Southern elephant seal biology

Southern elephant seals (Pinnipedia: Focidae: Mirounga leonina Linneo 1758) are marine mammals strongly adapted to diving. During their yearly life cycle they spent the most of the time at sea, and they come back to land just for breeding and molting. Breeding males usually come to land well before the haul out of the first female and stay on land for up to three months and more. Mature females stay on land during the breeding season for about one month: during this period they give birth, suckle the pup (mean length of lactation is about 21 days), come into oestrus, copulate and go back to the sea. Apart from a period of about 25 days in which they stay on land for moulting, they spend the rest of their life cycle doing continuous deep dives (up to more than one thousand meters deep) to get enough food to recover from the huge drop in weight and energy reserves they sustain during lactation.


Southern elephant seals

Elephant seal male, female, and pup  

During the breeding season females gather in groups of variable size (from 2 to more than 300) traditionally called harems: usually one adult male is in charge of each harem, keeping away the other males and doing the most of the copulations.

Some aspects of southern elephant seals biology are particularly interesting:

Sexual dimorphism (southern elephant seal)

Growth of the proboscis (same male, 5 to 12 years of age)

Annual cycle

Female weigth loss

Weight loss: pregnant female just arrived on land (top) and emaciated female at the end of the suckling, just about to go back to sea

Harem from the air

A medium sized harem from the air (south beach of Sea Lion Island)