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Grizzly And Other Brown Bears

Brown or grizzly bears (Ursus arctos) live in forest, tundra, and grassland across the top of the Northern Hemisphere, including both North America and Eurasia. Some biologists separate them into three subspecies: the Eurasian brown bear (U. a. arctos) of much of temperate and subarctic Eurasia; the grizzly bear (U. a. horribilis) of Canada, Russia, and the United States; and the Kodiak bear (U. a. middendorffi) of Kodiak Island and two smaller islands in the Bering Sea off Alaska. These various brown bears may vary in color from white to cinnamon to black, but their fur is most commonly brown. Some brown bears have white tips on the end of the hairs, a coloring called grizzled. A grizzly bear can be distinguished from other bears in North America by the profile of its body. The outline of its head as seen from the side is concave, or scooped inward, and its shoulders are high due to a thick layer of muscle and fat, which makes the back appear to slope downward.

Grizzlies that live near rivers accessible to the ocean feed on migrating salmon as much as they can. Those bears that feed well can be huge in size. Even with their great size, they like to frolic in the water and are adept at catching fish, which they carry to land to strip the flesh from the bones. They may also hunt rodents, and will opportunistically predate large prey such as moose, caribou, and even black bears. When meat is not available, grizzlies feed primarily on roots, sedge leaves, and berries.

Grizzly bears mate in the late spring. In the autumn, the sow finds a den in a cave or hollow tree, and settles in for her winter lethargy. Two or three cubs are born, usually in February. The cubs stay close to their mother for at least two years, continuing to nurse during most of that time. The mother is exceedingly protective, and teaches the cubs to climb trees to escape danger. Most attacks on humans are made by sow grizzlies protecting their cubs. One of the major enemies from which she must defend her cubs is male grizzlies, which will kill and eat them.

After a young female leaves its mother, it may continue to share the same feeding range. A male, however, will go off on its own, traveling up to 100 mi (160 km) before finding a place to settle down. It may have difficulty finding a suitable habitat because older males will fight to keep new ones out of their territory.

The range of the grizzly bear originally extended from Alaska to Mexico, as far east as Hudson Bay, through the prairie region, and even extending into desert habitat. Grizzlies have now disappeared from most of the western United States, with only small numbers surviving in Wyoming, Montana, Idaho, and Washington. There are larger numbers in Alberta, British Columbia, Yukon, Alaska, and the Northwest Territories. The populations of grizzlies in the United States (outside of Alaska) have declined mostly because of excessive hunting and habitat loss. These are still important problems for the species.

Eurasian brown bears vary greatly in size. The few remaining in Spain rarely weigh more than 250 lb (114 kg). Those in Siberia may rival the huge Kodiak bear in size. Brown bears are still found throughout much of Europe and Asia, but in rapidly decreasing numbers because of excessive hunting and habitat loss. Those that survive live primarily in hardwood forest in mountainous regions. Fewer than 35,000 brown bears are thought to live in Eurasia.

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Science EncyclopediaScience & Philosophy: Ballistic galvanometer to Big–bang theoryBears - Grizzly And Other Brown Bears, Polar Bear, American Black Bear, Other Black-colored Bears