Walruses (Odobenus rosmarus)
… are year-round residents of the arctic oceans. Their huge bulk is an adaptation to the cold of the long arctic winter, lowering their surface area-to-volume ratio to keep more heat inside. Males can grow up to 12 feet (3.6 m) long and weigh an average of 2000 lbs (900 kg). They also wear a very thick skin - the skin itself can be up to 4 inches (10 cm) thick on parts of their body, and the blubber layer underneath an additional 6 inches (15 cm).
Their most familiar feature is, of course, their tusks; these can grow up to 3.3 feet (1 m) long. They’re used mainly for dominance and other social displays, and the strongest males with the largest tusks are usually at the head of a group. They may also use their tusks to break holes in the ice and to help pull themselves out of the water, but the long teeth aren’t used in feeding. Walruses eat crustaceans and invertebrates from the sea floor in the shallow areas just offshore.
They find their prey using their faceful of whiskers, called vibrissae. Each is exceptionally sensitive, and with them the walrus can distinguish food items as small as a tenth of an inch (3 mm). Walruses have two other interesting anatomical features: they have an air pouch in their throat that they can inflate to allow them to hang suspended vertically in the water to sleep; and they have the largest baculum (the bone in the penis) of any animal, both relative to body size and in absolute terms, at up to 25 inches (63 cm) long.
photo by Polar Cruises on Flickr
(via: Peterson Field Guides)