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Friday, Jan. 11, 2002

ANIMAL TRACKER

Northern fur seal


ROLF REAM PHOTO/NATIONAL MARINE MAMMAL LABORATORY

* Japanese name: Kita-ottosei
* Scientific name: Callorhinus ursinus
* Description: Fur seals have bodies streamlined for life in the sea. They have four limbs (unlike dolphins and whales, which have only two), but the arm and leg bones are relatively short and are contained within the body. The hand and foot bones are elongated and webbed for improved swimming power, and the hind flippers can rotate, enabling the seals to run or climb on land. The penis and the testes are internal, and the nipples can be retracted to reduce drag. Adult males grow up to 2.1 meters long, and females 1.4 meters. Pups (see photo) are 60 cm long when they are born. Fur seals look black when they are wet, but males may be brownish-gray or reddish-brown, and females silvery-gray with a white patch on their chest.
* Where to find them: In the north Pacific, from the Bering Sea in the east, to Honshu and Hokkaido in the west. Males secure territories on the shore before the females arrive to give birth. Within 48 hours of giving birth, the females mate again.
* Food: Fish and squid. Fur seals hunt at night. Their whiskers are extremely sensitive to vibrations and are used to track prey. Their predators include foxes, sharks and killer whales.
* Special features: The fur of northern fur seals is incredibly thick, forming a dense waterproof coat containing over 60,000 hairs per square centimeter. This insulation allows them to live and hunt in cold and deep-water environments. Their nostrils shut automatically on diving, and their blood contains 3 1/2 times the hemoglobin (the oxygen-carrying molecule in red blood cells) of human blood. Fur seals often have to sleep in the open sea. Sleep is unihemispheric, which means that each half, or hemisphere, of the brain sleeps alternately. Hunting, for fur and for their perceived medicinal properties, has lead to the seal being classified as "vulnerable" in Japan. Tokugawa Ieyesu reputedly ate fur-seal extracts for vigor. Male fur seals are particularly vigorous. They form harems of 20-30 (sometimes up to 100) females, and copulate with the females for a month without eating, losing about 25 percent of their body weight.



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