Walrus: Odobenidae

The walrus is the second largest pinniped, after the elephant seal. Walruses are 44 to 126 inches (112 to 320 centimeters) long and weigh 139 to 2,662 pounds (63 to 1,210 kilograms). Their streamlined, smooth, body allows for easy movement through water. They are sparsely covered with short, cinnamon brown hair, which is darker in young walruses. In older males, the hair is almost absent, giving a naked appearance. The wrinkled skin measures 0.75 to 2 inches (2 to 5 centimeters) thick. Adult males have large, coarse bumps on the neck and shoulders. Underneath the skin is a layer of blubber, or fat, about 0.4 to 6 inches (1 to 15 centimeters) thick, which protects against the cold and serves as storage for food energy.

Although its head is quite small compared to the rest of its body, the walrus has a powerful skull. If the seawater freezes while the walrus is underwater, it uses its skull like a sledge-hammer to break through the ice overhead, up to 8 inches (20 centimeters) in thickness. The walrus has no external ears, just small openings covered by a fold of skin. About 600 to 700 stiff whiskers form a mustache and act as antennas for detecting prey. The thickened upper lip is used to feel around for food in the muddy sediments of the ocean floor. Two air pouches in the throat extend to the shoulders. They can be inflated to function as life preservers, enabling the walrus to sleep or rest in an upright position with its head above water. Males produce bell-like sounds with these inflated air pouches when courting females.

Walruses have webbed flippers. The back flippers act as paddles for swimming, while the front flippers do the steering. On land or ice, walruses use their flippers the same way eared seals use theirs. The back flippers are turned forward and, together with the front flippers, are used for moving around. However, unlike eared seals, walruses cannot lift their enormous body off the ground. They walk by pushing off the ground with the help of the belly and flippers. The thick blubber helps cushion its underparts while walking.

The walrus is known for its long, ivory tusks, which are enlarged upper canine, dagger-like, teeth. The teeth first extend out of the mouth when they are about one year old. The tusks serve many functions. They are used for hauling out (getting out of the water) onto the ice. This is where the first part of the walrus's scientific name came from. The Greek word odobenus means "tooth walker" or "one who walks on his teeth." The tusks are also used to threaten rivals for breeding territories and for actual fights. Dominant males typically have larger tusks and use them as power displays. Walruses sometimes use their tusks to support their head while sleeping or resting on ice. They sleep or rest vertically in water with the tusks hooked over the edge of an ice floe, a large sheet of floating ice. The tusks grow with age. In adult males, they can grow up to 3 feet (1 meter) long and weigh about 12 pounds (nearly 5.5 kilograms) each.