d. C. Garcia Rivas, B. J. Le Boeuf and S. M. Peterson (1998). Northern elephant seals in the Gulf of California, Mexico. Marine Mammal Science 14(1): 171-178.
Since its near extinction by nineteenth-century sealers, the population of northern elephant seals (Mirounga angustirostris) has increased exponentially, recovering its historical range and colonizing new breeding sites. Currently, northern elephant seals breed on thirteen islands and four mainland sites from Isla Cedros in Baja California Sur, Mexico, to Cape Arago, Oregon, USA. Le Boeuf et al. (1996) reported observations of stray juveniles as far away as Amaknak Island in the Aleutian Islands, Midway Island and Hokkaido, Japan. There are no historical records to indicate whether elephant seals occurred in the Gulf of California, prior to 1979, when the first known observation was made. Here, we summarize recent records of northern elephant seals in the Gulf of California with respect to age, gender, and distribution.
Milsom, W., M. Castellini, M. Harris, J. Castellini, D. Jones, R. Berger, S. Bahrma, L. Rea and D. Costa (1996). Effects of hypoxia and hypercapnia on patterns of sleep-associated apnea in elephant seal pups. American Journal of Physiology 271(4 Part 2): R1017-R1024.
This project examined the effects of alterations in respiratory drive on the occurrence of sleep apnea in Northern elephant seal pups (Mirounga angustirostris). Sleep pattern was unaffected by levels of hypoxia (similar to 13%) or hypercapnia (similar to 6%) that doubled respiratory frequency during slow-wave sleep (SWS). During sleep in air, short periods of continuous breathing (mean length = similar to 2.6 min) alternated with periods of apnea (mean length = similar to 6.1 min). Under hypoxic or hypercapnic conditions, the frequency of occurrence of apneas was reduced primarily due to the occurrence of some sleep episodes without periods of apnea. In episodes in which apneas did occur, they began later in the sleep episodes, but their length and the length of the periods of eupnea were not significantly altered. During each period of eupnea, however, the instantaneous respiratory rate and the total number of breaths increased. Breathing during sleep was restricted to SWS, never occurring during rapid eye movement (REM) sleep, regardless of the respired gas mixture. If the levels of hypoxia and hypercapnia were raised further, all episodes of apnea during sleep could be eliminated together with all episodes of REM sleep. One interpretation of the data is that the threshold for altering breathing during eupnea (instantaneous breathing frequency and number of breaths per episode of eupnea) is lower than that for altering the lengths of the periods of apnea and eupnea and that the muscle atonia associated with REM. sleep extends to all respiratory muscles. [References: 23]
Mitchell, P. J. and H. R. Burton (1991). Immobilisation of southern elephant seals and leopard seals with cyclohexamine anaesthetics and xylazine. Vet. Rec. 129(15): 332-336.
Ketamine and xylazine were given to 55 southern elephant seals (Mirounga leonina) for stomach lavaging, and to three leopard seals (Hydrurga leptonyx). The elephant seals showed prolonged apnoea and two of them died owing to aspiration of stomach contents. Two of the leopard seals died from unknown causes. Tiletamine and zolazepam were given to five elephant seals and one leopard seal. Two of the elephant seals and the leopard seal died from unknown causes. Xylazine alone was administered to 34 leopard seals. Sedation was poor at low dose rates (less than 1.7 mg/kg) but four of the seals given higher dose rates died owing to the aspiration of stomach contents.
Modig, A. O. (1996). Effects of body size and harem size on male reproductive behaviour in the southern elephant seal. Animal Behaviour 51(6): 1295-1306.
In a study on size and reproductive behaviour in the southern elephant seal, Mirounga leonina, on South Georgia from 1991 to 1993, large size, measured as nose to hind flipper length, was associated with factors that confer an advantage in terms of reproductive success. Some males stayed at the centre of harems, others were on the periphery and others were outside the harem. A male's mating success increased with his length, and for central males, mating success increased with harem size. Central males defeated almost all other males. Central males were also longest and outside males shortest. Furthermore, central males stayed ashore longest. For central males, length was positively correlated with number of days spent in the harem but not with harem size. Central and peripheral males had the highest copulation frequencies (per h and per male). The copulation frequency of central males apparently peaked in harems with a maximum size of 100-150 females, with lower frequencies in larger and smaller harems. However, the mating success of central males over the season increased with harem size. The rate of alert behaviour and time devoted to resting were not correlated with harem size for any of the three male categories, but rate of agonistic behaviour increased with increasing harem size for central males.
Modig, A., H. Engstrom and T. Arnbom (1997). Postweaning behaviour in pups of the southern elephant seal (Mirounga leonina) on South Georgia. Canadian Journal of Zoology 75(4): 582-588.
After weaning, southern elephant seal pups (Mirounga leonina) fast for 3-8 weeks, for largely unknown reasons. During the postweaning fast we observed daytime behaviour and movements of pups on South Georgia in relation to mass, sex, and tooth eruption. There was variation in behaviour, with the lowest levels of activity from about 09:00 to 15:00. When ashore, weaned pups spent 97% of the time resting. There was no difference in activity between the sexes, except that only male pups were observed fighting. There was a significant difference in tooth eruption between the sexes. In female pups, 87.9% had teeth at weaning, while only 28.7% of male pups had. There was no correlation between mass at weaning and activity in either sex. Weaned pups tended to gather in groups (median group size 3, range 2-67). Several factors may affect the behaviour of pups during the postweaning fast: the resting behaviour required to save energy favours spending time ashore during the day (which also enhances vitamin D synthesis), and foraging is more effectively practiced at night because their prey is more active at night.
Moore, P. G. (1994). Observations on the behaviour of the scavenging lysianassoid Orchomene zschaui (Crustacea: Amphipoda) from South Georgia (South Atlantic). Marine Ecology Progress Series 113(1-2): 29-38.
Orchomene zschaui (Pfeffer, 1888) dominated the catch of scavengers attracted to heads of dead elephant seals suspended above the sea bed at Husvik, South Georgia. No ovigerous female, and few juvenile, amphipods were captured. Activity was nocturnal. No lunar rhythm in catch rate was detected: encounters with bait (by visiting shoals of amphipods?) seemed to be by chance. Habitat choice experiments revealed a kinetic preference for dark vs light places, antipathy towards sand and a consistent choice of alternatives which offered high surface contact. Amphipods survived 4 ppt salinity for 30 min. Temperatures between -2 and +10 degree C were tolerated, but rapid removal from +2 degree C to +12 degree C resulted in heat shock effects. In the field, amphipods nestled into the pelt of the seal head, often near a facial orifice, and began penetration of the epidermis, creating larger and larger holes with time. The stomach of O. zschaui occupies 41% of body length. Analysis of stomach contents showed that consumption of dark epidermal tissue (as strips) only preceded white blubber, i.e. never followed it. The degree of stomach fullness of amphipods captured at night increased progressively through the hours of darkness. The rate at which stomach fullness declined with time depended on the material consumed: 9 to 10 d for seal epidermis, 2 d for blubber. Replete amphipods lose some 20% of total dry weight if starved for 23 d.
Morejohn, G. V. and K. T. Briggs (1973). Post mortem studies of Northern elephant seal pups. Journal of Zoology London 171: 67-77.
Moritz, C., S. Lavery and R. Slade (1995). Using allele frequency and phylogeny to define units for conservation and management.
Morris, P. A. (1995). Rate of mass loss of juvenile northern elephant seals during haulouts. World Marine Mammal Science Conference Orlando, Florida, Lawrence, KS, Society for Marine Mammalogy.
Mortenson, J. and M. Follis (1997). Northern elephant seal (Mirounga angustirostris) aggression on harbor seal (Phoca vitulina) pups. Marine Mammal Science 13(3): 526-530.
Muller-Schwarze, D., E. C. Waltz, W. Trivelpiece and N. J. Volkman (1978). Breeding status of southern elephant seals at King George Island. Antarct. J. U.S. 13(4): 157-158.
A census of elephant seals at Stranger Point, King George I., revealed a main colony and four satellite colonies. The main colony had 4 groups, each with 1 harem bull and from 28 to 52 females. The females had 76 pups. Each satellite colony had a harem bull; one had one peripheral bull, and another had three. Numbers of females ranged from 9 to 42, pups from 4 to 20. The entire eastern snow-slope contained 12 bulls, 222 cows, and 114 pups. Additional elephant seals were seen in the distance. Apparently Oct. 12 was near the peak during pupping time. The overall cow to bull ratio at Stranger Point was higher than the Macquarie I. or South Georgia ratios. A small breeding colony exists at Point Thomas in Admiralty Bay.
Murphy, R. C. (1914). Notes on the sea elephant, Mirounga leonina (Linneo). Bull. Am. Mus. Nat. Hist. 33: 63-79.
Murphy, C. G. (1998). Interaction-independent sexual selection and the mechanisms of sexual selection. Evolution 52(1): 8-18.
Darwin identified explicitly two types of sexual selection, male contests (combat and displays) and female choice, and he devoted the overwhelming majority of his examples to traits that influence the outcome of these interactions. Subsequent treatments of sexual selection have emphasized the importance of intra- and intersexual interactions as sources of sexual selection. However, many traits that are important determinants of mating success influence mating success without necessarily affecting the outcome of intra- and intersexual interactions. Here, I argue that traits can be subject to sexual selection even if they do not affect the outcome of intra- and intersexual interactions. I distinguish two types of sexual selection, interaction-independent and interaction-dependent selection, based on whether variance in mating success is the result of trait-dependent outcomes of interactions between conspecifics. I then use this distinction to construct a framework for classifying types of sexual selection that unifies and expands previously proposed frameworks. Finally, I outline several implications that the concept of interaction-independent sexual selection has for the general theory of sexual selection.
Murray, M. D. and D. G. Nicholls (1965). Studies on the ectoparasites aof seals and penguins. I. The ecology of the louse Lepidophthirus macrorhini Enderlein on the southern elephant seal, Mirounga leonina (L.). Australian Journal of Zoology 13: 437-454.
Murray, M. D. (1981). The breeding of the southern elephant seal, Mirounga leonina L., on the Antarctic continent. Polar Record 20(127): 370-371.
Sightings of southern elephant seals and pups over the period 1972-1979 suggest that a breeding colony for this species is being established on the antarctic continent in Vincennes Bay on Peterson Island (66.5S 110.5E).
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Naito, Y., B. J. le Boeuf, T. Asaga and A. C. Huntley (1989). Long-term diving records of an adult female northern elephant seal. Antarctic Record 33(1): 1-9.
Nakajima, M., K. Maejima, K. Kohyama, A. Furuta and Y. Fujimaki (1999). A morphological study on the southern elephant seal, Mirounga leonina. Journal of Japanese Association of Zoological Gardens and Aquariums 41(1): 3-10.
Nakajima, M. and S. Nomura (1999). A case of miscarriage in a southern elephant seal, Mirounga leonina. Journal of Japanese Association of Zoological Gardens and Aquariums 41(1): 18-20.
Nelson, G. J. (1970). Lipid composition of the blood of marine mammals. 1. Young elephant seals, Mirounga augustirostris and harp seals, Pagophilus groenlandicus. Comparative biochmistry and physiology 34(1): 109-116.
Nepomnaschy, P. A. (1994). Estructura de los harenes del elefante marino del sur (Mirounga leonina). Su relacion con aspectos del comportamiento social individual. Puerto Madryn (Chubut - Argentina), Universitad Nacional De La Patagonia San Juan Bosco.
Newman, J. W., J. Vedder, W. M. Jarman and R. R. Chang (1994). A method for the determination of environmental contaminants in living marine mammals using microscale samples of blubber and blood. Chemosphere 28(10): 1795-1805.
A method for the determination of environmental contamination of juvenile northern elephant seals (Mirounga angustirostris) was developed. Blubber and blood samples were collected. Blubber samples were ground with sodium sulphate and extracted with hexane:methylene chloride (1:1). Serum samples were extracted on C18 columns. The serum and blood extracts were separated on a micro-Florisil column and analysed by high resolution gas chromatography with electron capture detection. Lipid determination in serum samples was conducted by colorimetry.
Nicholls, D. G. (1970). Dispersal and dispersion in relation to birthsite of the Southern elephant seal, Mirounga leonina (L.) of Macquarie Island. Mammalia 34(4): 598-616.
Nordoy, E. S. and A. S. Blix (1997). Studies of seals in the Weddell Sea and King Haakon VII Sea.
Noren, S. R., T. M. Williams, D. A. Pabst, W. A. McLellan and J. L. Dearolf (2001). The development of diving in marine endotherms: Preparing the skeletal muscles of dolphins, penguins, and seals for activity during submergence. Journal of Comparative Physiology B Biochemical Systemic and Environmental Physiology 171(2): 127-134.
Myoglobin is an important oxygen store for supporting aerobic diving in endotherms, yet little is known about its role during postnatal development. Therefore, we compared the postnatal development of myoglobin in marine endotherms that develop at sea (cetaceans) to those that develop on land (penguins and pinnipeds). We measured myoglobin concentrations in the major locomotor muscles of mature and immature bottlenose dolphins (Tursiops truncatus) and king penguins (Aptenodytes patagonicus) and compared the data to previously reported values for northern elephant seals (Mirounga angustirostris). Neonatal dolphins, penguins, and seals lack the myoglobin concentrations required for prolonged dive durations, having 10%, 9%, and 31% of adult values, respectively. Myoglobin contents increased significantly during subsequent development. The increases in myoglobin content with age may correspond to increases in activity levels, thermal demands, and time spent in apnea during swimming and diving. Across these phylogenetically diverse taxa (cetaceans, penguins, and pinnipeds), the final stage of postnatal development of myoglobin occurs during the initiation of independent foraging, regardless of whether development takes place at sea or on land.
Noren, D. P. (2002). Thermoregulation of Weaned Northern Elephant Seal (Mirounga angustirostris) Pups in Air and Water. Physiol Biochem Zool 75(5): 513-23.
Fasting weaned northern elephant seal pups (Mirounga angustirostris) experience diverse environmental conditions on land and in water on a daily basis. Each environment undoubtedly induces distinct energetic costs that may vary for pups of differing body condition. To determine the energetic costs associated with different environmental conditions and whether costs vary between individuals, body mass, surface area, volume, body composition, resting metabolic rate, and core body temperature were determined for 17 weaned northern elephant seal pups from Ano Nuevo, California. Metabolic rate and body temperature were measured for pups resting in air (20.9j0;+/-0.8j0;C), cold water (3.8j0;+/-0.4j0;C), and warm water (14.5j0;+/-0.2j0;C). Resting metabolic rate increased with body mass (range: 62.0-108.0 kg) and was also correlated with lean mass and lipid mass. Metabolic rates ranged from 293.6 to 512.7 mL O(2) min(-1) and were lowest for pups resting in cold water. Thermal conductance, calculated from metabolic rate and core body temperature, ranged from 3.1 to 15.2 W degrees C(-1), with the highest values in air and the lowest values in cold water. Metabolic responses to the three environmental conditions did not differ with individual variation in body condition. For all elephant seal pups, a consequence of high lipid content is that thermoregulatory costs are greatest on land and lowest in cold water, a pattern that contrasts markedly with terrestrial mammals.
Noren, D. P. (2002). Body energy reserves utilization during the postweaning fast of northern elephant seals (Mirounga angustirostris): implications for survival. Department of Biology. Santa Cruz, California, University of California.
Noren, D. P., D. E. Crocker, T. M. Williams and D. P. Costa (2003). Energy reserve utilization in northern elephant seal ( Mirounga angustirostris) pups during the postweaning fast: size does matter. Journal of Comparitive Physiology B 21: 21.
During fasting most mammals preferentially utilize lipid reserves for energy while sparing protein reserves. This presents a potential problem for marine mammals that also depend on lipids as a major component of blubber, the primary thermoregulatory structure. Because of this dual function for lipid, rates of lipid and protein utilization should be closely regulated during the postweaning fast in northern elephant seals ( Mirounga angustirostris). To quantify energy expenditure during the fast, we measured body mass and composition of 60 pups at 2.3+/-0.2 days and 55.9+/-0.3 days postweaning in 1999 and in 2000. Body condition differed significantly between years. At weaning, body mass (125.9+/-3.8 kg) and percentage lipid content (39.3+/-0.6% of body mass) in 2000 were significantly greater than body mass (115.2+/-3.1 kg) and percentage lipid content (35.8+/-0.6%) in 1999. In general, percentage lipid content increased with body mass, and fatter pups utilized lipid at relatively higher rates during the fast. Lipid fueled 85-95% and 88-98% of energy expended by pups in 1999 and 2000, respectively. Postweaning fast duration (32-78 days) was positively correlated with body mass and hence lipid content at weaning. This suggests that body composition at weaning influences lipid utilization patterns and ultimately the duration of the postweaning fast in northern elephant seal pups.
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Odell, D. K. (1972). Studies on the biology of the California sea lion and the northern elephant seal on San Nicholas Island, California. Los Angeles, California, University of California.
Odell, D. K. (1977). Structure of northern elephant seal population breeding on San Nicholas Island, California, in 1971. Animal Behaviour 25(1): 208-214.
The structure of the population of northern elephant seals, Mirounga angustirostris, on San Nicolas Island, California, was studied during the 1970 and 1971 breeding season. At the population peak on 31 January 1971, there were 77 males, 306 females, 315 pups, and 6 yearlings on shore. The breeding population was subdivided into 15 groups, containing from 3 to 75 breeding animals. Fourteen of the groups were considered territories defended by individual males, and one group, the largest, was controlled by three males in a social hierarchy. The relatively small size of the San Nicolas population and the large amount of available beach space allowed the existence of numerous small breeding groups. Female elephant seals, although gregarious, apparently prefer to be in small groups when conditions permit it. It is likely that the same males that were territorial would have formed the nucleus of a social hierarchy if space had been limited enough to cause all of the females in the population to congregate in one large group. PMID- 0000857710
Keywords: Breeding, California, Hierarchy, Pinnipedia, Population, Pregnancy, Seals, Social Dominance
Oliver, G. W., P. A. Morris, P. H. Thorson and B. J. L. Boeuf (1998). Homing behavior of juvenile northern elephant seals. Marine Mammal Science 14(2): 245-256.
The aim of this study was to determine if juvenile northern elephant seals, Mirounga angustirostris, translocated from their rookery would return to it quickly and reliably. During the spring and fall of 1990 and 1991 we captured 75 seals at Año Nuevo State Reserve, CA, U.S.A, and translocated them to release sites up to 100 km away. Eighty-eight percent of the seals returned to the capture site within 4.7 ± 4.3 d. Homing rate increased with age, but even the youngest seals (8–10 mo) homed at a 73% rate. Homing rate did not vary significantly with sex, season, or year. Data from diving instruments suggested that the seals often followed direct routes home, arrived on the rookery significantly more often at night than during the day, and when released together, returned separately. Mean homing speed of 18 seals with complete diving records was 39 km/d (range 3–70 km/d). Instruments on seals had no detectable effect on homing rate or homing speed. The translocation paradigm provides a powerful tool for conducting intensive short-term studies on free-ranging seals.
Oosthuizen, W. H., J. H. M. David and G. J. B. Ross (1988). New records of southern elephant seals Mirounga leonina L. on the coast of southern Africa. S. Afr. J. Mar. Sci. 7( 75-86).
Systematic recording of elephant-seal (Mirounga leonina ) sightings, including 92 hitherto unpublished records, has increased the number of records on the coast of southern Africa to 130. The number of sightings has increased recently. The overall sex ratio is 52.4% male to 21% female, being of indeterminate sex. The seals haul out mainly from November to February. The most likely primary cause of haul-out for immature seals is to moult. It is postulated that the seals originated mainly from South Georgia. It is not clear if the seals recorded are true vagrants or the outer fringe of a normal dispersal.
Ortiz, C. L., D. Costa and B. J. le Boeuf (1978). Water and energy flux in elephant seal pups fasting under natural conditions. Physiological Zoology 51(2): 166-178.
Ortiz, C. L., B. J. Le Boeuf and D. P. Costa (1984). Milk intake of elephant seal pups: an index of parental investment. American Naturalist 124(3): 416-422.
Total milk ingested throughout nursing in free-living northern elephant seal pups, derived from the turnover of tritiated water, gives an accurate estimate of the energetic component of parental investment. In 4 wk of nursing, females transferred a mean of 138 kg of milk with a value of 6.04 x 105 kcal, five times the metabolic requirements of pups. The mean rate of energy transfer is more than twice that predicted for the female's size from studies of laboratory and domestic animals. In one month, pups receive sufficient energy and essential nutrients from mother's milk to enable them to fast while continuing to develop for an additional 2 1/2 mo before feeding on their own. Measurement of the energetic component of parental investment makes it possible to test predictions from the theory of parental investment.
Ortiz, R. M., C. E. Wade and C. L. Ortiz (2000). Prolonged fasting increases the response of the renin-angiotensin-aldosterone system, but not vasopressin levels, in postweaned northern elephant seal pups. General and Comparative Endocrinology 119(2): 217-223.
The 8- to 12-week postweaning fast exhibited by northern elephant seal pups (Mirounga angustirostris) occurs without any apparent deleterious effects on fluid and electrolyte homeostasis. However, during the fast the role of vasopressin (AVP) has been shown to be inconclusive and the involvement of the renin-angiotensin-aldosterone system (RAAS) has yet to be examined. To examine the effects of prolonged fasting on these osmoregulatory hormones, 15 postweaned pups were serially blood-sampled during the first 49 days of their fast. Fasting did not induce significant changes in ionic or osmotic concentrations, suggesting electrolyte homeostasis. Total proteins were reduced by day 21 of fasting and remained depressed, suggesting a lack of dehydration. Aldosterone and plasma renin activity exhibited a correlated, linear increase over the first 49 days of the fast, suggesting an active RAAS. Aldosterone exhibited a parabolic trend over the fast with a peak at day 35, suggesting a shift in the sensitivity of the kidney to aldosterone later in the fast. AVP was elevated at day 49 only, but concentrations were relatively low. RAAS was modified during the postweaning fast in pups and appears to play a significant role in the regulation of electrolyte and, most likely, water homeostasis during this period.
Ortiz, R. M., C. E. Wade and C. L. Ortiz (2001). Effects of prolonged fasting on plasma cortisol and TH in postweaned northern elephant seal pups. American Journal of Physiology 280(3 Part 2): R790-R795.
Northern elephant seal (Mirounga angustirostris) pups rely on the oxidation of fat stores as their primary source of energy during their 8- to 12-wk postweaning fast; however, potential endocrine mechanisms involved with this increased fat metabolism have yet to be examined. Therefore, 15 pups were serially blood sampled in the field during the first 7 wk of their postweaning fast to examine the changes in plasma concentrations of cortisol and thyroid hormones (TH), which are involved in fat metabolism in other mammals. Cortisol increased, indicating that it contributed to an increase in lipolysis. Increased total triiodothyronine (tT3) and thyroxine (tT4) may not reflect increased thyroid gland activity, but rather alterations in hormone metabolism. tT3-to-tT4 ratio decreased, suggesting a decrease in thyroxine (T4) deiodination, whereas the negative correlation between total proteins and free T4 suggests that the increase in free hormone is attributed to a decrease in binding globulins. Changes in TH are most similar to those observed during hibernation than starvation in mammals, suggesting that the metabolic adaptations to natural fasting are more similar to hibernation despite the fact these animals remain active throughout the fasting period.
Ortiz, R. M. (2001). Endocrinology of fasting and renal function in pups of the Northern elephant seal (Mirounga angustirostris). Department of Biology. Santa Cruz, California, University of California.
Ortiz, R. M., C. E. Wade, D. P. Costa and C. L. Ortiz (2002). Renal responses to plasma volume expansion and hyperosmolality in fasting seal pups. Am J Physiol Regul Integr Comp Physiol 282(3): R805-17.
Renal responses were quantified in northern elephant seal (Mirounga angustirostris) pups during their postweaning fast to examine their excretory capabilities. Pups were infused with either isotonic (0.9%; n = 8; Iso) or hypertonic (16.7%; n = 7; Hyper) saline via an indwelling catheter such that each pup received 3 mmol NaCl/kg. Diuresis after the infusions was similar in magnitude between the two treatments. Osmotic clearance increased by 37% in Iso and 252% in Hyper. Free water clearance was reduced 3.4-fold in Hyper but was not significantly altered in Iso. Glomerular filtration rate increased 71% in the 24-h period after Hyper, but no net change occurred during the same time after Iso. Natriuresis increased 3.6-fold in Iso and 5.3-fold in Hyper. Iso decreased plasma arginine vasopressin (AVP) and cortisol acutely, whereas Hyper increased plasma and excreted AVP and cortisol. Iso was accompanied by the retention of water and electrolytes, whereas the Hyper load was excreted within 24 h. Natriuresis is attributed to increased filtration and is independent of an increase in atrial natriuretic peptide and decreases in ANG II and aldosterone. Fasting pups appear to have well-developed kidneys capable of both extreme conservation and excretion of Na(+).
Ortiz, R. M., D. S. Houser, C. E. Wade and C. Leo Ortiz (2003). Hormonal changes associated with the transition between nursing and natural fasting in northern elephant seals (Mirounga angustirostris). Gen Comp Endocrinol 130(1): 78-83.
To better interpret previously described hormonal changes observed during the natural postweaning fast (2-3 months) endured by pups of the northern elephant seal (Mirounga angustirostris), we compared plasma cortisol, thyroid hormones, and leptin in pups (n=5) measured during nursing and fasting periods. Blood samples were taken at four times; early (9 days postpartum) and late (18-22 days postpartum) nursing, and early (second week postweaning) and late (eighth week postweaning) fasting. Plasma cortisol increased 39% between early and late nursing and almost 4-fold by late fasting. After the early nursing period, cortisol and body mass were negatively correlated (y=28.3-0.19x; R=0.569; p=0.027). Total thyroxine (tT(4)), free T(4) (fT(4)), total triiodothyronine (tT3) and reverse T(3) (rT(3)) were greatest at early nursing and reduced by late nursing and remained so throughout the fast, with the exception of tT(4), which increased between late nursing (17.7+/-2.1ngmL(-1)) and late fasting (30.1+/-2.8ngmL(-1)) periods. Leptin remained unaltered among the four sampling periods and was not correlated with body mass. Pups appear to exhibit a shift in the relationship between cortisol and body mass suggesting a potential role for cortisol in the regulation of body fat. The higher concentrations of tT(3) and tT(4) during early nursing may reflect enhanced growth and development during this period, however the increase late in fasting is likely physiologically insignificant and an artifact of reduced metabolic clearance of these hormones. Transition of the pups from nursing to fasting states is characterized by a striking lack of change in cortisol, thyroid hormones, and leptin suggesting that any metabolic alterations associated with this transition may occur independent of these hormones.
Ortiz, R. M., D. P. Noren, C. L. Ortiz and F. Talamantes (2003). GH and ghrelin increase with fasting in a naturally adapted species, the northern elephant seal (Mirounga angustirostris). J Endocrinol 178(3): 533-9.
After nursing, pups of the northern elephant seal (Mirounga angustirostris) are approximately 46% body fat and rely almost entirely on the oxidation of their large fat stores to sustain their metabolism for the ensuing 8-12 week postweaning fast, which is a natural component of their life history. Thus, fasting pups provide an ideal opportunity to examine the hormonal alterations associated with prolonged food deprivation in a naturally adapted model. Cortisol, ghrelin, glucagon, growth hormone (GH), insulin-like growth factor-I (IGF-I), insulin, blood urea nitrogen (BUN), glucose and non-esterified fatty acids (NEFA) were examined in 20 male and 20 female pups blood sampled early (<1 week postweaning) and late (6-8 weeks postweaning) during the fast. Mean cortisol, ghrelin, GH, and glucagon increased 1.8-, 1.8-, 1.4-, and 2.3-fold between early and late periods, while mean IGF-I and insulin decreased 97% and 38%, respectively. NEFA increased 2.3-fold, while BUN and glucose decreased 46% and 11%, respectively. NEFA was significantly and positively correlated with cortisol and GH; individually; however, when the relationship was examined as a multiple regression the correlation improved suggesting that cortisol and GH act synergistically to promote lipolysis during the fast. GH and BUN were negatively and significantly correlated between early and late fasting suggesting that GH may promote protein sparing as well. The decrease in glucose may be responsible for stimulating glucagon, resulting in the maintenance of relative hyperglycemia. The increases in cortisol, ghrelin, glucagon, and GH suggest that these hormones may be integral in mediating the metabolism of seal pups during prolonged fasting.
Ortiz, R. M., C. E. Wade and C. L. Ortiz (2003). Body water handling in response to hypertonic-saline induced diuresis in fasting northern elephant seal pups (Mirounga angustirostris). Comp Biochem Physiol A Mol Integr Physiol 134(2): 423-8.
During natural fasting conditions in postweaned northern elephant seal (NES) (Mirounga angustirostris) pups, urinary water loss is minimized and percent total body water (TBW) is maintained constant. However, following infusion of hypertonic saline, glomerular filtration rate (GFR) and urine output increased in fasting pups. Therefore, we quantified the magnitude of the hypernatremia-induced diuresis relative to the animal's total body water (TBW) pool and the percentage of filtered water reabsorbed. Following a 24 h control period, naturally fasting NES pups (n=7) were infused (4 ml min(-1)) with hypertonic saline (16.7%) at a dose of 3 mmol NaCl kg(-1) body mass. Total body water was estimated prior to infusion by tritium dilution, GFR was estimated by standard creatinine clearance, and urine output (V) was measured for 24 h during the control and post infusion periods. Percentage of filtered water reabsorbed was calculated as (1-(V/GFR))x100. Twenty-four hours following the infusion, GFR (control: 69+/-12 ml min(-1) and post-infusion: 118+/-19 ml min(-1); mean+/-S.E.) increased 77+/-28% above control and the percentage of filtered water reabsorbed was decreased 0.4+/-0.1%. The increase in urine output (control: 218+/-47 ml d(-1) and post-infusion: 883+/-92 ml d(-1)) accounted for 1.7+/-0.2% of the pups' TBW. The hypernatremia-induced diuresis was accompanied by the loss of body water indicating the lack of water retention. Although the 77% increase in GFR was only associated with a 0.4% decrease in the percentage of filtered water reabsorbed, this decrease was significant enough to result in a 4-fold increase in urine output. Despite the observed diuresis, fasting NES pups appear to possess an efficient water recycling mechanism requiring only a small percentage of body water to excrete an excess salt load. This water recycling mechanism may allow pups to avoid negative perturbations in body water as they initiate feeding in a marine environment following the fast.
Ortiz, R. M., C. E. Wade, C. L. Ortiz and F. Talamantes (2003). Acutely elevated vasopressin increases circulating concentrations of cortisol and aldosterone in fasting northern elephant seal (Mirounga angustirostris) pups. J Exp Biol 206(Pt 16): 2795-802.
The physiological actions of vasopressin (VP) in marine mammals are not well defined. To help elucidate its hormonal and renal effects in this group of mammals, northern elephant seal (Mirounga angustirostris) pups (N=7; 99+/-4 kg) were first infused with 0.9% saline (control; 220 ml), followed 24 h later with VP (as a 20 ng kg(-1) bolus, then 2 ng kg(-1) min(-1) for approximately 35 min in 225+/-16 ml saline). During both control and VP periods, blood samples were collected prior to infusion, and 15, 30, 60, 120 min and 24 h after infusion to examine the hormonal responses of the pups to VP. Renal responses were quantified from 24 h urine samples obtained prior to infusion (control) and 24 h post-infusion. Compared to the control period, infusion of VP increased plasma concentrations of cortisol over a 120 min period and aldosterone over 30 min, while plasma renin activity (PRA) was decreased for a 120 min period. The plasma urea:creatinine ratio was elevated following infusion of VP. Urine output and osmotic clearance were increased by 69+/-18% (mean +/- S.E.M.) and 36+/-10%, respectively, but free water clearance and glomerular filtration rate were not significantly altered 24 h post-infusion of VP. Solute (osmolality, Na(+), K(+) and Cl(-)) excretion and fractional excretion of electrolytes were also increased when compared to control values. The increase in cortisol concentration suggests that VP may possess corticotropin releasing hormone-like activity in elephant seals. If osmotic diuresis and natriuresis are typical consequences of elevated [VP] in fasting pups, then not increasing VP normally during the fast may serve as a protective mechanism to avoid the potential loss of Na(+) induced by elevated [VP]. Therefore, under natural fasting conditions, pups may be highly sensitive to small changes in [VP], resulting in the maintenance of water and electrolyte balance.
Oziurdzik, B. (1989). Histological structure of hair of the southern elephant seal, Mirounga leonina (Linnaeus, 1758) (Pinnipedia, Mammalia).
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Panagis, K. (1981). Local movement of southern elephant seal pups Mirounga leonina (Linn.) at Marion Island.
Panagis, K. (1984). Influence of southern elephant seals, Mirounga leonina, on the coastal moulting areas at Marion Island. S. Afr. J. Sci. 80(1): 30.
Two plant community complexes and six associations, resulting from activity at the moulting sites of southern elephant seals, are described. Chemical analyses of the soil show an increase in concentrations of all the mineral nutrients in the molt areas. The biomass figures for the mesofauna of the two study sites are 5.3 g/sq m and 3.90 g/sq m, respectively, significantly lower than those given by other authors.
Pascal, M. (1979). Essai de dénombrement de la population d' éléphants de mer (Mirounga leonina (L.)) des îles Kerguelen (49 °S, 69 °E). Mammalia 43(2): 147-159.
Pascal, M. (1985). Numerical changes in the population of elephant seals (Mirounga leonina L) in the Kerguelen Archipelago during the past 30 years. Marine mammals and fisheries. J. H. B. D. M. L. E. R. Beddington. London, George Allen & Unwin: 170-186.
Census results from surveys conducted in 1970 (Pascal 1979) and 1977 (Van Aarde 1980) indicated a clear decline in the population of elephant seals frequenting the Kerguelen Archipelago. Between 1958 and 1961, approximately 6000 males were removed from the population by the Societé Industrielle des Abbettoirs Parisiens. Since that time the population has not been exploited. In this paper, techniques are developed to quantify the abundance of the population from census data. The causes of the marked decline in the size of the population are considered.
Patterson-Buckendahl, P., S. H. Adams, R. Morales, W. S. S. Jee, C. E. Cann and C. L. Ortiz (1994). Skeletal development in newborn and weanling northern elephant seals. American Journal of Physiology 267(3 2): R726-R734.
Pemberton, D. and I. J. Skira (1989). Elephant seals in Tasmania. Victorian Naturalist(Blackburn): 202-204.
Pernia, S. D., D. P. Costa and C. L. Ortiz (1989). Glomerular filtration rate in weaned elephant seal pups during natural, long term fasts. Canadian Journal of Zoology J. Can. Zool. 67( 7): 1752- 1756.
Low urine output (<200 mL/day) seen in weaned elephant seal (Mirounga angustirostris) pups is consistent with the physiological necessity of strict water conservation during periods of protracted, natural fasts. However, urine output represents only the difference between glomerular filtration rate (GFR) and tubular reabsorption and thus provides no information about the absolute magnitude of these parameters or their role in homeostatic regulation during the fast. We measured GFR, and extracellular volume (ECV) and estimated tubular reabsorption in seven pups that had been fasting >6 weeks and in three others that had begun to feed in captivity using standard [ super(3)H]inulin and [ super(125)I]iothalamate clearance techniques. In fasting pups, GFR and ECV ranged from 78.9 to 135.2 mL/min and from 6.3 to 15.4 L, respectively. The GFR values are 59-91% (x super(-) = 69 plus or minus 10%) of that predicted by standard body mass allometry. These data suggest that (i) low urine output is a consequence of tubular reabsorption rather than depressed GFR; (ii) a small but significant N and electrolyte load resulting from oxidation and reorganization of body tissue during development requires near "normal" renal function despite the potential loss of water from excess urine formation.
Perry, E. A., S. M. Carr, S. E. Bartlett and W. S. Dividson (1995). A phylogenetic perspective on the evolution of reproductive behavior in pagophilic seals of the Northwest Atlantic as indicated by mitochondrial DNA sequences. Journal of Mammalogy 76(1): 22-31.
The ice-breeding (pagophilic) habits and relatively short lactation periods of several species of "true" seals (Phocidae) of the Northwest Atlantic, including the harp seal (Pagophilus) bearded seal (Erignathus), and hooded seal (Cystophora), usually are assumed to have evolved in parallel. Current taxonomy regards Pagophilus and ringed seals (Pusa) along with harbor seals (Phoca vitulina) as subgenera of Phoca, unites Phoca (sensu lato) together with gray seals (Halichoerus) and Erignathus in the subfamily Phocinae, and places Cystophora with elephant seals (Mirounga) in a separate subfamily. Cystophorinae. Cladistic analysis of variation in the DNA sequence of the mitochondrial cytochrome b gene identifies three clades among northern seals: Phoca-Pusa-Halichoerus, Cystophora-Pagophilus, and Erignathus. Erignathus is the sister group to the other species examined. Each clade may be regarded as a tribe of the subfamily Phocinae (the Phocini, Cystophorini, and Erignathini, respectively). The phylogeny suggests that the ice-breeding habit and associated brief lactation are ancestral characters for the Phocinae and that instances of fast-ice or terrestrial breeding are convergences on the ancestral condition in other phocid subfamilies.
Petrinovich, L. F. (1974). Individual recognition of pup vocalization by Northern elephant seal mothers. Zeitschrift Fuer Tierpsychologie 34: 308-312.
Piatkowski, U., D. F. Vergani and Z. B. Staganelli (2002). Changes in the cephalopod diet of southern elephant seal females at King George Island, during El Nino-La Nina events. Journal of the Marine Biology Association UK 82(3972): 1-5.
Pistorius, P. A., M. N. Bester and S. P. Kirkman (1999). Dynamic age-distributions in a declining population of southern elephant seals. Antarctic Science 11(4): 445-450.
Estimates of births and standing age-distributions were combined to estimate the size of the southern elephant seal population at Marion Island at various times during its decline. To estimate births each year from 1986 through 1997 we used the number of adult females hauled out on 15 October, which is the peak haulout date for breeding elephant seal females at all breeding sites in the Indian Ocean. A conversion factor (3.15) was derived from the standing age-distributions, and applied to estimates of annual births to yield total population size. The population at Marion island declined 37.5% overall from 1986-97 at an annual rate of 4.3% from 1986-91 and c. 2.5% uyr super(-1) afterwards.
Pistorius, P. A., M. N. Bester and S. P. Kirkman (1999). Survivorship of a declining population of southern elephant seals, Mirounga leonina, in relation to age, sex and cohort. Oecologia 121(2): 201-211.
This study quantified both the age- and sex-specific survival rates of juveniles and adults, and tested for interannual differences in age-specific survival rates of the southern elephant seal population at Marion Island. Pups were tagged on an annual basis from 1983 onwards at Marion Island, and a consistent recapture program yielded data that was analysed using the software package MARK to obtain maximum-likelihood estimates of survival and capture probability. On average, 1st-year survival was 0.58 and 0.62, and survival rate averaged over the first 3 years of life, 0.69 and 0.74 for males and females, respectively. From years 4 to 9, the average survival rate was 0.66 and 0.75 for males and females, respectively. Survival estimates for elephant seals in their 10th-13th year are also presented, although these are based on very small sample sizes. Averages of age-specific survival estimates from the earlier (mostly 1983-1987 cohorts) and later (mostly 1988-1992 cohorts) periods were compared and considerable reductions were observed in 4th- and 5th-year male survival, and 4th-year female survival. The comparatively low adult survival is suggested as the proximate cause, and food limitation as deduced from the decline in survival of elephant seals with comparatively high energetic demands as the ultimate cause behind the population decline at Marion Island. Although not tied in with the decline of the population, 1987, 1990 and 1993 were identified as high-mortality years.
Key words Survival , Decline , Mark-recapture , Elephant seals , Marion Island
Pistorius, P. A., M. N. Bester, S. P. Kirkman and P. L. Boveng (2000). Evaluation of age- and sex-dependent rates of tag loss in southern elephant seals. Journal of Wildlife Management 64(2): 373-380.
Rates of tag loss were estimated in a long-term tagging study of southern elephant seals (Mirounga leonina) to assess the potential for bias in estimates of survival rates. Dalton Jumbo Rototags(R) were applied to each hind flipper of 5,743 recently weaned elephant seal pups on Marion Island from 1983 to 1993. We adapted and developed a method based on the resighting times of seals retaining 1 or 2 tags to estimate tag loss and test for effects of age and sex of the seals. Tag loss by young seals was low, but there was a strong increase in tag loss with seal age, especially for males. Annual single tag loss at age 14 was 10% for males and 5.6% for females. Although these are relatively modest rates of tag loss, substantial fractions of sea ls (35% of males and 17% of females) would lose both tags by age 15, requiring corrections to avoid bias in demographic studies based on these tagging data. The method we used to estimate tag loss has significant advantages over a ratio estimator that ha s been used for most previous studies of tag loss in pinnipeds.
Pistorius, P. A., M. N. Bester, S. P. Kirkman and F. E. Taylor (2001). Temporal changes in fecundity and age at sexual maturity of southern elephant seals at Marion Island. Polar Biology 24(5): 343-348.
Our objective was to examine the effect of variation in reproductive parameters on the demography of southern elephant seals at Marion Island. We used age-specific capture probabilities of breeding females in a Cormack-Jolly-Seber context to derive reproductive rates. We found that age at maturity declined and fecundity rates increased as the population declined, indicating a compensatory response. Fecundity rates ranged from 0.03 to 0.29 among 3-year-olds (mean = 0.16), 0.18 to 0.50 in 4-year-olds (mean = 0.40), and 0.28 to 0.50 in 5-year-olds (mean = 0.45). We think that a relative increase in food availability, concomitant with the population decline, promoted earlier sexual maturity correlated with more rapid growth of juveniles when population abundance was lower. It is suggested that the relative importance of fecundity in population regulation in elephant seals has been underestimated. Moreover, it appears that the onset of sexual maturity may be the first demographic variable to change in response to a change in population density.
Pistorius, P. A., M. N. Bester, S. P. Kirkman and F. E. Taylor (2001). Pup mortality in souther elephant seals at Marion Island. Polar Biology 24: 828-831.
Pistorius, P. A. and M. N. Bester (2002). A longitudinal study of senescence in a pinniped. Canadian Journal of Zoology 80: 395-401.
To measure the prevalence of senescence in southern elephant seals (Mirounga leonina Linn.) at Marion Island, changes in adult-female survival and breeding probabilities with age were quantified. Mark–recapture data that had been collected over a 17-year period were analysed using recently developed software to obtain likelihood estimates of survival and capture probabilities. With recapture effort constant over the study period, capture probabilities during the breeding seasons were used as indices of breeding probabilities. Longevity in the population was assessed from the resighting of tagged and hence known-age individuals. Less than a 1% difference between prime-age survival and post prime age survival was found over 8 cohorts of marked females. In addition, no reduction in survival of very old individuals was detected, suggesting the absence of senescence in terms of reduced survival in southern elephant seals. No evidence of reproductive senescence in terms of reduced breeding probability with age was detected. Mortality throughout the population therefore resulted in no individuals surviving to the age where physiological decline would become a mortality agent or result in failure to breed. Five percent of female southern elephant seals survived to age 10 and 0.5% to age 17.
Pistorius, P. A. and M. N. Bester (2002). Juvenile survival and population regulation in southern elephant seals at Marion Island. African Zoology 37(1): 35-41.
We examined annual juvenile survival in southern elephant seals (Mirounga leonina) at Marion Island for the period 1994-1999 during which time the population was stable. Using mark-recapture models, we tested for age- and sex-specific differences in survival rates over the first three years of life. We found that survival was age- but not sex-related and compared our estimates to similar estimates from a previous study on the same population while in a state of decline. This was done to determine whether changes in juvenile survival were instrumental in terminating the population decline at Marion Island. On average, the probability of survival was 59.5%, 81.4% and 78.1% for the first, second and third year respectively. These estimates were remarkably similar to those previously calculated for the population while in a state of decline, and we dismiss juvenile survival as a major population regulating component in southern elephant seals at Marion Island.
Ponganis, P. J., U. Kreutzer, N. Sailasuta, T. Knower, R. Hurd and T. Jue (2002). Detection of myoglobin desaturation in Mirounga angustirostris during apnea. American Journal of Physiology 282(1 Part 2): R267-R272.
H NMR solution-state study of elephant seal (Mirounga angustirostris) myoglobin (Mb) and hemoglobin (Hb) establishes the temperature-dependent chemical shifts of the proximal histidyl N[delta]H signal, which reflects the respective intracellular and vascular Po2 in vivo. Both proteins exist predominantly in one major isoform and do not exhibit any conformational heterogeneity. The Mb and Hb signals are detectable in M. angustirostris tissue in vivo. During eupnea M. angustirostris muscle maintains a well-saturated MbO2. However, during apnea, the deoxymyoglobin proximal histidyl N[delta]H signal becomes visible, reflecting a declining tissue Po2. The study establishes a firm methodological basis for using NMR to investigate the metabolic responses during sleep apnea of the elephant seal and to secure insights into oxygen regulation in diving mammals.
Pugh, P. J. A. (1996). The structure and function of the tarsus I sensillar field in mites of the genus Halarachne (Halarachnidae: Gamasida). Journal of Natural History 30(7): 1069-1086.
The sensillar field on tarsus I of Halarachne (Halarachnidae: Gamasida), a respiratory tract endoparasite of seals (Pinnipedia) is associated with 12 hair- or peg-like receptor sensilla in the larva and 13 or 14 in the adult. These include thermo- /hygroreceptors, each with a double wall traversed by 3 or 4 slit-like pores (dw/WP-sensilla), olfactory chemoreceptors of small inorganic molecules, each with a single wall spanned by several small and simple pores (sw/WP-sensilla), gustatory chemoreceptors with a single terminal pore (TP-sensilla), and aporous NP-sensilla which have thermoreceptive and/or other unknown functions. Some sensilla are sessile and others socketed, the latter having a possible additional/alternative mechanoreceptive function. One mechanoreceptor is a probable trichobothrium-like vibration receptor which has not been previously described in the Anactinotrichida. This range of sensilla combined with the absence of sw/WP-sensilla, i.e. olfactory chemoreceptors covered with numerous, large centrally-plugged pores, suggests that although Halarachne spp. can locate large endothermic animals, they lack the ability to discriminate between different species.
Puppione, D. L., C. M. Kuehlthau, R. J. Jandacek and D. P. Costa (1996). Chylomicron triacylglycerol fatty acids in suckling northern elephant seals (Mirounga angustirostris) resemble the composition and the distribution of fatty acids in milk fat. Comparative Biochemistry and Physiology B Biochemistry & Molecular Biology 114B(1): 53-57.
Pyle, P., S. D. Anderson and D. G. Ainley (1996). Trends in white shark predation at the South Farallon Islands, 1968-1993. Klimley, A Peter; Ainley: i-xi, 1-517 Chapter pagination 375-379.
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Quintana, F., C. Campagna, D. Crocker and B. J. Le Boeuf (1995). Diving behaviour of female southern elephant seals in Patagonia. World Marine Mammal Science Conference Orlando, Florida, Lawrence, KS, Society for Marine Mammalogy.
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Radford, K. W., R. T. Orr and C. L. Hubbs (1965). Reestablishment of the northern elephant seal (Mirounga angustirostris) off central California. Proc. Calif. Acad. Sci. 31: 601-612.
Rakusa-Suszczewski, S. and K. Sierakowski (1993). Pinnipeds in Admiralty Bay, King George Island, South Shetlands (1988-1992). Polish Polar Research 14(4): 441-453.
Ramdohr, S., J. Plotz, H. Bornemann, C. Engelschalk, J. Thiery and R. Eisen (1998). Studies on the lipoproteins of the southern elephant seal (Mirounga leonina) during the breeding season at King George Island. Berichte zur Polarforschung 299: 243-248.
Ramdohr, S., H. Bornemann, J. Plötz and M. N. Bester (2001). Immobilization of southern elephant seal bulls (Mirounga leonina) in polar regions. Verhandlungsbericht des 40. Internationalen Symposiums über die Erkrankungen der Zoo- und Wildtiere, Rotterdam/Niederlande, Alfred Wegener Institut for Polar and Marine Research.
Studies on wild pinnipeds such as blood and tissue sampling or attachment of instruments usually require immobilization. This is particularly true for adult male southern elephant seals whose body mass generally exceeds 2 tons, and hence, a suitable chemical restraint is required for any handling. Therefore, both appropriate drugs and a remote delivery system as generally applied in wild animal research is required (CLINE et al., 1969; TRILLMICH and WIESNER, 1979; KOCK, 1987; BUSH, 1992). Wild elephant seals are only accessable during their onshore-periods while breeding and moulting. At this time, they fast and hence undergo considerable metabolic changes. The individuals' constitutions are then highly variable, and the reaction to external stimuli ranges from being calm to being aroused. Thereby, the dosage of drugs is hardly to assess, and the response to drugs is variable (HAMMOND and ELSNER, 1977). Estimation of body mass is also difficult since moulting males tend to aggregate tightly in large groups when ashore, occasionally lying over and over. The harsh field conditions in polar regions aggravate the work additionally. Therefore, both a sturdy drug delivery system, and some considerations on the methods of application are recommended. In the present study, 27 animals were immobilized to obtain subcutaneous tissue samples, and to attach satellite linked dive recorders to their pelage at the end of their annual moult. Prior to immobilization, doses were calculated roughly based on the estimated body mass. Immo-bilization was performed in two steps. Firstly, Large Animal Immobilon® (LA Immobilon®) was injected remotely to achieve initial sedation (x=0.0009 mg/kg etorphine; 0.0037 mg/kg acepromacine). As the second step, if breathing and reflexes occured regularly, ketamine was subsequently injected by hand to maintain narcosis (x=81 min). Nine cases required the application of the etorphine-antidote Large Animal Revivon® (x=0.0052 mg/kg diprenor-phine) injected intraveneously (n=3), intramuscularly (n=5), or sublingually (n=1) to antagonize side effects such as prolonged apnea and/or decrease of reflexes. Results and Discussion The total dosages of ketamine required to maintain narcosis (x=1.7 mg/kg) were negatively correlated with those of LA Immobilon® (p<0.01). The dosages of LA Immobilon® were approximatelly 15-30 times lower than recommended for other large-sized mammal species including marine mammals (ALFORT et al., 1974; BORN and KNUTSEN, 1990; GRIFFITH et al., 1993), and the therapeutic range was low. LA Immobilon® appears nevertheless to be useful as a first-step immobilization agent in adult male southern elephant seals owing to its small volume required for remote injection, and the possibility of high specific antagonization by Large Animal Revivon®. We nevertheless suggest that LA Immobilon® should only be used as a kind of pre-medication, not used repeatedly in the same individual, and solely if high specific antidote (Large Animal Revivon®) is availlable. It has further to be realized that LA Immobilon® is potentially dangerous for personnel, especially when used in remote areas. Therefore, both the specific morphine-antidote for humans (Narcanti®), and trained field personnel should be aboard.
Rea, L. D. and D. P. Costa (1992). Changes in standard metabolism during long-term fasting in northern elephant seal pups (Mirounga angustirostris). Physiological Zooolgy 65( 1): 97-111.
Measurements of body mass, body composition, and O sub(2) consumption rate (V super(.)O sub(2)) were used to quantify some of the factors that influence metabolism during the first 4 mo of development in the northern elephant seal pup (Mirounga angustirostris). During the 4-wk nursing period, average body mass of the pups increased from 42.0 plus or minus 3.5 kg to 127.3 plus or minus 15.9 kg. By the end of the 10-wk postweaning fast mean body mass declined to 83.1 plus or minus 1.5 kg. Body fat increased from 4% of body mass near birth to approximately 48% at weaning but remained relatively constant throughout the fast. Dramatic changes in body mass and body composition such as these would be expected to influence metabolism significantly. To test this theory, O sub(2) consumption was measured in pups from birth to 18 wk of age through open-circuit respirometry. Changes in metabolism were correlated most strongly with increases in lean body mass (r super(2) = .51, P < 0.01). Together, changes in lean body mass and age accounted for 75% of the variability seen in V super(.)O sub(2) (P < 0.01). In addition, a 19% increase in lean mass-specific V super(.)O sub(2) was documented with the onset of feeding in two laboratory animals, after a 10-wk postweaning fast. This implies a depression of metabolism, possibly as an adaptation for energy conservation during long-term fasting.
Rea, L. D. and M. A. Castellini (1995). Adaptations to prolonged fasting in elephant seal pups: plasma chemistry and body mass. World Marine Mammal Science Conference Orlando, Florida, Lawrence, KS, Society for Marine Mammalogy.
Reid, K. and G. A. Nevitt (1998). Observation of southern elephant seal, Mirounga leonina, feeding at sea near South Georgia. Marine Mammal Science 14(3): 637-640.
Reiter, J., N. L. Stinson and B. J. Le Boeuf (1978). Northern elephant seal development: the transition from weaning to nutritional independence. Behavioral Ecology and Sociobiology 3(4): 337-367.
Reiter, J., K. J. Panken and B. J. Le Boeuf (1981). Female competition and reproductive success in Northern elephant seal. Animal Behaviour 29: 670-687.
The probability of weaning a healthy pup increases with age in female northern elephant seals, Mirounga angustirostris . On Ano Nuevo Island, California, weaning success among "prime" females, those 6 years of age or older, was more than double that of "young" females, those 3 to 5 years old. Prime females were better mothers than young females because of superior size, higher social dominance, and greater maternal experience; they were more likely to mate with high-ranking males and gave birth at an optimal time and place, circumstances that maximized the probability that their pups would survive, develop, and reproduce. The competitive advantage of prime-age mothers over younger ones was greatest when female and pup density was high. Young females improved their chances of reproducing successfully by emigrating from crowded harems and establishing new colonies.
Reiter, J. (1984). Studies of female competition and reproductive success in the northern elephant seal. Santa Cruz, California, University of California.
Reiter, J. and B. J. Le Boeuf (1991). Life history consequences of variation in age at primiparity in northern elephant seals. Behavioral Ecology and Sociobiology 28: 153-160.
The age when female northern elephant seals, Mirounga angustirostris , bear their first young varies from 2 to 6 years. At Ano Nuevo, California, a group of 77 females, primiparous at age 3, had a lower survivorship rate to each successive year up to age 8 than a group of 98 females that deferred initial pupping until age 4. The difference in survivorship appears to be due to the greater relative energetic costs of gestation and lactation incurred by the earlier breeding females during a period in their development when growth is rapid. An alternate hypothesis for the difference in survivorship - that young primiparous females are in poor condition from birth - is untenable; females that pupped early in life were larger at weaning age (a correlate of condition) than females that were primiparous 1 year later. Models based on the data show that differential survival of seals that vary in age at primiparity has important consequences for population growth and life history strategies.
Reiter, J. and B. J. Le Boeuf (1995). Analysis of life histories of female northern elephant seals: implications for senescence theory. World Marine Mammal Science Conference Orlando, Florida, Lawrence, KS, Society for Marine Mammalogy.
For female northern elephant seals size and experience enhance reproductive success and reproductive value remains high for many years of a female's life span. Evidence of senescence or terminal investment may give important insights into the life history of such long lived mammals. In this study we examine the reproductive histories of long-lived female northern elephant seals, Mirounpa anpustirostris, in order to assess changes in reproductive effort with successive breeding attempts and age. The sample was composed of 109 known-age females, ages 3 to 19, that gave birth 5 to 15 times during the period, 1975 to 1993. These life histories were analyzed for evidence of senescence in the form of 1) a decline in fecundity and weaning success, 2) a change in weaning mass of pups, and 3) changes in sex ratio of pups. We found that reproductive success, pup mass and sex ratio did not vary systematically with successive breeding attempts.
Reiter, J. (1997). Life history and reproductive success of female northern elephant seals. Princenton, University Press Princeton: i-xix, 1-332 Chapter pagination 46-52.
Reiter, J. and B. J. Le Boeuf (1998). Analysis of life histories of female northern elephant seals: implications for senescence theory. World Marine Mammal Science Conference Monaco, Lawrence, KS, Society for Marine Mammalogy.
In this study we examine the reproductive histories of long-lived female northem elephant' seals, Mirounga angustirostris, in order to assess changes in reproductive effort with successive breeding attempts and age. The sample was composed of 109 known-age females that gave birth 5 to 15 times (from 3-19 years of age) during the period, 1975 to 1993. Variables analyzed were: fecundity, weaning success, mass of pup at weaning and pup sex We found that reproductive success. pup mass and sex ratio did not vary systematically with successive breeding attempts. Though there is much variation in the population in mass of pups at weaning, individual mature females wean pups of similar mass throughout life. These findings have important implications for senescence theory and life history theory.
Ribic, C. A. (1988). Maternal aggression in northern elephant seals: The effect of the pup. Canadian Journal of Zoology 66(7): 1693-1698.
Female northern elephant seals (Mirounga angustirostris ) were observed for three breeding seasons on Southeast Farallon Island to determine the effect of the pup on maternal aggression. Among females that weaned pups in all three seasons, individuals did not win more encounters but differed in percentage of females that moved away and in mean percentage of aggressive encounters started as they aged. A number of variables were associated with an increased probability that a female would successfully wean her pup: early arrival date, having a high percentage of females that moved away, and a high mean percentage of aggressive encounters won.
Keywords: aggressive behavior; maternal behavior; parental behavior; Mirounga angustirostris; pups ER: Environmental Regime Marine
Riedman, M. L. and C. L. Ortiz (1979). Changes in milk composition during lactation in the Northern elephant seal. Physiological Zoology 52: 240-249.
Riedman, M. L. (1982). Studies on the biology and behavior of northern elephant seals with a review on the evolution of fostering behaviors in mammals and birds. Part 1. Alloparental care and adoption in mammals and birds. Part 2. Mother-pup separation and adoption in northern elephant seals. Part 3. Changes in milk composition during lacta in the northern elephant seal.
Riedman, M. L. and B. J. Le Boeuf (1982). Mother-pup separation and adoption in Northern elephant seals. Behavioral Ecology and Sociobiology 11: 203-215.
Riedman, M. L. (1983). Practice makes perfect. The difficult art of mothering in an elephant seal rookery.
Ries, E. H. (1996). [Telemetry of seals: example of applied research.].
Robinson, T. J. and P. R. Condy (1979). The chromosomes of the southern elephant seal, Mirounga leonina (Phocidae: Mammalia).
Rodhouse, P. G., T. R. Arnbom, M. A. Fedak, J. Yeatman and A. W. A. Murray (1992). Cephalopod prey of the southern elephant seal, Mirounga leonina L. Canadian Journal of Zoology 70( 5): 1007-1015.
In the austral summers of 1986 and 1988-1989, 51 southern elephant seals (Mirounga leonina ) at Husvik, South Georgia (54 degree 10'S; 36 degree 43'W), were stomach lavaged after chemical immobilization. Only cephalopod remains were retrieved, including 1070 lower that were identified and measured. In total these were estimated to represent a wet weight of 187.8 kg. Fourteen species of squid from 11 families and 2 species of octopod from 1 family were present. The most important species overall were the squids Psychroteuthis glacialis in terms of numerical abundance (33.7%) and Moroteuthis knipovitchi in terms of estimated biomass (31.2%). The remaining biomass was mainly comprised of the five large muscular squids, Kondakovia longimana (24.0%), P. glacialis (15.4%), Martialia hyadesi (11.2%), Alluroteuthis antarcticus (10.8%), and Gonatus antarcticus (3.6%).
Rodhouse, P. G. (1997). Precautionary measures for a new fishery on Martialia hyadesi (Cephalopoda, Ommastrephidae) in the Scotia Sea: an ecological approach.
Rodriguez, D. H. (1996). [Biology and ecology of pinnipeds of the Buenos Aires region]. Mar Del Plata (Argentina), Facultad De Ciencias Exactas Y Naturales.
A study was conducted regarding the situation of pinniped populations recorded in the Buenos Aires Province of Argentina. The following aspects were covered: descriptions and identifications of different distribution areas of the region; estimations on size, age composition, main numerical variations and social habits of the area sites; studies on population trends of the bonaerense region during the last years; definitions on the type and level of interactions with the fishing activity; role features of the Buenos Aires province in relation to pinniped concentrations from Uruguay and northern Patagonia. This work is the first systematic study of the pinniped group of the bonaerense region and information is given on the presence of seals Hydrurga leptonyx, Mirounga leonina and marine wolves, Arctocephalus australis, Arctocephalus tropicalis, Arctocephalus gazella, Otaria flavescens of the Buenos Aires province during the last 10 years.
Rodriguez, D. and R. Bastida (1998). Four hundred years in the history of pinniped colonies around Mar del Plata, Argentina. Aquatic Conservation: Marine and Freshwater Ecosystems 8(6): 721-735.
Historical records show the area of Mar del Plata (38 degree 05 theta S/57 degree 32 theta W, Argentina) as inhabited by extensive seal colonies; the present study describes the evolution of their size and location from the 16th century to the present. Southern sea lion (Otaria flavescens Shaw 1800), South American fur seal (Arctocephalus australis Zimmerman 1783) and southern elephant seal (Mirounga leonina Linnaeus 1758) colonies, which consisted of between 80000 and 165000 animals, were subject to no commercial harvest, and only small local catches were performed by transient aboriginal groups. During the second half of the 19th century coastal zones were rapidly colonized by man and by the turn of the century, the pinniped rookeries finally disappeared. Such a dramatic decline was not only due to spatial competition with man, but also to the indirect effect of pinniped over-exploitation in other areas of the south-western Atlantic. No seal colonies were recorded in Mar del Plata during the 20th century until the mid sixties, when small non-breeding groups of sea lions and fur seals established themselves in the area. The seal rookeries decline in Mar del Plata provides an interesting example of how human activity may severely affect the conservation of pinniped colonies, even with no direct action through massive catches.
Ronayne de Ferrer, P. A., R. A. Gonzalez Colaso, M. E. I. Marquez, A. R. Carlini, D. F. Vergani and G. A. Daneri (1996). Southern elephant seal (Mirounga leonina) 2. Studies of milk protein fractions by gel electrophoresis. Polar Biology 16(4): 241-244.
Milk protein fractions during various stages of lactation in the southern elephant seal Mirounga leonina were analysed. Twelve milk samples were taken from ten females throughout the lactation period during 1990 and 1991 at Stranger Point, King George Island, South Shetland Islands. Milk samples were subjected to polyacrylamide gel electrophoresis (PAGE). Samples from different days of lactation gave similar qualitative electrophoretic patterns. True protein content was significantly higher (P < 0.05) at the beginning of lactation, and then remained constant until weaning. Caseins and whey proteins each consisted of several protein entities (four and five distinct bands respectively). Casein constituted only about 30 % of the protein nitrogen, the remaining 70 % being derived from whey proteins. There was some variation in concentration of casein and whey proteins as a function of time (P < 0.0.5).
Rose, N. A., C. J. Deutsch and B. J. Le Boeuf (1991). Sexual behavior of male northern elephant seals: 3. The mounting of weaned pups. Behaviour 119(3-4): 171-192.
Up to 50% of weaned northern elephant seal pups, Mirounga angustirostris , present on the Ano Nuevo mainland rookery at the end of the breeding season showed evidence (tooth marks and injuries on the neck) of having been mounted by males. Male-inflicted injuries on weanlings ranged from superficial tooth marks to deep gashes and punctures that bled and exposed the blubber. Most marks were superficial. Approximately 0.5% of all weaned pups died on the rookery from 1969-1990; about 35% of the dead weanlings showed physical evidence that they were killed by males and males were suspected of having killed most of the rest. Males mounting weanlings displayed many behaviors that are characteristic of male sexual behavior toward adult females and most weanlings responded like non-estrous females. Males also mounted conspecific juveniles (one and two years old), although these interactions were relatively infrequent because most juveniles were at sea during the breeding season. Most mounters (91%) were subadult males and were observed to mount weanlings only once in a breeding season. The proximate factors leading to weanling mounts appear to be male sexual inexperience, high libido, limited access to adult females, and stimulus generalization.
Rothery, P. and T. S. McCann (1987). Estimating pup production of elephant seals at South Georgia. Symp. Zool. Soc. Lond. 58: 211-223.
The paper reports the results of a survey to estimate pup production of southern elephant seals (Mirounga leonina) at South Georgia in 1985. The cows ashore were counted at least once during the breeding season at every breeding beach on the island. A mathematical model for the haul-out pattern is developed using detailed counts from 5 other studies. The model enables observed counts to be 'corrected' and thereby used to estimate the size of the haul-out population. When the model was applied to the survey data, an observed maximum total of c. 87,600 breeding cows yielded an estimated total of 102,000 pups. Errors of estimation are evaluated and discussed. Some suggestions for further observations in the field and alternative methods of analysis are put forward.
Ryding, F. N. (1982). Ketamine immobilization of southern elephant seals by a remote injection method. BAS Bulletin 5: 21-26.
Ketamine hydrochloride in intramuscular doses of 4.5-13.6 mg per kg body weight was found to be a useful and satisfactory method of immobilizing male and female Southern elephant seals in order to obtain bacteriological specimens. A simple method of remote injection is described which avoids wastage of Ketamine in the event of the needle being displaced and which enables incremental doses to be given without re-inserting the needle.
S
Sakamoto, W., Y. Naito, A. C. Huntley and B. J. le Boeuf (1989). Daily gross energy requirements of a female northern elephant seal Mirounga angustirostris at sea. Bulletin of the Japanese Society of Scientific Fisheries 55(12): 2057-2063.
Sakamoto, W., Y. H. Naito, A.C. and B. J. Le Boeuf (1989). Daily gross energy energy requirements of female Northern elephant seal Mirounga augustirostris at sea. Nippon Suisan Gakkaishi 55(12): 2057-2063.
Using an energy components analysis of the 73 day continuous time-depth recording of a female northern elephant seal (Mirounga angustirostris ) the total daily energy requirement was estimated to be between 9.4 Mcal and 10.0 Mcal. Total prey energy consumed was estimated between 15.9 and 16.8 Mcal/day, yielding a diet of approximately 10.7 kg of mackerel or 21.0 kg of squid or hake per day. It was estimated that at least 60% of the dives must be successful to account for the mass gained during the period at sea.
Salwicka, K. and K. Sierakowski (1998). Seasonal numbers of five species of seals in Admiralty Bay (South Shetland Islands, Antarctica). Polish Polar Research 19(3-4): 235-247.
Sandegren, F. E. (1976 a). Agonistic behavior in the male Northern Elephant seal. Behaviour 57: 136-158.
Sanvito, S. (1997). Struttura, ontogenesi e funzione dei vocalizzi maschili nell' elefante marino del sud (Mirounga leonina) [Structure, ontogeny and function of male vocalizations in southern elephant seals (Mirounga leonina)]. Departimento di Scienze Naturali. Milano, Italy, Università degli Studi di Milano.
The target of my research project was the structure, development and function of vocalizations of male elephant seals (Mirounga leonina). Due to the current lack of literature on elephant seals sounds I begun with a detailed analysis of the acoustic structure of male vocalizations, with particular attention to sounds used in aggressive contests. I studied the small local population of Sea Lion Island, the main breeding site of elephant seals in the Falklands, during two consecutive breeding seasons (1995 and 1996). Some of the individuals were on Sea Lion both in 1995 and 1996: hence I had an opportunity to record vocalizations of the same male during two seasons and to analyze the ontogenetic process of sound emission. IÕve also analyzed vocalizations recorded at Punta Delgada (Valdes Peninsula), which is one of the closest breeding site of elephant seals. There is a modest exchange of elephant seals between the Valdes and the Falklands but only during the molting season: hence I had an opportunity to compare the acoustic structure of vocalizations between two populations that are part of the same stock but are almost in breeding isolation. I recorded vocalizations from 209 individually recognized males from juveniles to adults, grabbing a total of 30 hours of actual recording: the sample included 85 adults and older subadults. To study the behavioural aspects of sound emission I and three colleagues have done 2522 hours of observation of breeding groups. I realized the most of recordings in standard conditions, being myself the stimulus and at close distance: this recording protocol guaranteed high quality recordings, free from environmental noise. I identified different kinds of sounds emitted in different social contexts: the most important ones are aggressive vocalizations emitted during dominance interactions. Vocal behaviour was the most important component of agonistic behaviour: the vast majority of interactions between males are settled by conventional signalling and vocalizations are the most prominent conventional signals in southern elephant seals. I studied temporal patterning of sounds, their spectrographic structure, and their sound power by mean of direct measurements of sound pressure level; I also studied the macro structure of sound by recognition of syllables and parts of syllable, that is to say sub units of sound with constant and regular structure. Male aggressive sounds were made up by series of well defined individual bouts, each one made up by syllables and parts. The main acoustic features of elephant seals aggressive vocalizations were: train pulses structure, very low frequency (FO Å 25 Hz; fundamental formant Å 250 Hz), scarce frequency modulation and with very high SPL (max = 117 db/1 m). Vocalizations of each individual male were very repeatable: they had an almost constant structure and they were different between males. In analogy with results from the northern species (Mirounga angustirostris) there was a clear ontogenetic trend towards more structured vocalizations. Younger males emitted sounds with large variation in acoustic structure between vocalization series of the same individual. Comparison of sounds of the same individual between seasons, and comparison of individuals of different age classes in each season, demonstrated that ageing trigger a lengthening of vocalizations and bouts, a reduction in frequency of emission and an increase in stereotypy. Notwithstanding large inter individual variation I identified a clear typology in aggressive sounds: sound of most males from both Punta Delgada and Sea Lion Island have been classified in a small number of very recognizable classes (2-4), each one with a very similar syllables composition of sounds of different males. Each population had his own classes of aggressive sounds, very different from the one of the other. Due to the variation in stereotypy of sounds during ontogenesis only sounds from older subadult and adult males could be safely put in classes. Hence the micro structure of aggressive sounds of different males is different but their gross structure is similar. I also begun an evaluation of phenotypical correlates of sound structure of individual males, considering body size, behavioural performance in competition, and mating success. There is a strong correlation between male phenotype and the class of vocalization emitted: males with continuous vocalization were significantly larger, had significantly better performance in competition and monopolized the most of the matings. Differences between single males are more blurred: there was no strong correlation between mean acoustic parameters of individual males and their phenotype. The most of the results from correlation analysis and preliminary results from playback experiments suggest that male vocalizations in southern elephant seals should have both a role in individual recognition and in RHP communication: in particular the first process should be more important in settling contests between mature males, while the second one should be the key of settlement of dominance interactions when the difference in RHP is high, that is to say when males have very different age or size. I wish to begin filling the large gaps leaved from my thesis work in the next future: in particular IÕm well aware that there is a large variation in the quality and structure of sounds emitted by individual males along the season, probably because of variation in internal physiological status and/or social context. Hence during the 1997 breeding season I plan to record the same males at least one time during each of the twelve weeks of the season, and to compare acoustic parameters of individual males between weeks.
Sanvito, S. and F. Galimberti (2000 a). Bioacoustics of southern elephant seals. I. Acoustic structure of male aggressive vocalizations. Bioacoustics 11(4): 259-285.
Southern elephant seal (Mirounga leonina) males have a complex and stereotyped system of access to breeding females. The single most important component of male behaviour is vocal signalling, which is used to settle agonistic encounters in most cases. Most aspects of the breeding biology of the species have been studied in depth, but detailed information about structure of vocalizations is not readily available. Here, we present data about the acoustic structure of aggressive male vocalizations collected in the Falkland Islands, and we compare these data to published data on the northern elephant seals. Our main goal is to describe the structure of sounds as a preliminary and indispensable step towards analysis of their functional significance.
Male vocalizations were low pitch sounds, made up by pulse trains, with scarce frequency modulation: low frequency of emission and high sound pressure level are typical of male vocalizations in Pinnipedia, but they were particularly evident in southern elephant seals, probably due to the unusually large body size. The comparison with published data on northern elephant seals was not very easy, due to differences in acoustic terminology and methodology, but it revealed many similarities between the species.
We also carried on a detailed analysis of variability of different acoustic variables, and we discovered that frequency and intensity measures have lower variability than temporal ones, and should hence be the most effective way to convey information about the individual who emits the vocalization.
Keywords: Southern elephant seal, Mirounga leonina, vocalizations, bioacoustics, spectral analysis, agonistic behaviour, Falkland Islands
Sanvito, S. and F. Galimberti (2000 b). Bioacoustics of southern elephant seals. II. Individual and geographical variation in male aggressive vocalizations. Bioacoustics 11(4): 287-307.
In traditional studies of animal communication individual variability was sometimes considered less relevant than species specific aspects, mostly because the goal was the classifications of sounds in repertories. On the other side, individual variability seems to have a significant role in signal function and evolution. In this paper, we analyze individual variation of structure of aggressive vocalizations of male southern elephant seals, and we compare sounds from our main study population, Sea Lion Island (Falkland Islands), with sounds recorded in the nearby population of the Valdés Peninsula (Patagonia, Argentina).
We firstly analyzed repeatability of acoustic parameters at vocalization and male level. Repeatability of bouts of the same vocalization was extremely high, and this confirmed that vocalization is the fundamental level of organization of male acoustic communication in this species. Also repeatability of vocalizations of individual males was very high, and hence sounds may effectively convey information about identity of the individual who emits the sound.
Male aggressive vocalizations were classified in a small number of types, and each male emitted always the same type of vocalization. We compared the typology of sounds emitted by Sea Lion Island males with vocalizations by Valdés Peninsula males, and we found striking differences. None of the sound types was shared by the two populations, and, although similar in fundamental acoustics, sounds from the two populations had different macrostructure. We conclude that these two populations present dialects in male acoustic communication, although scarcity of recordings from other populations limit the scope of this conclusion.
Keywords: Southern elephant seal, Mirounga leonina, vocalizations, bioacoustics, individual variation, geographic variation, dialects, Falkland Islands, Valdés Peninsula
Sanvito, S. and F. Galimberti (2003). Source level of male vocalizations in the genus Mirounga: repeatability and correlates. Bioacoustics 14: 45-57.
Male vocalisations have an important role in mating tactics, breeding strategies and sexual selection. Most studies of vocalisations are concentrated on the time and frequency domains, while the intensity of sound, an important acoustic parameter that should be related to body size, is almost completely ignored as a possible honest signal of resource holding potential (RHP) and cue for mate choice. In this paper, we analyse the repeatability, the correlations with age and size, and the relationship with breeding status of source level (SL) of male vocalisations in the two species of elephant seals (Mirounga leonina and M. angustirostris). We found a high repeatability of SL, equal or higher than the repeatability of frequency domain parameters estimated in a previous study. Southern elephant seal males were significantly larger and produce significantly more powerful vocalisations than northern males. Moreover, in each species SL was related to age, body size, and breeding status of males, but relationships were weak and accounted for just a small proportion of SL variance. We conclude that, although SL may be an honest signal of gross differences of RHP, it is not, by itself, a good candidate for the transmission of high-resolution information on individual phenotype. A combination of SL and frequency components could be, on the contrary, an effective way to communicate RHP.
Sanvito, S., F. Galimberti, K. M. Delahunty and D. W. McKay (2004). Blood spots in Pinnipedia hormone studies: measure of cortisol levels in southern elephant seals (Mirounga leonina). Aquatic Mammals 30(2): 251-256.
The collection of blood spots on filter paper for hormone analysis has become quite popular in human and primate studies, mostly because of the easiness of handling, storage, and transportation of samples, but has never been tested in wild marine mammals. In this paper, we describe a protocol for the collection of blood spots and the analysis of cortisol in southern elephant seal (Mirounga leonina) weanlings. We demonstrated that cortisol measured in blood spots is very well correlated to cortisol measured in serum samples, and we calculated equations to convert between the two. We describe the possible pitfalls of blood spot analysis protocol, and suggest solutions. The use of blood spots for hormone analysis presents many advantages for field research, may open interesting opportunities like the serial sampling of unrestrained adult individuals, and represents a step towards the reduction of invasiveness of hormone studies.
Sanvito, S., F. Galimberti and E. H. Miller (2004). Vocal learning and cultural transmission in male elephant seals. Submitted to Animal Behaviour.
Sanvito, S., F. Galimberti, C. Braschi and E. H. Miller (2005). Body size and growth in male elephant seals. Journal of Zoology London.
Schneider, R. (1964). Der larynx der Säugetiere. Handbuch der Zoologie, Bd. 8, T. 5, Beitr. 7: 1-128.
Schreer, J. F., R. J. O'Hara Hines and K. M. Kovacs (1998). Classification of dive profiles: a comparison of statistical clustering techniques and unsupervised artificial neural networks. Journal of Agricultural Biological and Environmental Statistics 3(4): 383-404.
Shaughnessy, P. D. (1974). An electrophoretic study of blood and milk proteins of the Southern elephant seal, Mirounga leonina. Journal of Mammalogy 55(4): 796-808.
No electrophoretic variation was found in the blood proteins transferrin, haptoglobin, hemoglobin, LDH, and caeruloplasmin in 97 southern elephant seals from Macquarie Island. Variation was observed in two whey proteins in ten females from the same population. On the assumption that the variation in these whey proteins is genetically controlled, 0.17 of the loci examined are polymorphic, and the proportion of heterozygous loci per individual is 0.075.
Shaughnessy, P. D. (1975). Observations on the seals of Gough Island. S. Afr. J. Anatarctic Res. 5: 42-44.
Two species of seal occur on Gough I.: the subantarctic fur seal Arctocephalus tropicalis and the southern elephant seal Mirounga leonina. The methods and results of observations made on the island between Oct. 16 and Nov. 8, 1973 are presented. Specimens of both species were tagged and blood samples taken for analysis. A count of 13,000 fur seals was obtained in 1956, most of which were on the west coast. A comparison of counts made on some east coast beaches in Nov. 1973 with those made in 1956 at the same locations suggests a twofold increase. The large number of fur seals (185) seen at the Glen suggests that this is a preferred location. The elephant seal population at Gough was estimated at less than 300 in 1956. Forty elephant seals were seen on east coast beaches during the 1973 visit, 38 of them in Hawkins Bay. Observations provide evidence of a breeding population on the island. It was not possible to determine whether the population of elephant seals at Gough I. has changed since 1956.
Shipley, C. (1981). Development of vocalization in northern elephant seal bulls. Los Angeles, California, University of California.
Shipley, C., M. Hines and J. S. Buchwald (1981). Individual differences in threat calls of northern elephant seal bulls. Animal Behaviour 29(1): 12-19.
Shipley, C. O. (1982). Development of vocalization in northern elephant seal bulls. Dissertation Abstracts International B Sciences and Engineering 42(4): 1664.
Shipley, C., M. Hines and J. S. Buchwald (1986). Vocalizations of northern elephant seal bulls: development of adult call characteristics during puberty. Journal of Mammalogy 67(3): 526-536.
Shipley, C. and G. Strecker (1986). Day and night patterns of vocal activity of Northern Elephant Seal bulls. Journal of Mammalogy 67(4): 775-778.
Some species of pinnipeds are known to be active at night. Northern fur seal (Callorhinus ursinus ) bulls sleep for only brief periods during the breeding season (Bartholomew, 1953). The authors observed the behavior of two breeding groups of elephant seals during both light and dark periods. They hypothesized that vocal threats, which are clearly important in maintaining social structure during daylight, might be of increased importance at night when visual cues are reduced. They therefore expected to observe a higher rate of threat vocalization during darkness than daylight.
Shipley, C., B. S. Stewart and J. Bass (1992). Seismic communication in Northern elephant seals. Marine Mammal Sensory System. J. T. e. al. New York, Plenum press: 553-562.
Shoda, L. K. M., W. C. Brown and A. C. Rice-Ficht (1998). Sequence and characterization of phocine interleukin 2. Journal of Wildlife Diseases 34(1): 81-90.
To improve assessment of cellular immune responses in seals, northern elephant seal (Mirounga angustirostris) interleukin 2 (IL-2) has been characterized. The gene was cloned and sequenced from a 658 base pair (bp) cDNA generated from total RNA by reverse transcription-polymerase chain reaction (RT-PCR). The sequence encoded a 154 amino acid (aa) polypeptide that included a 20 aa putative signal peptide. Seal IL-2 was found to share considerable identity with published sequences. Nucleotide sequence analysis of phocine (seal) IL-2 with canine, feline, human, trichechine (manatee), bovine and murine sequences demonstrated 93, 92, 86, 82, 78 and 71% identity, respectively. Analysis of the derived amino acid sequences demonstrated 88, 89, 78, 71, 66 and 60% identity, respectively. Interleukin-2 sequence identities appear to reflect evolutionary proximity among the analyzed species, and importantly, those residues identified as critical to IL-2 biological activity and receptor binding are largely conserved. To examine the kinetics of IL-2 mRNA expression, northern elephant seal lymphocytes were stimulated with the mitogen concanavalin A (Con A), and RNA was collected at several time points thereafter. The RT-PCR demonstrated that seal IL-2 mRNA expression peaks in the first 8 hr following Con A stimulation. Lastly, genomic DNA from northern elephant seal, harbour seal (Phoca vitulina) and California sea lion (Zalophus californianus) was used as template to identify and clone genomic IL-2. Partial sequence of the genomic clones demonstrated nearly complete identity among the three species. Sequence identity indicates that probes constructed from the northern elephant seal IL-2 gene will be effective in assessing IL-2 in other pinniped species.
Skinner, J. D. and R. J. Van Aarde (1983). Observations on the trend of the breeding population of southern elephant seals, Mirounga leonina, at Marion Island. J. Appl. Ecol. 20(3): 707-712.
The annual haulout pattern of adult southern elephant seal cows is described by polynomial functions with differences in the rate of haulout and the asymptote attained resulting in the coefficients and constants of the functions being different. An analysis of data collected during nine breeding seasons from 1973 to 1982 indicated an overall decrease of 11.0 and 8.0% for the adult bull and cow components of the population breeding at Marion Island. The number of cows hauling out to produce pups is exponentially related to the number of adult bulls present on land during the year of fertilization. The overall decrease in the population may therefore be ascribed to factors responsible for a decrease in bull numbers.
Slade, R. W., C. Moritz and A. Heideman (1994). Multiple nuclear-gene phylogenies: application to pinnipeds and comparison with a mitochondrial DNA gene phylogeny. Molecular Biology and Evolution 11(3): 341-356.
Phylogenetic analyses of closely related species should use information from multiple, independent genes with relatively high rates of sequence evolution. To investigate species for which there are few prior sequence data for single-copy nuclear (scnDNA) genes, primers for gene amplification can be designed to highly conserved regions of exons in order to amplify both coding (exons) and noncoding (introns) sequences. We have explored this approach in a phylogenetic analysis of six species of pinnipeds that, together with terrestrial carnivore outgroups, encompass divergence times < or = 40-50 Mya. We sequenced one intron from each of the aldolase A (ALD-A), aldolase C (ALD-C), and histone H2AF genes; one exon from the major-histocompatibility-complex DQA gene; a H2AF processed pseudogene (psi H2AF); and, for comparison with the nuclear genes, the 5' portion of the mitochondrial DNA (mtDNA) control region. The pinniped psi H2AF genes were found to be of limited use because they were paralogous with the gene in the outgroup. The rate of silent substitution in scnDNA (primarily introns) was 5-10-fold lower than that for mtDNA control region I, and scnDNA sequence divergence increased linearly with time < or = 40-50 Mya. Alleles at three polymorphic scnDNA loci (ALD-A, H2AF, and DQA) in the southern elephant seal were paraphyletic with respect to the allele from the closely related northern elephant seal, while the more numerous mtDNA alleles were monophyletic. This we attribute to the consequences of a higher mutation rate rather than to a lower effective population size of mtDNA compared with scnDNA. Within the short (i.e., < 500-bp) sequences of individual scnDNA sequences, phylogenetically informative variation was insufficient to obtain robust phylogenies. However, the combined scnDNA sequences produced a well-supported phylogeny congruent with that derived from mtDNA. This analysis illustrates the high resolution of mtDNA sequences compared with a similar length of scnDNA sequence, but it also demonstrates the utility of combining information from multiple short scnDNA sequences obtained using broadly applicable primers.
Slade, R. W. (1997). Genetic studies of the Southern Elephant Seal Mirounga leonina. Marine Mammal Research in the Southern Hemisphere, Vol.1: Status, Ecology and Medicine. M. H. C.Kemper. Chipping Norton, Surrey Beatty & Sons: 11-29.
Slade, R. W., C. Moritz, A. R. Hoelzel and H. R. Burton (1998). Molecular population genetics of the southern elephant seal Mirounga leonina. Genetics 149(4): 1945-1957.
Southern elephant seals breed on sub-Antarctic islands and have a circumpolar distribution. We assayed mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) variation in the three main populations in the south Atlantic, south Indian, and south Pacific oceans, and a smaller continental population in South America. Population structure of mtDNA was strong and not consistent with isolation by distance. The nDNA loci, although less informative, were consistent with the mtDNA results. Geographic structure appears to be dominated by historical processes, not contemporary gene flow. Uncorrected levels of nucleotide diversity for mtDNA control region I (2.86%) and nDNA (0.09%) were similar to those in humans and mice. Mutation rates for control region I (75 x 10(-9) substitutions per site per year) and nDNA (1.23 x 10(- 9)) were similar to those in other mammals. Female effective population size and total effective population size were roughly equal at approximately 4 x 10(4), indicating a twofold greater rate of drift for mtDNA. Effective breeding sex ratio of four to five females per male was estimated from nucleotide diversity and mutation rates for mtDNA and nDNA, and was much less than behavioral observations would suggest. There was no evidence for selection at any of the assayed loci.
Slip, D. J., H. R. Burton and N. J. Gales (1992). Determining blubber mass in the southern elephant seal, Mirounga leonina by ultrasonic and isotopic techniques. Australian Journal of Zoology 40(2): 143-152.
The mass of subcutaneous fat was determined for 14 male southern elephant seals, Mirounga leonina , by a modified version of a previously described ultrasound model (Gales and Burton 1987). The new model took into account fat slumping and was more accurate than the first model. The accuracy of the new technique was assessed by flensing. Total body water was estimated by tritiated-water dilution, and the relationship between total body water and ultrasonically determined total blubber mass was established. Predictive relationships for total blubber mass, and the relationship between total blubber mass and total body fat were determined. This study has demonstrated the applicability of ultrasound and isotope-dilution techniques in determining the fat composition in vivo of southern elephant seals.
Slip, D. J., N. J. Gales and H. R. Burton (1992). Body mass loss, utilisation of blubber and fat, and energetic requirements of male southern elephant seals, Mirounga leonina, during the moulting fast. Australian Journal of Zoology 40(3): 235-243.
The energetic requirements of male southern elephant seals, Mirounga leonina, were estimated from mass loss, and changes in blubber mass determined by ultrasound in 11 seals over the moulting fast. Mean rate of mass loss was 9.60 plus or minus 2.25 kg/day or 6.46 plus or minus 0.77 g/kg/day, with about 63% of this lost as fat. Blubber was depleted by about 48% over the moulting period. The relative distribution of blubber remained unchanged after the moult, and seals lost blubber at similar rates over all areas of the body. Energy expenditure was estimated to be 7.54 plus or minus 2.82 MJ/kg over the mean 35.6-day moulting period.
Slip, D. J., M. A. Hindell and H. R. Burton (1994). Diving behavior of southern elephant seals from Macquarie Island: an overview. Elephant seals. Population ecology, behavior and physiology. B. J. L. B. R. M. Laws. Berkeley (CA), Un. California Press: 253-270.
Results from 84 deployments of time-depth recorders on southern elephant seals at Macquarie I. are discussed. Water temperature data, also collected by the diving instruments, indicated that the major foraging areas of adult elephant seals from Macquarie I. were located in antarctic waters and that males used areas over the antarctic continental shelf, while females tended to inhabit deeper offshore waters. Approximately 90% of the time at sea was spent submerged, with times on the surface generally less than 10 minutes. Five characteristic dive types were identified, the most common of which were type 1 and type 2 dives. Both types are characterized by rapid descent to a depth followed by a protracted time at that depth interspersed with a number of small "wiggles," in turn followed by a rapid ascent to the surface. Type 1 dives exhibited marked diurnal variation, while type 2 dives showed no such variation and were usually in long sequences of very similar depths. The majority of dives made by southern elephant seals are characteristically deep (maximum depth=1,430 m) and long (maximum duration=120 min.) Estimated aerobic dive limits (ADL) were rarely exceeded by males or postbreeding females, but 44% of all dives made by postmolt (and, therefore, gestating) females exceeded ADL. (Auth. mod.)
Slip, D. J. (1995). The diet of southern elephant seals (Mirounga leonina) from Heard Island. Canadian Journal of Zoology 73(8): 1519-1528.
Stomach contents were lavaged from 76 southern elephant seals (Mirounga leonina) at Heard Island between July 1992 and March 1993. Eighty-six percent of stomachs contained cephalopods of 17 species. Numerically the most important was Psychroteuthis glacialis (21.1%), and from estimated biomass the most important was Kondakovia longimana (40.4%). Three other species were also common prey: Moroteuthis knipovitchi (19.4% by estimated biomass), Moroteuthis ingens (13.0%), and Alluroteuthis antarcticus (10.2%). Sixty-six percent of stomachs contained fish remains, and four species, Dissostichus eleginoides, Electrona carlsbergi, E. antarctica, and Gymnoscopelus nicholsi, were identified from otoliths. The diet of adults differed from that of juveniles, particularly pups in their first year. Martialia hyadesi was the most important prey of juveniles and represented 57.1% of estimated biomass consumed. Furthermore, smaller seals ate smaller squid. The species and size of cephalopods eaten by southern elephant seals are similar to those of other Southern Ocean predators, particularly some beaked whales.
Slip, D. J. and R. Woods (1996). Intramuscular and intravenous immobilization of juvenile southern elephant seals. Journal of Wildlife Management 60(4): 802-807.
We compared intravenous and intramuscular administrations of ketamine and diazepam to immobilize juvenile (8 to 24-month-old) southern elephant seals (Mirounga leonina), to determine the most appropriate method for immobilizing seals to a level required for stomach flushing or attaching electronic activity recorders. With intravenous injections, time to induction was shorter (P < 0.001) and less variable (P < 0.001), the duration of immobilization was shorter (P < 0.001) and less variable (P < 0.003), and dose of ketamine was lower (P < 0.001) and less variable (P < 0.001). Eight of 32 seals (25%) injected intravenously had apneas ranging from 8 to 20 minutes (mean = 16 plus or minus 4.5 min), and 6 of 27 seals (22%) injected intramuscularly were apneic for more than 5 minutes. Seals that became apneic after intravenous injection began breathing before the theoretical aerobic dive limit was reached.
Slip, D. (1997). Diving and foraging behaviour of juvenile southern elephant seals from Heard Island. Hindell, Mark; Kemper: i-x, 1-186 Chapter pagination 114-124.
Slip, D. J., J. Van Der Hoff and H. R. Burton (1998). Energy utilisation and food consumption of southern elephant seal population at Heard and Macquarie islands: potential for competition with commercial fisheries. World Marine Mammal Science Conference Monaco, Lawrence, KS, Society for Marine Mammalogy.
Slip, D. J. and H. R. Burton (1999). Population status and seasonal haulout patterns of the southern elephant seal (Mirounga leonina) at Heard Island. Antarctic Science 11(1): 38-47.
We surveyed the southern elephant seal population at Heard Island regularly from February 1992 to March 1993, and determined the haulout patterns of the major components of the population. While haulout patterns of moulting and immature seals may give broad indices of population trends, the breeding haulout of adult females was the only reliable haulout that could be used to determine annual pup production. During the breeding season 14 277 adult females were counted. Raw counts were corrected using two models, one purely mathematical and the other based on the haulout behaviour of adult female seals. The two models have slightly different assumptions, but both provided good fits to the observed haulout patterns and estimated total population with a coefficient of variation of less than 5%. Total pup production was estimated at between 17 000 and 18 000 for 1992. Previous counts of elephant seals from 111949-51, 1985 and 1987 were corrected using the same models. The two models gave estimates of the population that were within plus or minus 2.5% for all but one year. The population declined by about 50% between 1949 and 1985 but there appears to have been little change from 1985-92. The previous decline may be related to changes in sea-ice.
Keywords: Population characteristics; Population number; Breeding sites; Surveys; Mirounga leonina; PSE, Heard I. ER: Environmental Regime Marine TR: ASFA Input Center Number MB9901000
Sorensen, J. H. (1950). Elephant seals of Campbell Island. Cape Exped. Series Bull. 6: 1-31.
Southall, B. L., R. J. Schusterman and D. Kastak (2000). Masking in three pinnipeds: underwater, low-frequency critical ratios. J Acoust Soc Am 108(3 Pt 1): 1322-6.
Behavioral techniques were used to determine underwater masked hearing thresholds for a northern elephant seal (Mirounga angustirostris), a harbor seal (Phoca vitulina), and a California sea lion (Zalophus californianus). Octave-band white noise maskers were centered at five test frequencies ranging from 200 to 2500 Hz; a slightly wider noise band was used for testing at 100 Hz. Critical ratios were calculated at one masking noise level for each test frequency. Above 200 Hz, critical ratios increased with frequency. This pattern is similar to that observed in most animals tested, and indicates that these pinnipeds lack specializations for detecting low-frequency tonal sounds in noise. However, the individual pinnipeds in this study, particularly the northern elephant seal, detected signals at relatively low signal-to-noise ratios. These results provide a means of estimating zones of auditory masking for pinnipeds exposed to anthropogenic noise sources.
Southall, K. D., G. W. Oliver, J. W. Lewis, B. J. Le Boeuf, D. H. Levenson and B. L. Southall (2002). Visual pigment sensitivity in three deep diving marine mammals. Marine Mammal Science 18(1): 275-281.
Southall, B. L. (2002). Northern elephant seal field bioacoustics and aerial auditory masked hearing thresholds in three pinnipeds. Department of Ocean Sciences. Santa Cruz, California, University of California.
Southall, B. L., R. J. Schusterman and D. Kastak (2003). Acoustic communication ranges for northern elephant seals (Mirounga angustirostris). Aquatic Mammals 29(2): 202-213.
Acoustic communication range estimates for four northern elephant seal (Mirounga angustirostris) vocalization types are presented for this species. Maximum signal detection ranges are determined using an integrated approach involving: field measurements of vocalization source levels and spectral characteristics, signal directivity patterns, natural ambient noise measurements, and previously collected laboratory audiometric data. Signals and masking noise were analyzed using two filter bandwidths believed to approximate the upper and lower limit of auditory filter widths for the northern elephant seal auditory system. Signal detection ranges are estimated for representative pup 'female attraction calls' (FAC), adult female 'pup attraction calls' (PAC), adult female 'threat calls' (AFT), and adult male 'clap threat calls' (AMCT) in each of three intensity categories for biotic noise, wave noise, and wind noise. Signal detection ranges in these nine natural masking noise conditions vary from 5-70 m for FAC, 10-105 m for PAC, 41-479 m for AFT, and 59-507 m for AMCT. The results demonstrate the extent to which communication ranges in the field can vary depending on call type, signal directivity, ambient noise conditions, and receiver capabilities. These data are also useful in considering natural constraints on acoustic communication in northern elephant seals, selective pressures on signal production and reception systems, and potential negative effects of anthropogenic noise.
Stewart, B. S. and P. K. Yochem (1984). Seasonal abundance of pinnipeds at San Nicholas Island, California, 1980-1982.
Seasonal cycles in abundance of northern elephant seal (Mirounga angusitirostris ), California sea lion (Zalophus californianus , Pacific harbor seal (Phoca vitulina richardsi ) and Guadalupe fur seals (Arctocephalus townsendi ) at San Nicolas Island, California, were monitored by frequent ground and aerial surveys from February 1980 through September 1982. Northern elephant seals were most abundant in late January and early February during the height of their breeding season and again in late April to early May when juveniles and adult females hauled out to molt. Sea lions were most abundant in late June to early July during the height of their breeding season and were least abundant in winter and early spring. Harbor seals were in greatest abundance in late May to early June when they were molting and numbers were lowest in winter. Guadalupe fur seals were present from June through September during their breeding season. Seasonal populations and pup production of elephant seals, sea lions, and harbor seals increased each year.
Stewart, B. S. and P. K. Yochem (1986). Northern elephant seals breeding at Santa Rosa Island, California. Journal of Mammalogy 67(2): 402-403.
Stewart, B. S. and R. L. Delong (1993). Seasonal dispersion and habitat use of foraging northern elephant seals. Symp. Zool. Soc. Lond. 66: 179-194.
Stewart, B. S., P. K. Yochem, H. R. Huber, R. L. DeLong, R. J. Jameson, W. J. Sydeman, S. G. Allen and B. J. Le Boeuf (1994). History and present status of the northern elephant seal population. Elephant seals. Population ecology,. B. J. L. Boeuf and R. M. Laws. Berkeley (CA), University of California Press: 29-48.
Stewart, B. S. and R. L. DeLong (1995). Double migrations of the northern elephant seal, Mirounga angustirostris. Journal of Mammalogy 76( 1): 196- 205.
Adult northern elephant seals go to sea twice each year for periods of less than or equal to 8 months during which they range widely in the northern Pacific Ocean. Using new tracking technology, we showed that the species (and individuals) returned to the same foraging areas during postbreeding and postmolt movements, documenting the first double migration for any animal. We also showed segregation by sex during both migrations, the causes of which are unknown. Seals dove continually to depths of 250-550 m during both migrations and travelled linear distances of at least 18,000 (females)-21,000 km (males) during the 250 (males)-300 (females) days they were at sea. These are the longest annual migrations yet recorded for individual mammals. The double migrations apparently are modulated by the requirement for seals to return to land twice each year, to molt and to breed, although the reasons seals favor distant molting sites on the California Channel Islands over island and continental beaches nearer foraging areas are unknown.
Stewart, B. S. (1997). Ontogeny of differential migration and sexual segregation in northern elephant seals. Journal of Mammalogy 78(4): 1101-1116.
Adult northern elephant seals (Mirounga angustirostris) are substantially sexually dimorphic in size and in migratory behavior. Both sexes migrate over vast areas of the North Pacific Ocean during biannual migrations between rookeries in California waters and northern foraging grounds, but adult males segregate from adult females during each of these double migrations. I used satellite-linked radiotelemetry to document the ontogeny of differential migration and sexual segregation as a means to better define the ultimate causal mechanisms of these patterns and to evaluate the potential influence of this sexually dimorphic trait on the magnitude of size dimorphism between sexes in the northern elephant seal. The initial direction of migration (northwesterly from rookeries) was established during the 1st year of life in both males and females. Differential migration and sexual segregation appears to develop during puberty, when growth rates of males are substantially greater than those of females, and those patterns are well established by the time males are 4.5-5 years old. This outcome suggests that the development and proximate cause of sexual segregation of northern elephant seals is more precisely related to differential metabolic needs of males during the period of sexual maturation and accelerated growth rather than to sexual differences in gross energy requirements of adults. Segregation appears to confer to pubescent males survival benefits, which more than compensate for the higher mortality that generally is associated with rapid growth during puberty in other taxa with male-biased, sexual dimorphism. The most parsimonious explanation for the evolution of sexual dimorphism in size in northern elephant seals still appears to be sexual selection (intrasexual competition) acting through differential mating success of males. Moreover, differential, rapid growth during puberty and deferred maturity of males versus females are proximate mechanisms promoting larger size of males as adults. I suggest, however, that natural selection has led to sexually dimorphic migratory patterns and segregation of foraging elephant seals and that the segregation may partially maintain and, indeed, enhance sexual dimorphism in size.
Stewart, B. S. (1997). California pinnipeds: population trends, trans-jurisdictional migrations, and ecological function in large marine ecosystems of the eastern North Pacific Ocean. Stone, Gregory; Goebel: status, trends and issues A symposium of the 127th Annual Meeting of the American Fisheries Society, August 28, 1997, Monterey, California Monterey Bay Aquarium & New England Aquarium, Monterey & Boston 1997 i-vii, 1-179 Chapter pagination 13-21.
Strange, I. (1972). Sealing industries of the Falkland Islands. The Falkland Islands Journal: 13-21.
Sydeman, W. J., H. R. Huber, S. D. Emslie, C. A. Ribic and N. Nur (1991). Age-specific weaning success of northern elephant seals in relation to previous breeding experience. Ecology 72(6): 2204-2217.
We studied the effect of age and previous breeding experience on the probability of successful reproduction in female northern elephant seals (Mirounga angustirostris). Reproductive data, collected over a 12-yr period, were analyzed by multiple logistic regression to describe the functional relationships among the variables. We also examined the relationships among age, experience, date of breeding, and reproductive success to determine if differences in timing explain age-specific productivity. Finally, we investigated the relationship among age, experience, and maternal behavior to determine if correlates of reproductive effort could be related to age- and experience-specific patterns of reproductive success. Reproductive success increased between the maternal ages of 3 and 7 yr and then levelled off, demonstrating an asymptotic relationship. However, the relationship between reproductive success and age, after statistically controlling for previous experience, showed instead that success increased linearly throughout an animal's lifetime. In contrast, after statistically controlling for age, reproductive success was related to experience in a parabolic fashion; success increased with experience for the first few breeding attempts, but declined later in an animal's reproductive lifetime. The effects of experience depended on age: among young animals experience was apparently beneficial, but among old animals greater experience was deleterious. These results suggest experience-related senescence. Timing of breeding was related to experience, rather than age, in a curvilinear fashion; arrival and parturition dates were later for inexperienced and very experienced females, and were earliest for moderately experienced animals. Young animals that gave birth later in the season experienced reduced reproductive success; we observed no such decline in older animals. Thus, among young females, arriving and giving birth earlier each year was adaptive. Aggressiveness and dominance increased with age and experience, but we were unable to separate the effects of age and experience. We contend that the experience-related drop in reproductive success reflects the cost of reproduction. Breeding at a young age and/or continuously appears to result in lower reproductive success later in life. Furthermore, curvature in age-specific reproductive success can be explained by experience-related senescence. This result has general applicability, suggesting that age-related senescence instead may be due to reproductive @'burn-out@'. These results indicate that previous breeding experience and differences in individual quality do not explain the pattern of increasing reproductive success with age in northern elephant seals, and provide indirect support for the hypothesis that animals increase reproductive effort as they age to offset a concomitant decrease in residual reproductive value.
Sydeman, W. J. and N. Nur (1994). Life history strategies of female northern elephant seals. Elephant seals. Population ecology, behavior and physiology. B. J. L. B. R. M. Laws. Berkeley (CA), Un. California Press: 137-153.
Sydeman, W. J. and S. G. Allen (1999). Pinniped population dynamics in Central California: correlations with sea surface temperature and upwelling indices. Marine Mammal Science 15(2): 446-461.
We investigated effects of marine climate variability on pinniped populations and assessed the initial stages of recovery following implementation of the U.S. Marine Mammal Protection Act (MMPA) based on long-term (1973–1997) population surveys at the South Farallon Islands and Point Reyes Peninsula, central California. California sea lions increased over the study period, with peak numbers observed during and after major El Niño events. The rate of increase for California sea lions appears to have decreased in recent years. Steller sea lions decreased at the South Farallon Islands and remain depleted at Point Reyes Peninsula. Harbor seal populations increased in a logistic and non-linear fashion at Point Reyes Peninsula and the South Farallon Islands, respectively. Harbor seals were more abundant at the South Farallon Islands during years of relatively high sea-surface temperature, which may be related to their inability to find sufficient prey in coastal waters under these conditions. Northern elephant seal abundance increased in a logistic fashion over the study period at both the South Farallon Islands and Point Reyes Peninsula; however, productivity at the South Farallon Islands decreased in recent years. Maximum haul-out numbers for elephant seals at the South Farallon Islands increased in the 1970s, maintained an asymptote throughout the 1980s and early 1990s, but recently declined; additional studies are needed to investigate which age classes are associated with this decline. Protection afforded by the MMPA has facilitated partial to full recovery of all populations except for Steller sea lion. Oceanographic relationships do not appear to confound interpretations of population recovery and may help to explain changes in the Steller sea lion population.
T
Tarr, P. W. (1988). A southern elephant seal Mirounga leonina (Linn.) resident on the Skeleton coast, S.W.A./Namibia.
Taylor, R. H. and G. A. Taylor (1989). Re-assessment of the status of southern elephant seals (Mirounga leonina) in New Zealand. New Zealand Journal of Marine and Freshwater Research 23(2): 201-213.
The history, distribution and numbers of southern elephant seals (Mirounga leonina) in the Subantarctic are reviewed. The small populations that breed on Campbell and Antipodes islands, and the very few that occasionally pup on the New Zealand mainland, are part of the larger Macquarie I. stock. A comparison of recent and earlier counts has revealed a 97% reduction in the breeding population at Campbell I. since 1947. There has been a decline in the number and size of breeding harems, and in pup production: from 191 pups in 1947 down to 5 in 1986. Little is known of the Antipodes Is. population but, with 113 pups in 1978, this may now be the main breeding population in New Zealand. Breeding populations at Macquarie I., and at many other locations throughout the subantarctic zone of the Indian and Pacific Oceans, have also recently declined. Reasons for these changes are unknown, but possible causal factors in the marine environment are discussed.
Thompson, D. and M. A. Fedak (1995). Models of maternal investment in phocid seals. World Marine Mammal Science Conference Orlando, Florida, Lawrence, KS, Society for Marine Mammalogy.
Thornton, S. M., S. Nolan and F. M. D. Gulland (1998). Bacterial isolates from California sea lions (Zalophus californianus), harbor seals (Phoca vitulina), and northern elephant seals (Mirounga angustirostris) admitted to a rehabilitation center along the central California coast, 1994-1995. Journal of Zoo and Wildlife Medicine 29(2): 171-176.
In 2 yr of bacteriologic culturing of 297 California sea lions (Zalophus californianus), 154 harbor seals (Phoca vitulina), and 89 northern elephant seals (Mirounga angustirostris) stranded alive along the California coast, the most frequent isolates from inflammatory lesions in live animals were Escherichia coli, Streptococcus viridans, Listeria ivanovii, beta-hemolytic Streptococcus spp., and Enterococcus spp. This is the first report of L. ivanovii isolation from a marine mammal. The common isolates from lung and liver in animals dying during rehabilitation were E. coli, Salmonella spp., Klebsiella spp., Pseudomonas spp., Aeromonas spp., Proteus spp., and Staphylococcus aureus. The most common isolates from brain were Enterococcus spp., E. coli, Klebsiella spp., and Pseudomonas spp. Ocular lesions were seen most often in harbor seals and elephant seals, from which the isolates cultured included Pseudomonas spp., Enterococcus spp., Streptococcus viridans, E. coli, Staphylococcus aureus, Proteus spp., Morganella morganii, Moraxella spp., beta-hemolytic Streptococcus spp., and L. ivanovii. Nine different Salmonella serotypes were isolated from 49 animals; S. newport was the most common. These results should enable those working clinically with these species to make logical decisions in choosing initial antimicrobial therapy.
Thorson, P. H. and B. J. Le Boeuf (1994). Developmental aspects of diving in northern elephant seal pups. Elephant seals. Population ecology, behavior, and physiology. B. J. L. Boeuf and R. M. Laws. Berkeley (CA), Un. California Press: 271-289.
Thorson, P. H. (1995). Development of diving in the northern elephant seal (Mirounga angustirostris). World Marine Mammal Science Conference Orlando, Florida, Lawrence, KS, Society for Marine Mammalogy.
Tierney, T. J. (1977). Disease and injury in the southern elephant seal. Australian veterinary journal 53(2): 91-92.
Disease and injury was recorded in 170 tagged southern elephant seals (Mirounga leonina) on the antarctic continent. Trauma due to interspecific predation was the most common disorder. No small seals were observed with lesions attributable to this in the antarctic population. This finding differs from data recorded in a subantarctic (Macquarie Island) population where seals of all class sizes exhibit lesions due to interspecific trauma. No external parasites were observed in the antarctic population.
Tierney, M., M. Hindell, M.-A. Lea and D. Tollit (2001). A comparison of techniques used to estimate body condition of southern elephant seals (Mirounga leonina). Wildlife Research 28(6): 581-588.
The total body water (TBW) and body condition of 86 female southern elephant seals was estimated from tritiated water (HTO) dilution space analysis. HTO blood samples were analysed using two distillation methods (direct serum counts and evaporative freeze capture) that yielded significantly different estimates. Evaporative freeze capture is recommended for use because it is faster, cheaper, and provides a more precise TBW estimate of dilution space. Estimates of TBW were then compared with those derived from bioelectrical impedance analysis (BIA) and morphometric models. There were significant, positive relationships between TBW and BIA variables, but the level of accuracy was inadequate for BIA to be more useful than the other methods trialled. Morphometric models accurately estimated TBW (kg). Models developed from surface area (SA) (TBW = [SA [] 82.58] - 86.94) and from a combination of mass (M), length (L), and girth (G) (TBW = [(M [] 0.72) + (L [] 5.49) + (G [] 134.94) + 164.36)] provided the most accurate TBW estimates. In contrast, condition indices did not give accurate or reliable estimates of relative body condition.
Torres N, D., P. Cattan A and J. Yanez V (1981). Post-breeding habitat preferences of the southern elephant seal, Mirounga leonina (L.), in Livingston Island (South Shetland Islands), Chile. (Pinnipedia: Phocidae), Instituto Antartico Chileno Serie Cientifica No. 27 1981: 13-18.
Townsend, C. H. (1912). The northern elephant seal, Macrorhinus angustirostris, Gill. Zoologica 1: 159-173.
Trillmich, F., K. A. Ono, D. P. Costa, R. L. DeLong, S. D. Feldkamp, J. M. Francis, R. L. Gentry, C. B. Heath and B. J. le Boeuf (1991). The effects of El Nino on pinniped populations in the eastern Pacific. Ecological Studies 88: 247-270.
Trupkiewicz, J. G., F. M. D. Gulland and L. J. Lowenstine (1997). Congenital defects in northern elephant seals stranded along the central California coast. Journal of Wildlife Diseases 33(2): 220-225.
Eleven cases of congenital anomalies were identified in 210 (5%) juvenile northern elephant seals (Mirounga angustirostris) found stranded along the central California (USA) coast from 1 January 1988 to 31 December 1995. Seven individuals had mild-to-moderate hydrocephalus involving the lateral ventricles bilaterally, or the lateral and third ventricles. Two animals had severe cardiac anomalies: hypoplasia of the right ventricle with overriding aorta, and ventricular septal defect. Other anomalies included single cases of hydronephrosis, focal pulmonary dysplasia, and congenital epidermal angiomatosis. Common intercurrent disease processes were verminous pneumonia and arteritis, verminous enteritis and colitis, and splenic and hepatic hemosiderosis. The more severe anomalies were considered to be the cause of debilitation and stranding. Milder anomalies were found incidentally during routine gross necropsy and histopathologic examination.
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van Aarde, R. J. (1980). Harem structure of the southern elephant seal Mirounga leonina at Kerguelen Island.
Van Aarde, R. J. and M. Pascal (1980). Marking southern elephant seals on Isles Kuerguelen. Pol. Rec. 20: 62-65.
Van Aarde, R. J. (1980 a). Fluctuations in the population of southern elephant seals Mirounga leonina at Kerguelen Island. S. Afr. J. Zool. 15: 99-106.
Van Aarde, R. J. (1980 b). Harem structure of the southern elephant seal Mirounga leonina at Kerguelen Island. Rev. Ecol. 34(1): 31-44.
Information was obtained during the austral summer of 1977. Harem sex ratio was 1 male: 29.97 females while the overall sex ratio for mature animals was 1 male:15.2 females. Mean harem structure (beachmaster: assistant beachmasters: challengers: bachelors: adult cows) was 1:2.54 4.03: 1.29: 1.89: 102.3 135.43 for 375 harems occurring along a 79 km stretch of coastline. Harem size as well as harem structure were influenced by the surface structure of the area where animals breed - the largest harems occurring on sandy beaches, followed by pebble beaches, vegetated humps and cobble beaches. While the tremendous increase in population size on a moderately inhabitated stretch of coastline did not result in a significant change in harem size, a slight increase in population size on a densely populated coastline, resulted in a tremendous increase in harem size and a decrease in the number of harems. A significant density dependent relationship was found between harem size and pup mortality.
van Aarde, R. J. (1984). Aspects of the population biology of the southern elephant seal, Mirounga leonina, at Iles Kerguelen.
van den Hoff, J. (2001). Dispersal of southern elephant seals (Mirounga leonina L.) marked at Macquarie Island. Wildlife Research 28(4): 413-418.
Southern elephant seals marked at Macquarie Island disperse to distant locations where they are sometimes seen during their moult and, for juveniles, a mid-year haul-out period (July-August). Most (87%) of these resighted seals were within 1000 km of Macquarie Island, and most commonly at Campbell Island (700 km to the north-east). The sex and age classes most likely to disperse there were males less than two years old. Male elephant seals of all ages were resighted significantly more often than females, the ratio being 2:1 (P > 0.05). Migration duration tended to increase with the seals' age but migration distance was underestimated from resight observations when compared with known telemetry records. Emigration from the Macquarie Island population appears limited. From the resight effort at Campbell Island during 1995 the maximum proportion of the juvenile population from Macquarie Island to haul-out at Campbell Island was in the order of 0.0053.
van den Hoff, J., H. R. Burton, M. A. Hindell, M. D. Sumner and C. R. McMahon (2002). Migrations and foraging of juvenile southern elephant seals from Macquarie Island with CCAMLR managed areas. Antarctic Science 14(2): 134-145.
van den Hoff, J., H. Burton and R. Davies (2003). Diet of male southern elephant seals ( Mirounga leonina L.) hauled out at Vincennes Bay, East Antarctica. Polar Biology 26: 27-31.
Male southern elephant seals (Mirounga leonina) are the largest of the pinnipeds and their foraging migrations take them from their breeding sites to Antarctica where some remain to moult. During February and March 2000, we stomach lavaged 23 male elephant seals that had migrated to a moult location in the Windmill Islands (66°30'S, 110°30'E) on the Antarctic coast. In the 8 stomachs that contained prey remains, we found beaks from 2 squid species (Alluroteuthis antarcticus, n=2, and Psychroteuthis glacialis, n=9), remains of 1 unidenti.ed benthic .sh species, 16 specimens of Euphausia crystallorophias and 1 mysid species. This is in contrast to the maximum of 17 squid and 4 .sh taxa identi.ed from stomachs sampled at Heard and Macquarie Islands, and the 7 squid taxa identi.ed from seals at King George Island in the South Shetland Islands. Elephant seals appear to be a seasonally important component of the Antarctic marine ecosystem. ‘‘Antarctic’’ squid species, such as P. glacialis, may constitute the most important cephalopod prey for southern elephant seals that forage at high latitudes of the Southern Ocean. If the commercial potential for P. glacialis is realised, there is also potential for competition between the .shery and the seals.
van Wyk, J. (1995). Seals of the Prince Edward Islands. African Wildlife 49( 1): 10- 16.
Two of the three seal species which breed at the Prince Edward group of islands (South African territory) appear to be doing well, but the shrinking population of the third - the massive elephant seal - suggests environmental changes are occurring in the Southern Ocean, making long-term monitoring essential.
Vergani, D. F. and H. J. Spairani (1982). Elefante Marino, 1. Estudio del crecimiento durante la lactanica en el Elefante Marino del Sur, Mirounga leonina Linn (Elephant seals 1. Study of growth until weaning in the southern elephant seal, Mirounga leonina Linn). Buenos Aires, Instituto Antártico Argentino.
The processing of data, obtained in studies of elephant seals at Valdés Peninsula and 25 de Mayo Island, is discussed. Methods were developed for the implementation of a system of data processing which is both quick and efficient. They concern: a census methodology, for qualitative and quantitative population evaluations; and length measurements, to determine the structure of population lengths through the use of a theodolite and trigonometric relationships. To process all the information obtained, 3 programs in FORTRAN IV language were worked out and are presented here.
Vergani, D. F. and H. J. Spairani (1982). (Elephant seal. 1. Studies on growth during lactation of southern elephant seal, Mirounga leonina Linn.).
This work was carried out in Punta Norte, Peninsula Valdes, as the first stage of a study to establish the existing relationships with Antarctic populations. The growth of whelps from birth to weaning was observed, and significant differences were found between males and females, the period of suckling for both being determined. R.J. Hofman (1975) formula for the estimation of weight through volume was aplied and its usefulness for the elephant seal was proven.
Vergani, D. F. (1985). Estudio comparativo de las poblaciones de Antártida y Patagonia del Elefante Marino del Sud , Mirounga leonina (Linneo 1758) y su metodología. Buenos Aires, Instituto Antártico Argentino.
Two breeding colonies of southern elephant seas, Mirounga leonina , one located at Punta Norte, Valdes Peninsula and the other at 25 de Mayo Island, Argentine Antarctica, were compared. The parameters analyzed were: determination of the reproductive seasons; comparison of the population structure and a comparison of the serum protein fractions. Results showed a 35 day lag between the apogees of one population and the other with respect to their reproductive season. There were also different phenotype frequencies in the samples from Antarctica and Patagonia. Finally the optimal doses to immobilize individuals through the use of xilazine hydrochloride were determined.
Vergani, D. F. (1985). Comparative study of populations in Antarctica and Patagonia of the southern elephant seal, Mirounga leonina (Linné, 1758) and its methodology. Buenos Aires, Instituto Antártico Argentino: 1-91.
In the comparison of two reproductive colonies of southern elephant seals, Mirounga leonina, the following phenomena were found: a 35-day time lag between the apogees of one and the other reproductive season; significant differences between the social and population structures of the two colonies; different frequencies of phenotypes in the samples from Antarctica and Patagonia. A newly developed method for estimating the production of pups, which was corroborated through statistical tests, is described. Doses to immobilize specimens of elephant seals, through the use of Xilazone Hydrochloride (Rompun, Bayer) were determined.
Vergani, D. F. and Z. B. Stanganelli (1986). Nuevos métodos para el relevamiento de información en el estudio de las poblaciones de Elefantes Marinos del Sur, Mirounga leonina (New methods for population studies in southern elephant seals Mirounga leonina). Buenos Aires, Instituto Antártico Argentino.
The processing of data, obtained in studies of elephant seals at Valdés Peninsula and 25 de Mayo Island, is discussed. Methods were developed for the implementation of a system of data processing which is both quick and efficient. They concern: a census methodology, for qualitative and quantitative population evaluations; and length measurements, to determine the structure of population lengths through the use of a theodolite and trigonometric relationships. To process all the information obtained, 3 programs in FORTRAN IV language were worked out and are presented here.
Vergani, D. F. and Z. B. Stanganelli (1986). (New methods for information retrieval in the study of the southern elephant seal populations, Mirounga leonina , and its processing using computer programs.).
The development of data processing techniques in order to standardize the information on elephant seal (Mirounga leonina ) populations is described. Only length data of the population and a numerical census of the population are provided. The information was processed using programmes developed in FORTRAN IV.
Vergani, D. F., M. N. Lewis and Z. B. Stanganelli (1988). Observations on haul-out patterns and trends in the breeding population of southern elephant seal at Peninsula Valdes (Patagonia) and Stranger Point (25 de Mayo-King George I.) (SC-CAMLR-VI/BG/36).
Southern elephant seal, Mirounga leonina , populations at Peninsula Valdes (Patagonia) and 25 de Mayo-King George I. were studied during the breeding season from 1979 to 1987. Two main objectives were taken into consideration: haul-out pattern and the female population trend. In both places, the intrinsic population growth rate is positive. In 1982, at Stranger Point, a sharp decrease of the female component of the population was observed (r = -56.54%). The recovery of the population at Stranger Point, and the global increase at Peninsula Valdes, indicate the good condition of these populations.
Vergani, D. F. and Z. B. Stanganelli (1990). Fluctuations in breeding populations of elephant seals Mirounga leonina at Stranger Point, King George Island 1980-1988. Antarctic ecosystems: ecological change and conservation. K. R. Kerry and G. Hempel. Berlin, Springer-Verlag: 241-245.
This chapter presents data on annual fluctuations of the population of elephant seals at Stranger Point between 1980-1988 (excluding 1981). A maximum of 825 breeding cows was recorded in 1980. A decline in the population was observed in 1980-1982 which was followed by annual increments until 1986. A further decrease was observed in 1987. The female component was mainly affected in 1980-1982 (r= -0.575) while the male component was affected in 1987 (r= -0.463). A possible influence of El Niño Southern Oscillation (ENSO) events upon the numerical changes in the studied population is discussed.
Vergani, D. F., Z. B. Stanganelli and D. Bilenca (2001). Weaning mass variation of southern elephant seals at King George Island and its possible relationship with "El Nino" and "La Nina" events. Antarctic Science 13(1): 37-40.
Possible effects of "El Nino" Southern Oscillation (ENSO) components "El Nino" and "La Nina" on populations of southern elephant seals, Mirounga leonina L., are considered in this study. Information on pup weaning mass, collected at King George Island, South Shetland Islands, over a ten-year period (1985-94) was analysed with respect to the occurrence of ENSO and recent research in feeding ecology of this population in the Bellinghausen Sea. Weaning mass of elephant seals was found to be higher during La Nina and a lower during El Nino. Differences in weaning mass between sexes varied in different proportions during El Nino and La Nina. The teleconnection between tropical Pacific anomalies and the Bellinghausen Sea deserves further research, and our results suggest a way to study this phenomenon using data of elephant seal pups weaning mass as indicators of changes in food availability.
Vetter, W. and B. Luckas (2000). Enantioselective determination of persistent and partly degradable toxaphene congeners in high trophic level biota. Chemosphere 41(4): 499-506.
Enantiomer separation of chiral toxaphene components in biological samples was studied by application of different chiral stationary phases based on modified cyclodextrins. Several pairs of enantiomers were resolved on permethylated beta -cyclodextrin ( beta -PMCD), among them 2-endo,3-exo,5-endo, 6-exo,8,8,9,10-octachlorobornane (B8-1412), which was not enantiomerically resolved on tert-butyldimethylsilylated beta -cyclodextrin ( beta -BSCD). The latter column was applied to determine the enantiomer ratios (ERs) of 2-endo,3-exo,5-endo, 6-exo,8,8,10,10-octachlorobornane (B8-1413 or P-26) in brain tissue of three seal species. The ER of B8-1413 (P-26) in brain was virtually racemic as well as those of the two persistent and chiral components of technical chlordane, 1-exo,2,2,4,5,6,7,8,8-octachloro-3a,4,7, 7a-tetrahydro-4,7-methanoindane (trans-nonachlor III or MC 6) and 1-exo,2-endo,3-exo,4,5,6,8, 8-octachloro-3a,7,7a-tetrahydro-4,7,methaoindane (U82). In contrast, B8-1412 and 2-exo,5,5,8,9,9,10,10-octachlorobornane (B8-2229 or P-44) were significantly enantiomerically enriched in several samples of high trophic level biota. 2,2,5,5,8,9,9,10,10-Nonachlorobornane (B9-1025 or P-62), a chlorobornane metabolisable by seals and the presumable precursor of B8-2229 (P-44), was also enantiomerically enriched in seal blubber. These results confirm the assumption that some less persistent toxaphene components may be significantly degraded in biological samples. Enantioselective gas chromatography provides the information that such a degradation is happening by the characteristic change of the ratio of the two enantiomers in the respective tissues.
Vogelnest, L., F. Hulst and R. Woods (1996). The veterinary management of southern elephant seals (Mirounga leonina) at Taronga Zoo.
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Wainstein, M., A. Yamzon, B. J. Le Boeuf and C. L. Ortiz (1995). A comparison of behavioral estimates of reproductive success between northern and southern elephant seals. World Marine Mammal Science Conference Orlando, Florida, Lawrence, KS, Society for Marine Mammalogy.
Wainstein, M., B. J. Le Boeuf, W. Amos, N. Gemmell, C. Campagna and C. L. Ortiz (1998). Mating success and paternity in elephant seals. World Marine Mammal Science Conference Monaco, Lawrence, KS, Society for Marine Mammalogy.
Wainstein, M., B. Le Boeuf, C. Campagna, B. Amos, N. Gemmell and L. Ortiz (1999). Paternity in southern elephant seals (Mirounga leonina). World Marine Mammal Science Conference Wailea, Maui, Hawaii, Lawrence, KS, Society For Marine Mammalogy.
The accurate measurement of reproductive success and verification of mating systems has critical implications for evolutionary, behavioral, and population biology. The purpose of this study was to 1) determine the relationship between the distribution of male southern elephant seal paternity and a variety of behavioral correlates, and 2) assess the accuracy of using detailed mating patterns to predict individual paternities. Research was conducted for two consecutive seasons at 2-3 study harems containing approximately 75 males and 300 females at Peninsula Valde's, Argentina. During year one, mating was observed during all daylight hours for the entire season, and all males that copulated or were regular harem attendees were tissue sampled (n=73). During year two, tissue samples were obtained from approximately 150 returning mothers and their pups. Paternity analyses (n=90) were conducted using microsatellite DNA markers and the statistical package Cervus. ANCOVA revealed two significant patterns: 1) number of paternities increased with increasing rank and estimated number of females inseminated (% copulations x number of females), and 2) number of paternities increased with increasing rank and male attendance (% of days at harem). For individual paternities, there was a significant interaction between male rank and a measure of combined copulation duration. Depending on the quality of female mating records, discriminant analysis models using one to four variables correctly predicted individual paternities with an accuracy of 74 to 81%. These findings suggest that field measures of southern elephant seal mating behavior can accurately predict general distributions of paternity. Similarly, though a variety of factors certainly play a role in fertilization, field observations can have considerable power in predicting individual paternities.
Walker, T. R., I. L. Boyd, D. J. McCafferty, N. Huin, R. I. Taylor and K. Reid (1998). Seasonal occurrence and diet of leopard seals (Hydrurga leptonyx) at Bird Island, South Georgia. Antarctic science 10(1): 75-81.
Seasonal haul-out patterns and diet of individually marked leopard seals (Hydrurga leptonyx) were investigated at Bird I. during the 1983-96 winters. A total of 2956 leopard seal sightings were made, and 121 seals were tagged during the study, mainly between 1993 and 1996. Leopard seals were observed between Apr. and Nov., the mean time between the first and last sightings in each year was 208 d. Between 1993-96, eight seals were resident around the island for more than 100 d, and the longest recorded residence was 130 d. There was considerable inter-annual variation in abundance, with a maximum of 502 sightings during 1994, compared with a minimum of 21 during 1986 and 1989. Antarctic fur seals (Arctocephalus gazella) were the main prey item (58% of kills observed and 53% of scats). Other items included penguins (28% of kills observed and 20% of scats) and fish (24% of scats). Antarctic krill (Euphausia superba), southern elephant seals (Mirounga leonina) and seabirds other than penguins were also present in the diet in small quantities. (Auth. mod.)
Watkins, R. and G. Watkins (1995). Female elephant seal visits Eyre Bird Observatory. Western Australian Naturalist 20(1): 51.
Webb, P. M., R. D. Andrews, D. P. Costa and B. J. Le Boeuf (1998). Heart rate and oxygen consumption of northern elephant seals during diving in the laboratory. Physiological Zoology 71(1): 116-125.
Many techniques have been employed to measure metabolic and cardiovascular changes in diving marine mammals. Each of these methods has its advantages, but the methods also have drawbacks when applied to phocid seals. The aim of this study was to investigate heart rate and metabolic responses to diving in juvenile northern elephant seals that are not associated with forced changes in exercise state, and, secondarily, to investigate whether heart rate could be used as an indicator of metabolic rate in this species. Six seals were allowed to dive freely in a metabolic chamber while simultaneous measurements of heart rate and oxygen consumption were made. Within each dive cycle (dive and surface interval), the seals spent an average of 74% of the time submerged. Mean dive duration was 6.43+/-0.6 (SD) min. Mean oxygen consumption during diving was 3.32+/-0.4 mL O2 min-1 kg-1, a decrease of approximately 26% from baseline values. An inverse relationship was observed between oxygen consumption and the percentage of time spent submerged in each dive cycle. The total amount of oxygen consumed during the surface interval increased with increasing dive duration, while the duration of the surface interval itself did not change, indicating that seals alter the rate of O2 uptake rather than the time spent at the surface. Mean heart rate during diving was 34.5+/-6.2 beats min-1, 36% lower than resting values. Mean diving heart rate was independent of dive duration, percent time submerged, and oxygen consumption. Mean surface interval heart rate was 66.6+/-11.1 beats min-1 and was not correlated with oxygen consumption. Average heart rate over the entire dive cycle increased with increasing oxygen consumption in all of the seals, but there was only a significant relationship in two seals, which casts some doubt on the usefulness of heart rate as an indicator of metabolic rate in this species. While providing important information on the changes in heart rate and oxygen consumption during diving in northern elephant seals, a complete understanding of the diving metabolic rate of these animals will require a combination of approaches that can be used in concert with data on freely living animals.
Webb, P. M., D. E. Crocker, S. B. Blackwell, D. P. Costa and B. J. Le Boeuf (1998). Effects of buoyancy on the diving behavior of northern elephant seals. Journal of Experimental Biology 201(16): 2349-2358.
Marine mammals experience radical seasonal changes in body composition, which would be expected to affect their buoyancy in the water, The aim of this study was to examine the relationship between such changes in buoyancy and diving behavior in northern elephant seals Mirounga angustirostris. This was achieved by modifying the buoyancy of 13 juvenile elephant seals translocated from Ano Nuevo State Reserve, CA, USA, and released at various sites in Monterey Bay, CA, USA. The buoyancy of each seal was calculated and was increased or decreased using syntactic foam or lead weights, and their diving behavior was recorded as they returned to Ano Nuevo, The seals were divided into three groups: increased buoyancy (B+), reduced buoyancy (B-) and control seals (Bc), Mean descent rates were 0.77+/-0.3 m s(-1) for the B+ seals, 0.82+/-0.2 m s(-1) for the control seals and 0.87+/-0.3 m s(-1) for the B- seals, and were significantly different. Mean ascent rates for the three treatments were 0.82+/-0.3 m s(-1) for the B+ seals, 0.86+/-0.3 m s(-1) for the control seals and 0.82+/-0.3 m s(-1) for the B- seals, All the B+ seals ascended faster than they descended, while four of the five B- seals descended faster than they ascended. There was a significant negative correlation between buoyancy and descent rate, with less buoyant seals descending faster than more buoyant seals. There was, however, no correlation between ascent rate and buoyancy. This suggests that seals may use negative buoyancy to drift passively during descent, but that all seals may swim continuously during ascent. There was a significant correlation between buoyancy and the drift descent rate of C-type drift dives, including upwards drift in the most buoyant seal. Buoyancy was not correlated with diving depth, trip duration, dive duration or surface-interval duration. This study demonstrates that buoyancy plays a significant role in shaping diving behavior in northern elephant seals and that elephant seals may adjust their behavior to suit their buoyancy, rather than adjusting their buoyancy to suit a dive, This study also validated the truncated cones method of calculating body composition in this species by comparing it with body composition determined using tritium dilution.
Weber, D. S., B. S. Stewart, J. C. Garza and N. Lehman (2000). An empirical genetic assessment of the severity of the northern elephant seal population bottleneck. Current Biology 10(20): 1287-1290.
A bottleneck in population size of a species is often correlated with a sharp reduction in genetic variation. The northern elephant seal (Mirounga angustirostris) has undergone at least one extreme bottleneck, having rebounded from 20-100 individuals a century ago to over 175,000 individuals today. The relative lack of molecular-genetic variation in contemporary populations has been documented, but the extent of variation before the late 19th century remains unknown. We have determined the nucleotide sequence of a 179 base-pair segment of the mitochondrial DNA (mtDNA) control region from seals that lived before, during and after a bottleneck low in 1892. A `primerless' PCR was used to improve the recovery of information from older samples. Only two mtDNA genotypes were present in all 150+ seals from the 1892 bottleneck on, but we discovered four genotypes in five pre-bottleneck seals. This suggests a much greater amount of mtDNA genotypic variation before this bottleneck, and that the persistence of two genotypes today is a consequence of random lineage sampling. We cannot correlate the loss of mtDNA genotypes with a lowered mean fitness of individuals in the species today. However, we show that the species historically possessed additional genotypes to those present now, and that sampling of ancient DNA could elucidate the genetic consequences of severe reductions in population size.
Weber, D. S., B. S. Stewart, J. Schienman and N. Lehman (2004). Major histocompatibility complex variation at three class II loci in the northern elephant seal. Mol Ecol 13(3): 711-8.
Northern elephant seals were hunted to near extinction in the 19th century, yet have recovered remarkably and now number around 175,000. We surveyed 110 seals for single-strand conformation polymorphism (SSCP) and sequence variation at three major histocompatibility (MHC) class II loci (DQA, DQB and DRB) to evaluate the genetic consequences of the population bottleneck at these loci vs. other well-studied genes. We found very few alleles at each MHC locus, significant variation among breeding sites for the DQA locus, and linkage disequilibrium between the DQB and DRB loci. Northern elephant seals are evidently inbred, although there is as yet no evidence of correlative reductions in fitness.
Webster, S. A. and R. W. Baird (1998). Aquatic interactions between a northern elephant seal and humans at Isla Los Islotes, B.C.S., Mexico. Marine Mammal Science 14(1): 202-203.
White, F. N. and D. K. Odell (1971). Thermoregulatory behaviour of the northern elephant seal, Mirounga angustirostris. Journal of Mammalogy 52: 758-774.
Wilkinson, I. S. and M. N. Bester (1988). Is onshore human activity a factor in the decline of the southern elephant seal. South African Journal of Antarctic Research 18(1): 14-17.
Comparison of areas of high and low human activity on Marion I. shows no difference in rates of decline of elephant seal numbers. Spatial distribution of births also shows no change in the period 1976-1986, suggesting that no shift in breeding population distribution has occurred in the period as a result of the level of human activity on Marion I. Furthermore, comparisons of Marion I. with other breeding sites of elephant seals, where human activity is lower, show no significant differences in the rates of decline of the species. Direct onshore human disturbance is therefore rejected as a significant factor in the decline of the species.
Wilkinson, I. S. and M. N. Bester (1990). Duration of post-weaning fast and local dispersion in the southern elephant seal, Mirounga leonina, at Marion Island. Journal of Zoology London 222: 591-600.
Post-weaning behaviour of southern elephant seals, Mirounga leonina , was studied at Marion Island. Duration of fast in both sexes increased in direct proportion to weight at weaning, while it decreased with weaning data in males. Both sexes appear to fast until they have reached a lower weight "threshold" of around 70% of weaning weight. Local dispersion after the fast was studied by resighting tagged animals at weekly intervals. Only 460 (7 multiplied by 0%) resights out of 6530 involved a move between sites, representing 378 (16 multiplied by 8%) of the 2246 pups that were tagged. Males moved more frequently between tagging sites and covered greater distances than females. Moves between sites are more frequent and distances travelled are greater in December than November. Differences in dispersion patterns between Marion Island and Iles Kerguelen may be caused by differences in coastal configuration. Underyearlings spent 105 multiplied by 0 plus or minus 19 multiplied by 6 days at sea before returning for between 10 and 20 days in the autumn.
Wilkinson, I. S. and M. N. Bester (1997). Tag-loss in southern elephant seals, Mirounga leonina, at Marion Island. Antarctic Science 9(2): 162-167.
Rates of tag-loss are determined for Dalton Jumbo Rototags applied to the hind flippers of 4343 (2208 males, 2135 females) southern elephant seal (Mirounga leonina) pups at Marion Island over an eight year period from 1983-1990 as part of a demographic study of the species. Loss rates were the lowest recorded to date for this species (range 0.0-9.1%). No significant relationship existed between age and rate of tag-loss, neither was there any sex or year related differences in age-specific tag-loss rates. The low rates of loss highlight the value of tagging as a marking technique, and allow for high levels of confidence in the reliability of the population parameters that are derived from the tagging data collected for the Marion Island population.
Wilkinson, I. S. and R. Van Aarde (1999). Marion Island elephant seals: the paucity-of-males hypothesis tested. Canadian Journal of Zoology 77(10): 1547-1554.
The southern elephant seal, Mirounga leonina, population at Marion Island has declined since the start of research activities there in 1973, as have populations at other Indian Ocean breeding sites. One suggested mechanism for the decline at Marion Island is a shortage of males, resulting in low insemination rates. We tested this "paucity-of-males" hypothesis by looking at (i) adult sex ratios, (ii) male sexual activity, and (iii) the relationship between levels of sexual activity and the probability of a cow pupping in the following season. Sex ratios were similar to those at other sites where populations are either stable (South Georgia) or increasing (Peninsula Valdes). Dominant bulls monopolised mating opportunities, achieving 98.1% of 629 observed copulations over three seasons. Of the 138 cows coming ashore, only 4 (2.9%) were not seen mating and 89% copulated with only one bull; dominant bulls copulated with all but 1 of the 134 (99.3%) cows that did mate. Cows were mated more frequently than at sites with stable and increasing populations. There was no difference in the observed level of sexual activity between cows seen pupping in the following season and those who failed to pup. This indicates that bulls monopolising harems are capable of inseminating all the cows. Such findings refute the paucity-of-males hypothesis.
Wilkinson, I. S. and R. J. van Aarde (2001). Investment in sons and daughters by southern elephant seals, Mirounga leonina, at Marion Island. Marine Mammal Science 17(4): 873-887.
The southern elephant seal, Mirounga leonina, exhibits extreme sexual dimorphism and polygyny and is thought to be an ideal subject to test maternal investment theory. Predictions concerning differential investment in offspring by sex were tested on M. leonina breeding at Marion Island over three austral summers. Large females produced more male pups, while small females produced more female pups, providing tentative support for the Trivers and Willard (1973) hypothesis. Maternal size had a greater influence on growth rate and weaning mass than on the sex of offspring. Differential reproductive costs to adult females were not evident in terms of future fecundity or survival. In keeping with other studies on this species, we could not demonstrate any differential investment in the two sexes. We suggest that before discounting maternal investment theories, further studies need to be undertaken to determine the benefits, if any, of size at weaning on long-term survival and reproductive success.
Williams, T. M., R. W. Davis, L. A. Fuiman, J. Francis, B. J. Le Boeuf, M. Horning, J. Calambokidis and D. A. Croll (2000). Sink or swim: strategies for cost-efficient diving by marine mammals. Science 288(5463): 133-136.
Locomotor activity by diving marine mammals is accomplished while breathholding and often exceeds predicted aerobic capacities. Video sequences of freely diving seals and whales wearing submersible cameras reveal a behavioral strategy that improves energetic efficiency in these animals. Prolonge gliding (greater than 78% descent duration) occurred during dives exceeding 80 meters in depth. Gliding was attributed to buoyancy changes with lung compression at depth. By modifying locomotor patterns to take advantage of these physical changes, Weddell seals realized a 9.2 to 59.6% reduction in diving energetic costs. This energy-conserving strategy allows marine mammals to increase aerobic dive duration and achieve remarkable depths despite limited oxygen availability when submerged.
Williams, E. E., B. S. Stewart, C. A. Beuchat, G. N. Somero and J. R. Hazel (2001). Hydrostatic-pressure and temperature effects on the molecular order of erythrocyte membranes from deep-, shallow-, and non-diving mammals. Canadian Journal of Zoology 79(5): 888-894.
Little is known about the cellular mechanisms involved in the tolerance of deep-diving marine mammals to hydrostatic pressures that cause serious pathologies when experienced by other mammals. We compared fatty-acid composition, cholesterol content, and the effects of pressure on the molecular order of erythrocyte membranes from deep-, shallow-, and non-diving mammals to determine how these properties may be related to diving performance. Erythrocytes were collected from two deep-diving phocid pinnipeds (northern elephant seal (Mirounga angustirostris) and harbor seal (Phoca vitulina)), a relatively shallow-diving otariid pinniped (northern fur seal (Callorhinus ursinus)), and several nondiving terrestrial mammals (dog (Canis familiaris), horse (Equus caballus), and cow (Bos taurus)). Fatty-acid composition clearly distinguished the phocids from the other species. The monoene content of erythrocyte membranes was substantially lower (3 vs. [apprxeq]20%), whereas the lipid unsaturation indices, the ratio of [alpha]- to [gamma]-linolenic acids, and the proportions of long-chain polyunsaturated fatty acids were substantially higher in the phocids. The cell-membrane cholesterol content was also significantly lower in erythrocytes from the deep-diving phocids (cholesterol:phospholipid ratios 0.2-0.3) than from most other mammals (1.0). Membranes from the phocids were more ordered than those from the shallow- and non-divers, and were also more sensitive to changes in pressure and temperature. The physiological significance of these differences in cell-membrane structure, which affect the order and sensitivity of cell membranes to hydrostatic pressure, is unknown, but they may be important adaptations that allow repeated and prolonged exposure to great hydrostatic pressure.
Williams, T. M. (2001). Intermittent swimming by mammals: a strategy for increasing energetic efficiency during diving. American Zoologist 41(2): 166-176.
The evolutionary history of marine mammals involved marked physiological and morphological modifications to change from terrestrial to aquatic locomotion. A consequence of this ancestry is that swimming is energetically expensive for mammals in comparison to fish. This study examined the use of behavioral strategies by marine mammals to circumvent these elevated locomotor costs during horizontal swimming and vertical diving. Intermittent forms of locomotion, including wave-riding and porpoising when near the water surface, and prolonged gliding and a stroke and glide mode of propulsion when diving, enabled marine mammals to increase the efficiency of aquatic locomotion. Video instrumentation packs (8-mm camera, video recorder and time-depth microprocessor) deployed on deep diving bottlenose dolphins (Tursiops truncatus), northern elephant seals (Mirounga angustirostris), and Weddell seals (Leptonychotes weddellii) revealed exceptionally long periods of gliding during descent to depth. Glide duration depended on depth and represented nearly 80% of the descent for dives exceeding 200 m. Transitions in locomotor mode during diving were attributed to buoyancy changes with compression of the lungs at depth, and were associated with a 9-60% reduction in the energetic cost of dives for the species examined. By changing to intermittent locomotor patterns, marine mammals are able to increase travelling speed for little additional energetic cost when surface swimming, and to extend the duration of submergence despite limitations in oxygen stores when diving.
Wilske, J. and T. Arnbom (1996). Seasonal variation in vitamin D metabolites in southern elephant seal (Mirounga leonina) females at South Georgia. Comparative Biochemistry and Physiology A 114A(1): 9-14.
Southern elephant seals spend two periods on land each year, during breeding and moult, exposed to intensive UV radiation. The time between periods on land are spent at sea, with little exposure to the sun. A study of serum 25-OH-D3 and 1.25(OH)2-D3 on southern elephant seals was carried out at South Georgia. Samples were collected on four different occasions: early and late breeding, and early and late moult. The levels of 25-OH-D3 increased when seals were on land, and decreased when at sea. Two annual peaks of 25-OH-D3 were found, both of which immediately followed periods of intensive exposure of UV radiation. 1.25(OH)2-D3 levels showed a seasonal variation, but no significant changes while seals were on land were detected. The diving behavior at sea for southern elephant seals and no detectable change in 25-OH-D3 indicates that the seals feed on prey containing vitamin D.
Woods, R., S. McLean, S. Nicol and H. Burton (1994). Use of midazolam, pethidine, ketamine and thiopentone for the restraint of southern elephant seals (Mirounga leonina). Veterinary Record 135(24): 572-577.
Thirty-two pre-moulting female southern elephant seals (Mirounga leonina) were heavily sedated with midazolam (0.04 mg/kg) combined with pethidine (4 mg/kg). This combination made it possible to give the seals intravenous injections and was rapidly antagonised by naloxone. After sedation with midazolam and pethidine, 2 to 3 mg/kg intravenous thiopentone or ketamine induced light immobilisation for approximately five minutes and allowed the animals to be intubated. Prolonged deep levels of restraint were achieved after sedation with midazolam and pethidine by repeated intravenous doses of approximately 1.5 mg ketamine/kg at 10 minute intervals, to maintain restraint for 60 minutes.
Woods, R., S. McLean, S. Nicol and H. Burton (1994). A comparison of some cyclohexamine based drug combinations for chemical restraint of Southern Elephant seals (Mirounga leonina). Marine Mammal Science 10(4): 412-429.
This study compared the effects of drug combinations commonly used for chemical restraint of southern elephant seals. The combinations were: ketamine and diazepam, ketamine and midazolam, ketamine and xylazine, and tiletamine and zolazepam. The main aims were to gather basic information regarding the response of the animals to the different combinations, and to determine which were most useful for routine chemical restraint. All drug combinations could be used safely although apnea and whole-body shaking occurred with each. There were significant differences in several of the responses measured. Poor muscle relaxation and prolonged apnea were associated with ketamine and diazepam use. Animals given ketamine and xylatine were more depressed, took longer to recover, had a higher incidence of thermoregulatory problems, and lower heart rate than after other combinations. Ketamine and midazolam and tiletamine and zolazepam produced fewer complications than the other drug combinations, and tiletamine and zolazepam showed greater predictability of response and ease of use, making it preferable for use by people with little experience in anesthesia of elephant seals.
Key words: southern elephant seal, Mirounga leonina, chemical restraint, anes- thesia.
Woods, R. (1994). Chemical restraint of southern elephant seals (Mirounga Leonina); use of medetomidine, ketamine and atipamezole and comparison with other cyclohexamine-based combinations, University of Tasmania.
Woods, R., S. McLean, S. Nicol and H. Burton (1995). Antagonism of some cyclohexamine-based drug combinations used for chemical restraint of southern elephant seals (Mirounga leonina). Australian Veterinary Journal 72(5): 165-171.
This study examined the use of 4 antagonists of chemical restraint in mature female southern elephant seals (Mirounga leonina) that were restrained with ketamine and diazepam, ketamine and xylazine, or tiletamine and zolazepam. The antagonists were: 4-aminopyridine, yohimbine, doxapram and sarmazenil. The effects of the antagonists on the animal's time to first movement forward and recovery, heart rate, respiratory rate and venous blood gas and pH values, and level of chemical restraint were recorded. Sarmazenil (1.0 mg/kg) and doxapram (5.0 mg/kg) partially antagonised 50:1 ketamine: diazepam (ketamine = 3.0 mg/kg, diazepam = 0.06 mg/kg) and tiletamine and zolazepam (tiletamine = 0.5 mg/kg, zolazepam = 0.5 mg/kg). However, the rapid recovery after low doses of anaesthetics means that antagonism is usually unnecessary, and it may increase the likelihood of shaking. Routine antagonism of ketamine and xylazine (ketamine = 3.0 mg/kg, xylazine = 0.5 mg/kg) is more useful given its usually delayed recovery time and potential for thermoregulatory problems. For this purpose yohimbine (0.06 mg/kg) offered advantages over doxapram in giving a smoother recovery with less aggression. 4-aminopyridine (0.2 mg/kg) prolonged chemical restraint by 100:1 ketamine:diazepam (ketamine = 3.0 mg/kg, diazepam = 0.03 mg/kg) and ketamine and xylazine, and should be contraindicated. Doxapram (5.0 mg/kg) was the most useful general antagonist for all groups of drugs but shaking was seen and a lower dose is recommended.
Woods, R., S. McLean, S. Nicol, D. J. Slip and H. R. Burton (1996). Use of the respiratory stimulant doxapram in southern elephant seals (Mirounga leonina). Veterinary Record 138(21): 514-517.
The use of doxapram to stimulate breathing was examined in southern elephant seals chemically restrained with ketamine and xylazine. Animals which were breathing spontaneously received doxapram (approximately 0.5, 1, 2, or 4 mg/kg) or saline into the extradural intravertebral vein. Doxapram caused a dose-dependent increase in the depth and rate of respiration which began within one minute, peaked after two minutes and lasted for up to five minutes. A dose of 2 mg/kg appeared to be safe and effective for the stimulation of respiration, while 4 mg/kg caused arousal and shaking. Doxapram (2 mg/kg) was tested on 14 occasions in animals which had developed apnoea during chemical restraint. Doxapram had no effect when administered into the extradural intravertebral vein and appeared to be of more benefit when administered directly into the lungs via an endotracheal tube, but it was not effective in all cases. There was evidence to suggest that the endotracheal tube prevented some of the animals from breathing. The effect of intubation and endotracheal doxapram administration was therefore examined in 19 apnoeic and 31 spontaneously breathing seals. Intubation induced apnoea in animals at low levels of chemical restraint and endotracheal doxapram was unreliable for the stimulation of breathing.
Woods, R., S. McLean, S. Nicol and H. Burton (1996). Chemical restraint of southern elephant seals (Mirounga Leonina); use of medetomidine, ketamine and atipamezole and comparison with other cyclohexamine-based combinations. Br. Vet. J. 152(2): 213-224.
A study was conducted to assess the effectiveness of the alpha-2 agonist medetomidine for sedation of pre-moulting, mature female southern elephant seals (Mirounga leonina). Two animals were sedated with a single intramuscular dose of medetomidine (0.013 and 0.027 mg kg- 1). A further two groups of five animals received medetomidine (0.017 mg kg-1) combined with ketamine (1.90 mg kg-1) and, 20 min later, either saline or the alpha-2 antagonist atipamezole (0.04 mg kg-1) intravenously. Medetomidine alone did not give sufficient restraint to permit intravenous access. The response appeared to be similar to previous findings with ketamine and xylazine. Administration of atipamezole had little effect upon the level and timecourse of restraint. Ketamine and medetomidine seem to offer few advantages over ketamine and xylazine or other cyclohexamine-drug combinations for routine chemical restraint of southern elephant seals.
Woods, R., S. McLean and H. R. Burton (1999). Pharmacokinetics of intravenously administered ketamine in southern elephant seals (Mirounga leonina). Comparative Biochemistry and Physiology C Pharmacology Toxicology and Endocrinology 123C(3): 279-284.
Worthy, G. A. J., P. A. Morris, D. P. Costa and B. J. Le Boeuf (1992). Moult energetics of the northern elephant seal (Mirounga angustirostris). Journal of Zoology London 227(2): 257-265.
Northern elephant seals, Mirounga angustirostris , undergo an annual moult during which they shed all of their pelage and underlying epidermis. Moulting takes place on land and lasts a mean of 32.0 plus or minus 6.6 days. During this time the mean mass loss of adult females was 24.7 plus or minus 6.1%. Mean body composition at arrival (25.6 plus or minus 4.8% fat) did not differ significantly from that at departure (24.9 plus or minus 3.2% fat). Fat catabolism accounted for 93.6% of derived energy and 41% of mass lost. Approximately 3.5% of total mass loss was associated with the shedding of the pelage and epidermis. Moulting female northern elephant seals express an average daily metabolic rate of 2.0 plus or minus 0.6 times that predicted for adult terrestrial mammals. This energy demand was met by losing 3.0 kg/d of total body mass. These energy expenditures suggest that, similar to data for harbour seals, the moult period is a time of relatively low energy expenditure.
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Zenteno-Savin, T. and M. A. Castellini (1998). Plasma angiotensin II, arginine vasopressin and atrial natriuretic peptide in free ranging and captive seals and sea lions. Comparative Biochemistry and Physiology C Pharmacology Toxicology and Endocrinology 119C(1): 1-6.
Zenteno-Savin, T. and M. A. Castellini (1998). Changes in the plasma levels of vasoactive hormones during apnea in seals. Comparative Biochemistry and Physiology C Pharmacology Toxicology and Endocrinology 119C(1): 7-12.