Walruses are members of a widely distributed group of marine animals known as pinnipeds (pinna, a wing or fin; and pedis, a foot), a group which also includes the seals and sea lions. Walruses are the largest pinnipeds in arctic and subarctic seas. They are most commonly found in relatively shallow water areas, close to ice or land. Their geographic range completely encircles the Polar Basin. Two forms are presently recognized: the Pacific walrus (Odobenus rosmarus divergens) and the Atlantic walrus (Odobenus rosmarus rosmarus). The principal differences between the two are in the longer tusks and larger body size of the Pacific walrus. The groups may be regarded as closely related but geographically separated subspecies.
Today there are far more Pacific than Atlantic walruses. The 1990 population of the Pacific subspecies was estimated at about 201,000 animals. They are the mainstay of several Eskimo villages. Their flesh is used for food and the skins as boat coverings. The intestines were traditionally used to make rain gear. In the American sector of the Bering and Chukchi seas, walruses occur seasonally from Bristol Bay to Point Barrow. Most of the animals undertake a northward spring migration and return south during the fall. These movements are directly related to the seasonal advance and retreat of the sea ice. About 12,000 to 16,000 bulls remain in the Bristol Bay area from March through October. These males migrate northward in the fall to the St. Lawrence Island area, where they join the rest of the herd to spend the winter and spring in the ice pack.
General description: The genus name for the walrus, Odobenus (meaning tooth-walker), refers to one of their most prominent characteristics, their tusks. These tusks, which are elongated upper canine teeth, are present in both males and females. The body form is basically like a sea lion, and they have flexible hind flippers that can be rotated forward, a thick, heavy neck, and a broad muzzle that bears a heavy, bristly moustache. They are huge animals. Adult bulls often approach 2 tons in weight, and the females may exceed 1 ton. Adult bulls can be recognized by their larger size, broad muzzle, heavy tusks, and the presence of numerous large bumps on the neck and shoulders.
Life history: Walrus calves are born mostly in late April or early May during the spring migration. They weigh 100 to 160 pounds (45-73 kg) at birth. Calves are dependent upon their mothers for at least 18 months and occasionally for as long as 2 1/2 years. Most females do not begin to breed until 6 or 7 years of age. Mating occurs during January and February, but growth of the fetus does not begin until about mid-June. This delay in fetal growth is thought to occur in all pinnipeds. The total gestation period, from conception to birth, is about 15 months. However, the actual period of fetal growth is about 11 months. Most cows do not breed again until the year following the birth of their last calf. Thus, calves are produced in alternate years by females in their prime. Calves are produced less frequently by the older females.
By 2 years of age, the young weigh about 750 pounds (341 kg). When the females are 11 or 12 years old, they weigh approximately 2,000 pounds (909 kg), their maximum weight. The males continue growing until at least 14 to 16 years of age.
The age of an individual walrus (except for very old animals) can be determined by the number of rings or "annual layers" observed in cross-sections of the teeth. In the older animals, some of the rings laid down during the first few years of life are worn away. However, examination of teeth has shown that walruses can reach the age of 40 years. Due to rather constant, significant, and selective hunting pressure, as well as other factors, it is doubtful that very many walruses die of old age.
Food habits: Walruses feed mainly on bottom-dwelling invertebrates found on the relatively shallow and rich Bering-Chukchi Platform. Major food items include several different kinds of clams. Only the fleshy parts are eaten. It is believed that these parts are torn away from the rest of the clam by strong suction, a method of feeding for which the mouth of the walrus is ideally designed. The mouth of a walrus is narrow, with an unusually high roof, strong thick lips which are not deeply cleft along the side of the face (the gape is extremely limited), and a thick piston-like tongue. The tusks are probably not used to any great extent during feeding. The rejected shells can be found on the sea floor alongside the holes and furrows made by feeding animals. Other food items include snails, crabs, shrimps, worms, and occasionally seals. Walruses usually find food by brushing the sea-bottom with their broad, flat muzzles.
Behavior: The tusks are used for fighting, for climbing on both land and ice, and for emergencies of various kinds. A female walrus was observed literally demolishing a heavy piece of ice to free her calf, which had fallen into a crevasse. The tusks were as effective as a pick-axe. The presence of 12 men within 30 feet did not distract her from her task. Attempts to assist her in her efforts were met by furious charges and a threatening noise made by rapidly opening and closing her mouth. The noise sounded much like someone banging a pipe with a hammer. In due time she freed her calf and swam off, carrying it on her back.
Cows will not abandon their calves, and vice versa. The cows make every effort to rescue their offspring. They often carry their dead calves away from the hunters. Walruses, especially young males, will push dead and badly wounded animals (often larger than themselves) off an ice floe, out of the reach of the hunters. They will frequently return to an ice floe for as long as wounded animals continue to bellow. This sometimes places both people and boats in jeopardy. The return is not a reprisal attack but an attempt to lead the wounded animals to safety. A person imitating the sounds of a walrus can frequently get them to return.
Walruses (with the exception of some young bulls) are usually not malicious, but their inquisitiveness, size, and great strength demand caution of those who approach them.
Tusks are used a great deal in mutual display, with the strongest animals (usually with the largest tusks) being dominant over the others. When animals on an ice floe are disturbed, which happens frequently, they will raise their heads high, prominently showing their tusks. Animals with smaller tusks will usually move away or become respectfully quiet. The only serious battles (and these are quite brutal) are between animals of the same body and tusk size.
Hunting: Walrus hunting is conducted from all of the Eskimo villages near which the animals occur. However, the bulk of the annual harvest is taken from the villages in and near Bering Strait, mainly Gambell, Savoonga, Nome/King Island, and Little Diomede Island. Hunting loss can be high. Several thousand animals are killed annually in Alaska. Some walruses are also taken by Siberian Eskimos and by Russian commercial hunting vessels.
The most favorable period for hunting walrus is during the spring and summer when the animals are passing the villages on their way north. Hunting is good on St. Lawrence Island during May, and progressively later at the most northerly locations. Walruses reach the vicinity of Wainwright and Barrow during late July or early August.
Text: John J. Burns
Illustration: Alaska Fisheries Science Center, Sandra Noel
Revised and reprinted 1994
