Southern elephant seal  (Mirounga leonina)

Instantly recognisable by the large, inflatable proboscis, the southern elephant seal is the biggest seal in its family. Males are up to five times larger than females, and have much larger canines. Both sexes have robust bodies, thick necks and broad heads. The fore flippers have a large, black nail. Adults have a grey-brown coat, and males develop a chest shield of thickened, creased and heavily scarred skin as they age. They also become paler across the face, proboscis and head with age (2). Pups are black when born and have yet to grow the waterproof coat they will need to enter the sea. During the breeding season, southern elephant seals become stained rusty orange and brown from lying in their own excrement (3).

The southern elephant seal is found throughout the southern oceans during the non-breeding season, but in the breeding season, it splits into three discrete populations on islands north of the Antarctic's pack ice. The main islands to support the breeding seals are South Georgia, near the southern-most tip of South America, Macquarie Island, 1,500 km south-south-east of Tasmania, and Kerguelen Island, midway between Africa, Antarctica and Australia (1).

Inhabits the open ocean during the non-breeding season, diving to depths of up to 600 m (4). During the breeding season, the southern elephant seal is found on beaches and rocky terrain (2).

In September to November each year, southern elephant seals return from the open ocean to their breeding grounds to give birth and mate. Males arrive before the pregnant females and wait for their arrival. Once on land, the non-receptive females are harassed by aggressive males who want to mate. To avoid these males, the females collect together into groups known as harems, where a dominant alpha male will protect them from other males, gaining exclusive mating access once they have given birth. Gestation lasts 50 weeks and females give birth to one, or occasionally two pups, which are weaned after a month, and looked after for a further two weeks. They recognise their mothers through calls and smell, but if they are lost even for a short time, they are usually abandoned and will die (1). At three months old, the pups take to the sea for the first time (1).

Just three days after giving birth, females will mate again. The dominant male should be able to mate with all the females in his harem, but the loss of condition suffered whilst defending his females may cause him to lose his position. Bachelor males have no harem and try to invade the harems of other males. Young and small males have so little dominance they are not able to get on land, and try to mate with females as they enter the water (1). After mating, both male and female seals return to the sea to feed again. They return to moult for 30 to 40 days in January and February, during which time they do not feed, and may lose a large amount of weight (4).

Southern elephant seals make fairly deep dives for squid, fish, crustaceans, and ascidians. The main foraging areas are located in Antarctic waters. Males forage in areas over the Antarctic continental shelf while females tend to search for food in deeper, offshore waters. Most of the time at sea is spent submerged, with records of 1,430 m and 120 minutes (5). They have no natural predators, but will fight each other, vocalising as a threat, and then raising the front half of the body and slamming it into another seal (1).

In the 18th and 19th centuries southern elephant seals were hunted for fur for clothing, and oil for mechanical lubrication, but this no longer occurs, and the population recovered under later protection (1) (5). A large-scale sealing industry was allowed in the 20th century by the government of South Georgia from 1909 to 1964. It was restricted to adult males but caused population decline, which again was reversed under a research-based management plan (5).

The southern elephant seal population is currently estimated at 650,000 individuals (3), but has decreased significantly over the last 40 years. Reasons for this decline are unknown, as other mammals in the southern oceans do not appear to have suffered similar declines. It has been suggested that populations increased rapidly following the drop in commercial sealing, overshooting the maximum population that could be supported by the ecosystem, and are now dropping back to equilibrium (4).

An increase in commercial fishing in this area could cause future problems. Seals are seen entangled in net as well as covered in oil. A research group studying southern elephant seals had been using hot iron branding to mark individuals, but the Tasmanian government banned this activity after it was found that branded seals were more likely to be in poor condition than unbranded seals (4).

Southern elephant seals are protected by the U.S. Fish and Wildlife Service's Marine Mammal Act 1972, but research into the reasons behind the decline of this species must be conducted before management plans can be drawn up (3). Priorities for research need to focus on the continuation of census programmes, demographic studies and investigations into several aspects of the biology of first-year seals, particularly diet and foraging ranges (5). Some populations of southern elephant seals are found in a 16 million hectare protected Marine Park on the eastern side of Macquarie Island (4).

For further information on this species see Sea Map:
http://seamap.env.duke.edu/species/tsn/180671

For more information on this and other seal species see the Seal Conservation Society:
http://www.pinnipeds.org/species/selephnt.htm

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk