Image:Walrus.jpg

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Walrus, large marine mammal related to seals, notable for a pair of long ivory tusks formed by the canine teeth in the upper jaws. The walrus is found only in Arctic regions in the Northern Hemisphere. It is the second largest pinniped (member of the Pinnipedia suborder of carnivores) after the elephant seal. The name walrus comes from a Dutch word meaning “whale-horse.”

II Habitat and Range

Print this section Walruses live in the Arctic regions at the edge of the polar ice. There are two main populations, the Atlantic walrus and Pacific walrus. They are often classified as distinct subspecies.

The Atlantic walrus is found in the northern Atlantic Ocean and Arctic Ocean along the northeastern coasts of Canada, along coasts of Greenland, around northern Norway, including Svalbard Island, and around the Novaya Zemlya peninsula in northern Russia.

The Pacific walrus is found in the North Pacific Ocean around the Bering Sea and in the Arctic Ocean, mainly along the northeastern coasts of Siberia and the northwestern coasts of Alaska. A separate population of Pacific walrus sometimes considered a third subspecies is found around the Laptev Sea off northern Siberia.

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Most walrus populations migrate southward in the winter and northward in the spring. Walruses commonly use pack ice for resting, molting, and bearing young, but they also come ashore on land.

III Description and Behavior

Print this section Walruses range from 2.7 to 3.56 m (8.9 to 11.7 ft) in length and weigh 800 to 1,700 kg (1,800 to 3,700 lb); males are larger than females. The Pacific walrus is somewhat larger than the Atlantic walrus, and has a wider skull and longer tusks. Walruses have relatively small heads with no external ears; a fold of skin marks the location of the ear. Walruses also have broad muzzles, with large, sensitive whiskers used in finding food. Both the male and female walrus have massive bodies with thick, wrinkled, hairy skin that becomes nearly hairless with age.

The skin color of the walrus is generally a cinnamon-brown. However, the skin contains tiny blood vessels that can be constricted in cold water to conserve body heat, making the walrus appear almost white. On land or in warm conditions, the blood vessels can be expanded to shed heat, making the walrus’s skin appear pink. A thick layer of blubber lies under the skin, helping insulate the walrus against cold. The walrus can also convert the stored fat in its blubber into an energy source when food is scarce. Walruses molt their coats of hair every year.

Both the front and hind limbs have flippers, with the digits covered in a fleshy pad. The hind limbs are used for propulsion in water, with the front limbs used mainly for steering, and sometimes paddling. Walruses can swim at up to 35 km/h (22 mph). Like eared seals, walruses can turn their hind limbs forward and thus use all four limbs in moving when ashore.

The enormously elongated upper canine teeth form heavy tusks that can be up to 1 m (about 3 ft) long in some males. The animal’s genus name, Odobenus, means “tooth-walker” in reference to the tusks. The tusks were once thought to rake the ocean bottom for shellfish, but there is no evidence for such behavior. Instead, the tusks are used as weapons in fighting or for defense, and as hooks in climbing on the ice.

Walruses are highly social animals, congregating in herds—sometimes numbering several thousand animals—on or near the shore or among the ice floes. Walruses make a wide variety of vocal sounds and the bellowing of a herd can be heard for great distances. Walruses are gentle unless attacked; the whole herd will come to the defense of a member in danger. Males and females form separate herds except during mating season. The normal life span in the wild is from 16 to 30 years, with a maximum of over 40 years.

IV Diet and Feeding

Print this section Mollusks and other shellfish foraged from the ocean floor make up the principal food of the walrus. The animal’s sensitive whiskers and fleshy snout play an important role in detecting prey. Research shows that the walrus has a special technique to feed on burrowing shellfish and other invertebrates. It uses its tongue and mouth cavity to squirt a powerful jet of seawater into the sea floor, clearing sand from around its prey, which it then sucks up into its mouth. Adult walruses may eat up to 6,000 clams at a single feeding. Walruses also feed on crabs, snails, and sea cucumbers. They sometimes catch fish and, more rarely, eat dead seals.

The main natural predators on the walrus are the polar bear and the killer whale. Polar bears sometimes prey on young walruses. Killer whales may attack walrus calves or injured adult walruses at sea.

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