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(Lesson, 1826) - Weddell seal

Distinctive Characteristics

Female Weddell seals tend to be slightly larger and heavier than males, but not enough to distinguish the sexes. Much of the year the body is sufficiently plump that the head appears disproportionately small. However, extensive weight loss during the spring breeding season makes the size of the head less useful. There is no discernable demarcation of the forehead. Several features contribute to a cat-like appearance: the very short and blunt muzzle, large and fairly close-set eyes, a sparse number of inconspicuous short vibrissae, and a mouthline that is turned up at the corners. The foreflippers are more pointed and angular than those of northern phocids, and are proportionately the shortest of any antarctic phocid.

Adults are generally dark silver-grey above and off-white below, with variable spotting, streaking, and blotching. These markings are lighter on the back, heavier on the sides, and sometimes continuous on the undersides. Dorsal colour progresses from bluish black just after moulting to brownish grey just prior. The muzzle, from the nostrils to the mouth and mystacial area, is usually pale, as are crescent-shaped markings over the eyes. Pups are born in a woolly silver-grey coat, with a darker swath along the midline of the back. They shed the lanugo for the adult pelage in 1 to 4 weeks.

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

Can be confused with

Of the 4 phocids that share the Weddell seal's range, Ross and crabeater seals are the most similar (leopard and southern elephant seals are easy to distinguish). Note the proportionately larger and wider neck and head, and stripes of the Ross seal; and for the other species, characteristics of the muzzle, head, neck, colour pattern, flippers, and vibrissae.

Size

Adult males reach 2.9 m in length, females 3.3 m. Adults in their prime weigh 400 to 450 kg, with a wide seasonal fluctuation. Newborns are 1.5 m long and average 29 kg.

Geographical Distribution

Circumpolar and widespread in the Southern Hemisphere, Weddell seals occur in large numbers on fast ice, right up to the Antarctic continent, and offshore through the pack ice to the seasonally shifting limits of the Antarctic Convergence, including many seasonally ice-free islands along the Antarctic Peninsula.

Biology and Behaviour

Weddell sealsbreed from September through November, depending on the locality; those in lower latitudes pup earlier. Males set up territories in the water around access holes in the ice used by females.

Weddell seals are not very social when out of the water, avoiding physical contact most of the time. The only copulation that has been observed occurred underwater. They may congregate in groups on fast ice near access holes to the water. If disturbed when out of the water Weddell seals often roll onto a side and arch their neck and chest, raising the head to look around. There is some debate over whether or not this species is migratory. Some individuals remain in residence year round in the fast ice. Others, particularly newly weaned and subadult animals, move north from the continent into the winter pack ice.

Weddell seals can dive very deeply (to 700 m), and to hold their breath for up to 82 minutes. The deep diving abilities are helpful in finding breathing holes and obtaining important prey such as the huge Antarctic cod. The diet of Weddell seals consists mostly of fish, with smaller amounts of squid and other invertebrates rounding out their fare.

Exploitation

Weddell seals have never been exploited by full-scale commercial sealing. Throughout the Antarctic they have been relied upon by early explorers and scientific programmes as a food source for people, and more recently for sled dogs. Small numbers are regularly taken for research purposes. These and all other Antarctic seals are protected by the Convention on Conservation of Antarctic Seals.

IUCN Status

Insufficiently known.

Weddell seal (Leptonychotes weddellii)