polar bear(redirected from Polar bears)
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polar bear,large white bearbear,
large mammal of the family Ursidae in the order Carnivora, found almost exclusively in the Northern Hemisphere. Bears have large heads, bulky bodies, massive hindquarters, short, powerful limbs, very short tails, and coarse, thick fur.
..... Click the link for more information. , Ursus maritimus, formerly Thalarctos maritimus, of the coasts of arctic North America, Asia, and Europe. Polar bears usually live on drifting pack ice, but sometimes wander long distances inland. They are powerful swimmers and may cross 20 to 30 mi (30–50 km) of water at a time.
The polar bear's body is long and streamlined, with a long neck and small head. Adult males are 7 to 9 1-2 ft (210–290 cm) long, stand 4 to 4 1-2 ft (122–137 cm) at the shoulder, and weigh 700 to 1,600 lbs (320–730 kg). Females are somewhat smaller. The extremely dense fur appears yellowish white but is in fact unpigmented. Unlike other bears, polar bears have hairy soles, which help them grip the ice. They may attain a running speed of 25 mi (40 km) per hr on ice.
Polar bears are omnivorous, but feed chiefly on marine animals such as seals and young walruses. Quite fearless, they will stalk any animal, including humans. They take advantage of carcasses left by hunters, and in summer eat vegetation on the shore. If food is scarce, their physiology can slow to a state known as walking hibernation.
Except for a brief courtship in summer, polar bears are solitary. Males and nonpregnant females are thought to wander all winter. A pregnant female makes a winter den in the snow; two tiny, helpless cubs are born in January and nursed in the den until March. They usually remain with the mother for about a year and a half, while learning to hunt.
Polar bears have been extensively hunted, especially by Eskimos, for fur, flesh, and ivory, and they have declined greatly in numbers. Although extremely dangerous to humans, they do well in captivity. In recent years, changes in sea ice cover in the Arctic appears to have placed some populations of polar bears under stress, and has led the U.S. government to list the bear as threatened. Polar bears can crossbreed in the wild and in captivity with grizzly bearsgrizzly bear
large, powerful North American brown bear, characterized by gray-streaked, or grizzled, fur. Grizzlies are 6 to 8 ft (180–250 cm) long, stand 3 1-2 to 4 ft (105–120 cm) at the humped shoulder, and weigh up to 800 lb (360 kg).
..... Click the link for more information. . Polar bears are classified in the phylum ChordataChordata
, phylum of animals having a notochord, or dorsal stiffening rod, as the chief internal skeletal support at some stage of their development. Most chordates are vertebrates (animals with backbones), but the phylum also includes some small marine invertebrate animals.
..... Click the link for more information. , subphylum Vertebrata, class Mammalia, order Carnivora, family Ursidae.
See study by A. E. Derocher (2012).
(Ursus maritimus), a predatory mammal of the bear family; a typical representative of arctic fauna. Polar bears live in the region of floating ice near the Asiatic and American shores of the Arctic Ocean. They are larger than the European brown bear (body length, to 3 m; weight, about 700 kg). The fur is white (with yellowish spots), thick, and long. The soles of the feet are covered with hair.
Polar bears do not hibernate; however, pregnant females hole up in the winter in dens situated on the shore. The bears are excellent swimmers and divers. Their main food is the seal. They usually mate in July; the cubs are born, most often in pairs, in February or March. At birth they are blind and helpless. After a month, when they open their eyes, the female leaves the den and returns to a nomadic way of life. The cubs stay with the female about a year and a half. The bears give birth once every other year. Polar bears are hunted for their hides, which are made into rugs; and for their meat, which is edible. Hunting polar bears is completely forbidden in the USSR; in other countries it is restricted.