The walrus is a member of the pinniped family, which also includes sea lions and seals. Walrus differ from some seals in that they can turn their hind limbs forward. This characteristic enables them to raise themselves up, giving them greater freedom of movement on land. Two subspecies, the Atlantic and Pacific walrus, live in the arctic and subarctic regions of the Northern Hemisphere. The Pacific walrus is the largest.
The walrus is covered by a thick layer of fat and a tough leathery skin with a thin layer of hair which is light brown on adults and almost black on young walrus. The walrus' head is small in comparison with its heavy, clumsy body, and the upper lip is thick and fleshy with a stiff moustache made up of bristles which are important sensory organs. Although there are other teeth in the upper jaw, it is the greatly enlarged canine teeth, called tusks, that give the walrus its distinctive appearance. Both the male (called a bull) and the female (called a cow) have tusks; however, those of the male are much larger. Males may weigh over a ton and reach a length of more than 10 feet. Females are about a third smaller with a maximum length of about 9 feet.
In the summer, bulls live together in bachelor groups, but during the midwinter mating season (January through March) walrus congregate in groups called mobile leks in regions of ice-free water. Bulls may fight viciously over cows, and the victorious bull always keeps an eye out for other males who would steal his females if given the opportunity.
Females give birth to a calf every 2 to 3 years. The young are born out on the ice in April or May. At times when a calf is not sleeping or nursing, the mother allows it to crawl over her or she may play with it, holding it between her front flippers and lifting it into the air. A calf may nurse for up to 2 years.
The adults may take a swim to feed, but the young are never left completely alone. While both sexes watch for enemies such as polar bears, the females are solely responsible for the protection of their offspring. If a walrus group, or lek, is disturbed and leaves the ice floe, the adults stay close to their young to protect them.
Walrus primarily eat species that dwell on the sea bottom, such as mollusks; salt worms; crabs, shrimp, and other crustaceans; and octopus. The walrus drags its tusks like sled runners along the sea bottom, rooting out buried prey with its snout and stiff facial bristles. Occasionally walrus may consume other pinnipeds such as spotted, ringed, and bearded seals.
Tusks also serve as an indicator of social rank and may be used as protection. Sometimes, when a walrus wants to rest while still in the water, it will hook its tusks over the edge of an ice floe. Tusks may also be used to break up an ice floe to keep breathing holes open or to retrieve calves that have become stuck in the ice.
Walrus spend most of their lives at sea, although they frequently come out of the water, or haul out, onto ice floes or land to rest. They also leave the water to give birth to their young and to shed their hair. Keeping mainly to the moving ice packs, walrus migrate north in spring and south in winter.
For thousands of years, the walrus was regarded by Eskimos and other Native people of the North as having supernatural powers and human attributes. It was also a natural resource of major importance to their culture. They obtained food and fuel from the walrus, as well as raw materials for making tools, shelter, boats, sleds, and clothing. The walrus was hunted for centuries by Russians, Americans, and others for its valuable ivory tusks and oil.
In the United States, the walrus became a federally protected species with the passage of the 1972 Marine Mammal Protection Act. This Act established a moratorium on the taking and importation of various marine mammals, their parts, and products. However, the Act allows Eskimos and other Alaskan Natives to take walrus for subsistence, and their parts for use in certain handicraft articles.
The monitoring of the walrus population through periodic surveys is one effort the U.S. Fish and Wildlife Service undertakes to fulfill its responsibilities under the Act. The last survey was done in 1990 in cooperation with Soviet biologists, and at this time, the walrus population appears stable, with more than 200,000 individuals.
Among the threats facing the walrus today are habitat alteration, illegal hunting, human activities on or near hauling- out grounds, and disturbance by commercial fishing and oil and gas exploration and extraction.