Southern elephant seal  (Mirounga leonina)

Instantly recognisable by the large, inflatable proboscis, the male southern elephant seal is the biggest seal in its family. Males can weigh eight to ten times as much as females, making them the most sexually dimorphic of all mammals (2). Females do not have a proboscis, but rather a short nose and a muzzle (4). Both sexes have robust bodies, thick necks and broad heads, and each digit of the fore flippers bears a large, black nail (4). The coat is light to dark silvery-grey or brown in adults and juveniles, whilst newborns have black coats, which turns into a short silvery-grey coat at around three weeks of age (5). Males develop a chest shield of thickened, creased and heavily scarred skin as they age, and also become paler across the face, proboscis and head (4). During the breeding season, southern elephant seals become stained rusty orange and brown from lying in their own excrement.

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-southeast of Tasmania; and Kerguelen Island, midway between Africa, Antarctica and Australia (5).

Inhabits the open ocean during the non-breeding season, where they can dive to remarkable depths (2). During the breeding season, the southern elephant seal is generally found on beaches and rocky terrain, and sometimes on ice and snow (4).

In August 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. Competition for this alpha position is intense, and results in much fighting, vocalizing and impressive displays. The females give birth to a single pup, two to five days after arriving on the breeding grounds. The pups are nursed for around 23 days, but several days before weaning their pups, the females are mated by the dominant males. Once the pup is weaned, the females return to the sea leaving the pups to fend for themselves, and they teach themselves to swim and hunt for four to six weeks before leaving the beaches for the ocean (2).

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. As much as 90 percent of their time at sea is spent submerged (2), and thus have an incredible ability to dive to depths as great as 1,430 meters for as longs as 120 minutes (6). Between January and April, the southern elephant seal will again haul itself out onto beaches to molt (5). Molting, during which these enormous mammals gain new skin and hair, can take three to five weeks, during which time the seal relies in stored blubber to provide energy (2)

In the 18th and 19th centuries southern elephant seals were hunted extensively for their fur for clothing, and oil for mechanical lubrication (2) (6), and a large-scale sealing industry continued in South Georgia until 1964 under a management scheme (4) (6). This exploitation resulted in many populations declining, which recovered after the cessation of such activities (6), however, since the 1950s and 1960s, numbers of the southern elephant seal have again decreased significantly (2). Reasons for this decline are unclear, but it is thought to be due to changes in distribution and abundance of the seal's prey (2). There is some concern that large-scale fisheries may be competing with the elephant seals for their preferred prey (2).

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. 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 (6). Some of the breeding sites of the southern elephant seal are protected, such as the Provincial Wildlife Reserve of North Point, at Peninsula Valdés, Argentina (7), and MacQuarie Island Nature Reserve and World Heritage Site (8).

For more information on the conservation of the southern elephant seal and other seal species see:

• Seal Conservation Society:
  www.pinnipeds.org

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