Southern elephant seal - Mirounga leonina

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The southern elephant seal is the largest pinniped species. In both sexes, the body is robust and the neck is very thick. The head, muzzle, and lower jaw are broad. The mystacial area and nose are fleshy and blunt, and the bridge of the nose angles down slightly to the nostrils on females and young subadult males. The eyes are large, widely-spaced, and have a forward orientation that is especially noticeable in females and subadult males. The vibrissae are beaded, short to medium length, and black. In addition to the mystacial clusters, there are one to two vibrissae on the bridge of the nose, and several in prominent supra-orbital patches above and slightly behind each eye. Each fore flipper digit bears a large blackish-brown nail. The nails on the hind flippers rarely emerge, but there is a vestigal nail beneath a small opening located above the end of each hind flipper digit.

Adult males are unmistakable. The long and enlarged nose, the proboscis, is inflatable. When relaxed, it hangs down in front of the mouth. Curiously, the proboscis is shorter in the southern than in the northern elephant seal, even though the former has a larger body. The proboscis is said to enlarge somewhat during the breeding season. Bulls also develop a chest shield of thickened, creased and heavily scarred skin. The chest shield on southern elephant seals is also not as developed as those on northern elephant seals. There is a varying amount of scarring on the rest of the body, and the proboscis is often heavily scarred or torn. Many bulls become pale in the face, proboscis, and head with increasing age. In addition to their much longer and larger body size, males also have larger canines that are both considerably longer and thicker than those of adult females.

Adult southern elephant seals have an unspotted pelage of light to dark silver gray, or tan to dark brown with little to no difference between dorsal and ventral coloration. Their coloration fades as time progresses from the end of the last annual molt. Southern elephant seals also become stained rusty orange and brown, from lying in their own excrement when ashore on beaches and in muddy wallows and tussock grass areas. During the annual epidermal molt they look ragged as they slough patches of faded and soiled fur with skin attached to reveal the new, clean, dark silver gray fur coming in underneath. The molt begins in the axillary region, between the hind flippers around the tail, and around scars. Pups are born in a long woolly black lanugo coat that is shed at about 3 weeks of age, to reveal a silver gray countershaded coat that is yellowish gray ventrally.

Adult males typically reach 4.5 m and a maximum of 5.8 m in length weigh 1,500-3,000 kg with a maximum weight of about 3,700 kg. The literature contains numerous accounts of much larger males, with maximum lengths of 6-7 m, but these dimensions usually include hind flippers, whereas the standard length in use today is from tip of nose to tip of tail. Adult females are similar in size and weight to northern elephant seal females weighing 350-600 kg with exceptionally large females reaching 800 kg. Newborn pups are about 1.3 m and 40-50 kg.

The dental formula is I 2/1, C1/1, PC 5/5.

The massive head and the large fleshy proboscis make southern elephant seal bulls virtually unmistakable. All four other phocids that occur within the southern elephant seal's range: Weddell, Ross, crabeater, and leopard seals can be separated from any age southern elephant seal by coloration and the presence of many to few spots, areas of spotting, blotches of color, or stripes. With the exception of crabeater seals, all three other species are noticeably countershaded as adults, whereas southern elephant seals have slight to no countershading as subadults and adults. The head of female and subadult elephant seals is proportionately large and broad and the muzzle is broad, massive and somewhat blunt, with more forward facing nostrils. The vibrissae of elephant seals are black, relatively long and conspicuous, whereas they are noticeably inconspicuous and pale in the other species.

Southern elephant seals have a nearly circumpolar distribution in the Southern Hemisphere. Although they reach the Antarctic continent, and even very high latitude locations such as Ross Island, they are most common north of the seasonally shifting pack ice, especially in Subantarctic waters where most rookeries and haul-outs are located. Notable exceptions include the northern breeding colonies at Peninsula Valdez in Argentina, and on the Falkland Islands. Also, some pups are born on the Antarctic continent. Southern elephant seals prefer sandy and cobble beaches, but will haul-out on sea ice, snow, and rocky terraces, and regularly rest above the beach in tussock grass and other vegetation, and in mud wallows. At sea, females and males may disperse to different feeding grounds. Wandering and vagrant southern elephant seals reach southern Africa, southern Australia, New Zealand and Brazil in South America. An Indian Ocean record at Oman on the Arabian Peninsula represents northernmost record.

Southern elephant seals spend a large percentage of their lives at sea far from land, and only return to land to give birth, breed, and molt. At sea, they range far from their rookeries and predominantly feed between the Subantarctic convergence and the northern edge of the pack ice, south of the Antarctic convergence. Adult males typically venture further south than females, and are known to forage at the seaward edge of the Antarctic continental shelf.

They are prodigious divers and routinely reach the same depths as their northern counterparts. Dive depth and duration vary during the year and between the sexes, but normally range from 300 to 500 m deep and from 20 to just over 30 minutes in duration. A maximum depth of 1430 m was recorded for a female, following her return to sea after the molt. Another post-molt female dove for an astonishing 120 minutes, which is by far the longest dive ever recorded for a pinniped.

Southern elephant seals are highly polygynous with males establishing dominance hierarchies on beaches to monopolize access to groups or harems of females. Adult males return first in August, and most of them are ashore by mid-September to establish their status in the breeding hierarchy through displays, vocalizing and violent fighting. One of the male's most impressive displays is achieved by rearing up on his hindquarters and lifting almost two-thirds of his bulk straight up to fight with a peer or issue vocal challenges to nearby bulls.

Pregnant females arrive from September to October, and usually give birth within five days of their return. Pups are nursed for an average of 23 days, and abruptly weaned when the female departs to sea. Females come into estrous about four days before they wean their pup and mate, starting a new reproductive cycle before completing their current effort. Females first return to mate somewhere between three and six years. Pups remain on the breeding beaches for eight to ten weeks, during which time they complete the molt of their lanugo coat, before departing to sea.

Vocalizations include a booming, loud call of the adult male in the breeding season, variously called a bubbling roar, a harsh rattling sound, and a low pitched series of pulses with little variation in frequency. Adult females have a high-pitched yodeling call which they use when distressed, and to call their pups. They will also utter a low pitch, sputtering growl. Pups call to their mothers with a sharp bark or yap, which is also used when interacting with other seals.

Relatively little is known of southern elephant seal prey, although much has been learned of their foraging grounds and diving activities. It has been reported that prey consists of approximately 75% squid and 25% fish. Antarctic Notothenia fishes are thought to be important prey when these seals are near the Antarctic continental shelf. Most feeding by females occurs in deep ocean areas at mid-water depths. Adult males pass through female feeding areas on their way south to Antarctic continental slope and shelf waters, where their diving activity suggests they pursue more benthic prey.

The worldwide population of southern elephant seals is currently estimated at 650,000. Colonies in the South Atlantic, which include the largest breeding aggregation at South Georgia, are stable or growing, while those in the Southern Indian and Pacific Oceans have decreased by up to 50%. The reasons for these declines, which began in the 1950s and 1960s and are ongoing at the present, are not understood.

Southern elephant seals were hunted for thousands of years by aboriginal and native peoples in Australia and South America. More recently, they were subjected to intensive commercial harvests starting in the early 19th century and not ending until 1964 at South Georgia. They were prized for their large quantity of blubber that could be rendered to fine, valuable oil.

There are few threats and conflicts today, as southern elephant seals live far from human population centers and have minimal interactions with commercial fisheries. Intensive fishing could potentially deplete important prey stocks. However, little is known of feeding habits and much work needs to be done to develop management plans that would be effective.

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Campagna, C., M.A. Fedak and B.J. McConell. 1999. Post-breeding distribution and diving behavior of adult male southern elephant seals from Patagonia. Journal of Mammalogy 80(4):1341-1352.

Hindell, M.A. and H.R. Burton. 1988. Seasonal haul-out patterns of the southern elephant seal (Mirounga leonina L), at Macquarie Island. Journal of Mammalogy 69(1):81-88.

Hindell, M.A., H.A. Burton and D.J. Slip. 1991. Foraging areas of southern elephant seals, Mirounga leonina, as inferred from water temperature data. Australian Journal of Marine and Freshwater Research 42:115-128.

Hindell, M.A. 2002. Elephant seals Mirounga angustirostris and M. leonina. pp. 370-373 in W.F. Perrin, B. Würsig and J.G.M. Thiewissen, eds. Encyclopedia of marine mammals. Academic Press.

Laws, R.M. 1994. History and present status of southern elephant seal populations. p 49-65 in B.J. Le Bouef and R.M. Laws (eds.), Elephant seals. University of California Press.

Ling, J.K. and M.M. Bryden. 1981. Southern elephant seal-Mirounga leonina Linnaeus, 1758. pp. 297-327 in S.H. Ridgway and R. Harrison (eds.), Handbook of marine mammals, Vol. 2: Seals. Academic Press.

Slip, D.J., M.A. Hindell and H.R. Burton. 1994. Diving behavior of southern elephant seals from Macquarie Island: An overview. pp 253-270 in B.J. Le Bouef and R.M. Laws (eds.), Elephant seals, University of California Press.