The walrus is closely related to the seal but forms its own family, the Odobenidae. Walruses lack external ears and have long tusks, a thick, wrinkled, nearly hairless skin except for long bristles on the cheek pads, and rotatable hind flippers that facilitate locomotion over ice. They grow to enormous size: males may be 12 ft (3.7 m) long and weigh up to about 3,000 lbs (1,400 kg). Females are only slightly smaller. Walruses use their tusks to climb out of the water onto the ice, to stir up clams and other bottom shellfish, and in aggressive encounters.
Most walruses live in herds, and in the late winter and spring they drift along on large floating ice fields. Female walruses have one calf every other year, in April or early May, and the calf may stay with the mother for two years. Walruses may live for up to 40 years. They have long been a source of food, ivory, blubber-oil fuel, and hides to Eskimos. In recent history walrus populations have been devastated by overhunting for their tusk ivory.