PACIFIC WALRUS } Odobenus rosmarus divergens
DESCRIPTION: Walruses are easily distinguished by their long, white tusks, cinnamon-brown skin, grizzled whiskers, and bodies full of blubber. Growing up to 3,750 pounds, male Pacific walruses are larger than females and measure approximately 10 feet long. After a sustained period in very cold water, the tiny blood vessels in their skin constrict, and walruses appear almost white. Walruses turn pink when their circulation increases to diffuse excess body heat.
HABITAT: Walruses divide their time between shallow waters, where they search for food, and ice floes or land, where they get needed rest since they can’t swim continuously. They also haul out onto sea ice to give birth, socialize, and nurse young.
RANGE: The Pacific walrus is found in the arctic waters of the Bering and Chukchi seas between Alaska and Siberia, as well as the eastern Siberian Sea and western Beaufort Sea.
MIGRATION: Pacific walruses winter in the central and south Bering Sea and summer in the Chukchi Sea. Adult females and their young are migratory, following the sea ice edge north in the summer, while males remain in the south and haul out onto rocky beaches when the ice melts.
BREEDING: During the mating season, adult males make taps, knocks, pulses, and bell sounds underwater to attract females and show superiority. Fighting occurs between males who “joust” with their tusks. Mating takes place in the water; gestation lasts 15 to 16 months. Females give birth to a single calf once every two to four years. Calves nurse for two years yet spend up to five years with their mothers. Females are extremely protective, and calves often ride on their mothers’ backs in the water.
LIFE CYCLE: The maximum lifespan of a walrus is approximately 40 years.
FEEDING: Walruses eat clams, crabs, shrimp, soft corals, sea cucumbers, and various other mollusks. They use their extremely sensitive “whiskers” to identify food. Walruses seize their prey between their lips and suck mollusks out of their shells with a quick piston-like flick of the tongue. Adult walruses eat 5 percent of their body weight daily and they can eat 6,000 clams in a single feeding.
THREATS: Walruses face severe threats from global warming and the associated recession of arctic sea ice. The disappearance of sea ice is forcing walruses to haul out on land during the summer, which limits access to feeding areas at sea and makes them vulnerable to trampling, predation, and human disturbances. A major threat to the Pacific walrus is oil and gas exploration and drilling in the Chukchi and Bering seas. Other dangers include habitat disturbances, ocean acidification, and toxic pollution.
POPULATION TREND: Commercially exploited for centuries, Pacific walruses have been substantially reduced in numbers. Conservation measures were initiated in the United States and Russia, allowing the subspecies to rebound. Current trends indicate that numbers may again be declining, but exact population figures are unknown.