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Walruses are large tusked pinnipeds (related to seals) that live in the far north, on the boundaries of the Arctic Ocean. The only living members of the Odobenidae family and Odobenus genus, the scientific species name for walruses is O. rosmarus. There are three geographically isolated subspecies, the Atlantic Walrus (O. rosmarus rosmarus), living in the Atlantic Ocean, the Pacific Walrus (O. rosmarus divergens), living in the Pacific Ocean, and the Laptev Walrus (O. rosmarus laptevi), living in the Laptev Sea just north of Siberia. These subspecies are thought to have split between 500,000 and 785,000 years ago.
The walrus is a memorable animal, with huge white tusks, immense bulk, and whiskers (vibrissa) to help it from bumping its head against the bottom of the sea when it forages for food. Male walruses can weigh up to 4,400 lb (1,996 kg), but typically average around 2000 lbs (889 kg), and measure 11-11½ ft (3.3-3.45 m) in length on average. The tusks alone can measure 3.2 ft (1 m) in length. The females are about two-thirds the size of males, and the Pacific subspecies is about 10% larger than the Atlantic subspecies.
There are about 200,000 Pacific walruses, 20,000 Atlantic walruses, and 10,000 Laptev walruses. They gather in huge colonies, sometimes numbering tens of thousands of individuals. Walruses are opportunistic feeders, foraging on the sea bottom for tube worms, soft corals, shrimps, crabs, tunicates, and sea cucumbers. Their favorite food are benthic bivalve mollusks, which they extract from their shells using tremendous suction power, the distinctive feature of their biological family.
The tusks of walruses are used for a variety of purposes: fighting, dominance displays, poking holes into the ice, and hauling itself out of the water and onto the ice. It used to be thought that the tusks were used to stir up the ocean floor and find food, but closer studies have revealed that the front end of the snout is actually used for this purpose. Walrus tusks have historically had great value in the ivory trade, prompting the poaching and exploitation of this species. In recent times, however, this hunting has been tightly regulated, and two subspecies of walruses are rated as "least-concern" by the International Union for Conservation of Nature and Natural Resources, with the third subspecies listed as "data deficient".
Walruses have only two natural predators — polar bears and the orca. However, they are not a prominent part of either's diet, and killing an aggressive walrus can be a huge hassle for either species.