Southern elephant seal (Mirounga leonina)
|French:||Eléphant De Mer Du Sud, Eléphant De Mer Méridional|
|Spanish:||Elefante Marino Del Sur|
|Size||Male weight: up to 3700 kg (2)|
Female weight: 400 - 900 kg (2)
Classified as Least Concern (LC) on the IUCN Red List (1), and listed on Appendix II of CITES (3).
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 and females become paler across the face, proboscis and head as they age (4). During the annual moult, southern elephant seals become stained rusty orange and brown from lying in their own excrement (6).
The global southern elephant seal population is thought to be separated into three, possibly four breeding “stocks”. These are further divided across separate archipelagos or islands. During the minor portion of their lives that they haul out for breeding, moulting or resting they come ashore on isolated islands of the Southern Ocean. One small population hauls out at a single location on the South American coast, and some animals regularly haul out on the Antarctic Coast, but the largest populations are found at the island of South Georgia, near the southern-most tip of South America; Macquarie Island, 1,500 kilometres south-southeast of Tasmania; and Kerguelen Island, midway between Africa, Antarctica and Australia. While at sea, southern elephant seals move to locations that may be several thousand kilometres distant from their haulout sites (6).
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).
Spending the vast majority of their lives far our at sea, southern Elephant seals haulout on land at regular intervals. As immatures they alternate between a spring or summer moult haulout and a winter haulout of unknown purpose. As adults they alternate between a spring breeding haulout and a summer or autumn moult haulout. They do not feed while on land, but rely on their blubber for energy (2) (6).
Breeding takes place from late August to late November each year. At this time adult 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, when the females collect together into groups known as ‘harems’. Access to females within a group is dominated by a single male, known as a ‘beachmaster’, but in very large harems, one or more sub-dominant males may gain access to females. Competition amongst males is intense, with fighting, vocalizing and impressive displays taking place. 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 male. Once the pup is weaned, the females return to the sea leaving the pups to fend for themselves. The pups remain ashore or in the shallows for four to six weeks before leaving the beaches for the ocean (2) (6).
Between November 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 (2).
Southern elephant seals are remarkable divers, with dives deeper than 2,133 metres and as long as 120 minutes recorded (7) (8). They spend 70 to 80 percent of their lives below the sea surface (8). Southern elephant seals are thought to feed primarily on squid, but also fish, crustaceans, and ascidians. At sea they are found between the Subantarctic Front and the pack ice, with males moving further south than females (1).
In the 18th and 19th centuries southern elephant seals were hunted extensively for their oil which was used for mechanical lubrication (2) (7), which resulted in many populations declining. A carefully managed sealing operation continued at South Georgia until 1964, but populations have recovered since the cessation of most sealing activities (4) (7). Between 1960 and 2000 numbers of the southern elephant seal declined in a number of smaller populations. The reasons for this decline are unclear, but it is thought to be due to changes in distribution and abundance of the seal’s prey; however, it appears that this decline has ceased (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 (7). Most breeding sites of the southern elephant seal are subject to some form of protection, such as at Peninsula Valdés, Argentina (9), and MacQuarie Island Nature Reserve and World Heritage Site (10).
For more information on the conservation of the southern elephant seal and other seal species, see:
Seal Conservation Society:
Authenticated (09/09/2010) by Greg Hofmeyr, Marine Mammal Biologist and Curator, Bayworld (Port Elizabeth Museum, Oceanarium and Snakepark), Port Elizabeth, South Africa.
- Ascidiacea: a class of sea-squirts; members of the subphylum Urochordata.
- Crustacea: diverse group of arthropods (a phylum of animals with jointed limbs and a hard chitinous exoskeleton) characterised by the possession of two pairs of antennae, one pair of mandibles (parts of the mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, slaters, woodlice and barnacles.
- Proboscis: a tubular protrusion from the anterior of an animal (e.g. the trunk of an elephant).
- Sexually dimorphic: males and females of the same species differ in appearance.
IUCN Red List (September, 2010)
- Hindell, M.A. (2002) Elephant Seals. In: Perrin, W.F., Würsig, B. and Thewissen, J.G.M. (Eds.) Encyclopedia of Marine Mammals. Academic Press, London, UK.
CITES (September, 2010)
- Jefferson, T.A., Leatherwood, S. and Webber, M.A. (1993) FAO Species Identification Guide. Marine Mammals of the World. Food and Agriculture Organization of the United Nations, Rome.
- Macdonald, D.W. (2006) The Encyclopedia of Mammals. Oxford University Press, Oxford.
- Hofmeyr, G.F.G. (2010) Pers. comm.
- Le Boeuf, B.J. and Laws, R.M. (1994) Elephant seals: population ecology, behaviour and physiology. University of California Press, Berkeley, California.
- McIntyre, T., de Bruyn, P.J.N., Ansorge, I.J., Bester, M.N., Bornemann, H., Plötz, J, and Toch, C.A. (2010) A lifetime at depth: vertical distribution of southern elephant seals in the water column. Polar Biology, 33: 1037-1048.
- Reeves, R.R. (2002) Conservation Efforts. In: Perrin, W.F., Würsig, B. and Thewissen, J.G.M. (Eds.) Encyclopedia of Marine Mammals. Academic Press, London, UK.
UNEP-WCMC (September, 2010)