Although it is related to seals and sea lions the Walrus is the last living species in its family, and as such its behaviour, anatomy and ecology differs considerably from that of its closest relatives. Among the most prominent traits that set it apart are its enormous canine teeth (referred to as tusks), which protrude from the upper jaws of all adults of this species (although the tusks of females are notably shorter and thinner than those of males.) A Walrus’s tusks serve a variety of functions: they aid a Walrus in dragging itself out of the water, can break through ice to keep breathing holes used to surface for air open, serve as a visual indicator of an individual’s strength (with the highest ranking individuals in a group of Walruses, known as a herd, often being those with the largest tusks), and can be used in combat, both to fight off this species’ few predators (primarily Polar Bears and Orcas) and to battle with rivals to establish social hierarchies and to compete for mates. However, despite being teeth, the tusks are not used when eating (with Walruses feeding by creating suction with their tongue and lips, and having very few teeth besides their tusks.) Found in coastal regions throughout the arctic circle, Walruses spend much of their time foraging for food in shallow waters (typically doing so by rooting through sediment on the seafloor with their snouts and detecting prey using a “moustache” of touch-sensitive whiskers on the upper lip) and prey primarily on marine invertebrates such as clams, shrimps, crabs, worms, snails, octopuses and sea cucumbers (although they may also take small fish, carrion and, on very rare occasions, young seals.) When not feeding, Walruses haul themselves onto sea ice or beaches and gather in large social groups (herds) which may contain hundreds of individuals, typically all of the same sex. During the mating season (which lasts from late December until March) these single-sex herds come together, with males claiming an area of land as their territory before attempting to court females by swimming near their territories and producing a series of booms, whistles and clatters using an air-filled sac in their throat. If receptive to mating a harem of females may gather to mate with a single male, while males that would otherwise show no aggression to one another will use their tusks to fight off rivals in a manner comparable to the rutting behaviour seen in deer. After a gestation period of 15-16 months females will give birth while resting on sea ice (typically to a single calf, although twins have occasionally been reported), and calves will typically remain with their mothers until they are around 3 years old, beginning to develop their tusks during their first year of life. All Walruses belong to one of two genetically distinct subspecies: the Atlantic Walrus (Odobenus rosmarus rosmarus), which is native to the northern Atlantic ocean, and the Pacific Walrus (Odobenus rosmarus divergens), which is native to the northern Pacific ocean.
