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People often confuse grizzly bears with black bears due to the fact that they share much of the same range. Although similar, they are two separate species. Grizzlies can actually grow to be larger than black bears, although their coloration may be similar according to Peterson’s First Guide to Mammals.
Grizzly bears have longer claws than black bears and their heads are larger in proportion to their bodies. Perhaps the most distinguishing feature of the grizzly is the hump, or roach, on its back gives the grizzly a great deal of strength in its forelegs, according to The Bears of Yellowstone, by Paul Schullery. However, full-grown black
bears can climb trees, whereas grizzlies cannot. Adult male grizzlies can weigh 800 pounds and females are about half that size.
Bears are omnivorous creatures, and grizzlies are no exception. While they mainly eat vegetation, bears will eat carrion, and small or weak animals. Bears living near the coast will consume fish in season. Grizzlies will forage over a range as large as 1000 square miles, according to the Official World Wildlife Federation Guide to Endangered Species. This depends largely upon the availability of food and where food is abundant. A
grizzly will have a much smaller range.
Grizzlies are solitary animals except when mating or rearing cubs. Mating takes place in late spring. By the time the female bear has hibernated, fertilization will have taken place. Cubs are born in late January or early February and weigh about one pound. When they leave the den in early spring, cubs weigh between five and ten pounds.
In preparation for hibernation grizzlies must consume enough food to gain a layer of fat, which can be up to eight inches thick in some places. This fat serves as energy during hibernation as well as insulation. Bears hibernate approximately four months, and they are the only mammals known to retain bone mass after a prolonged period of immobility. Humans, by comparison, would develop osteoporosis, according to The Bears of Yellowstone.
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