The Atlantic walrus (Odobenus rosmarus rosmarus) is the smaller of the two subspecies of Odobenidae, with shorter tusks as well. They usually live in coastal areas of North-eastern Canada and Greenland. On average, a male Atlantic walrus weighs around 1600 pounds, and attains a length of up to 13 feet. Almost of all this weight and size is blubber, which insulates the walrus from the frigid water it lives in. The skin is about 1.5 inches thick, and the blubber is 4 inches thick.

A walruses colour is determined by the temperature of the surrounding air or water. When a walrus is in cold water, blood vessels near its skin surface contract, leaving it a whitish colour. The blood vessels near the internal organs are then expanded, trapping heat in the vital areas. On the other hand, when a walrus is in the sun, blood vessels near the skin are expanded, dumping excess heat and changing the walrus to a red colour. This adaptation is characteristic of both Atlantic and Pacific walruses.

Atlantic walruses, like Pacifics, feed primarily on clams and other bottom-dwelling invertebrates. It was originally thought that a walrus used its tusks to feed at the ocean floor. Recent studies and advancing technology have proved otherwise. The vibrissae (moustache) are attached to sensitive muscles and nerves, so the walrus can feel anything at the ocean floor with its face. Clams have been proven to make up almost 95% of a walruses diet. However, older males have been documented killing and eating seals, and (God knows how) even sea birds.

The main predators of Atlantic walruses are Polar bears (Ursus Maritimus) and Orca whales (Orcinus Orca). The young walruses are the only individuals at risk, though. Not even a killer whale will risk its life to try and hunt a mature Atlantic walrus. Although walruses are smaller than the whales, they still pose a very significant threat to the orca. Polar bears are the same way; they will not attack an adult walrus. The bears only kill infants, and even this is a challenge sometimes, as mothers will give their lives to protect the calves.