(Linnaeus, 1758) - Southern elephant seal
Distinctive Characteristics
Southern elephant seals are the largest pinnipeds. They are massive and impressively built in every respect, exhibiting significant sexual dimorphism in size and secondary sexual characteristics. 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 very blunt on females and young subadult males. The eyes are large, a feature that is particularly noticeable in females and subadults. The mystacial vibrissae are beaded, short, and black, with 1 or 2 nose, or “rhinal” whiskers off to each side of the muzzle, and up to 7 vibrissae above each eye. Each foreflipper digit bears a large blackish brown nail.
Adult males are unmistakable. The proboscis is erectile. 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, a thickened area of heavily scarred and creased skin, which also is not as pronounced as in the northern elephant seal. There are various amounts of scarring on the rest of the body, and the proboscis is often heavily scarred or torn. Adult females, and subadults do not have a proboscis, but rather a short nose and muzzle, which with their very wide head gives them a somewhat “pug” appearance.
Elephant seals have an unspotted pelage of light to dark silver-grey, with no difference between top and underside. Some seals are cream grey to brown late in the year. Many bulls become pale in the face, proboscis, and head with increasing age. Adults and subadults undergo an epidermal moult. Pups are born in a long woolly black lanugo that is shed at about 3 weeks of age, to reveal a silver-grey coat.
The dental formula is I 2/1, C 1/1, PC 5/5.
Can be confused with
The massive head and the large fleshy proboscis make southern elephant seal bulls virtually unmistakable. All 4 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 size and relative proportions of the flippers and head, presence of spotting and streaking (absent on southern elephant seals), and prominence and colour of vibrissae.
Size
Adult males reach 5.8 m and 3000 to 5000 kg, although few have ever been weighed. Adult females are up to 3 m and 400 to 800 kg. Newborn pups are about 1.3 m and 40 to 50 kg.
Geographical Distribution
Southern elephant seals have a nearly circumpolar distribution in the Southern Hemisphere. Although they show up almost anywhere around the Antarctic continent, they are most common north of the seasonally shifting pack ice, especially on subantarctic islands, where most rookeries and haul-outs for moulting are located. Sandy and cobble beaches are prefered, but will haul out on ice, snow, or rocky terraces. They will venture inland into tussock grass and other vegetation, and frequently lie in mud wallows. At sea, females and males may disperse to different feeding grounds.
Biology and Behaviour
Elephant seals are highly polygynous and males compete for access to females by roughly sorting themselves in a hierarchy. There is much fighting, vocalizing, and displaying during the breeding season. One of the male's most impressive displays is achieved by rearing up on his hindquarters, lifting some two-thirds of his bulk, and vocalizing as a challenge to other bulls.
Southern elephant seals are remarkable breath-holders; instrumented adult females have remained underwater for 120 minutes and have reached depths of 1255 m. Both sexes dive nearly continuously while at sea, spending only a small fraction of time at the surface. Prey consists of approximately 75% cephalopods and 25% fish.
Exploitation
Intensive commercial sealing greatly reduced the populations of southern elephant seals and eliminated them from some rookeries, which they have yet to recolonize. The industry was based on the great volume of high quality oil that could be obtained from these seals, especially the bulls. “Elephanting” was in its heyday throughout the 19th Century, with little or no control, and continued until 1964 at South Georgia under a management scheme. Colonies on subantarctic islands in the Indian Ocean area are generally declining for unknown reasons. As with all pinnipeds inhabiting Antarctic regions, southern elephant seals are protected by the Convention for the Conservation of Antarctic Seals.
IUCN Status
Insufficiently known.