Grizzly Bear

The Grizzly Bear (*Ursus arctos horribilis*) is a bear inhabiting North America.

The Ussuri brown bear (*U. a. lasiotus*), inhabiting Russia, China, Japan, and Korea, is sometimes referred to as the "black grizzly"

Appearance

Although variable in color from blond to nearly black, grizzly bear fur is typically brown with darker legs and commonly white or blond tipped fur on the flank and back.

Range and population

Brown bears are found in Asia, Europe, and North America, giving them the widest range of any bear species. They also inhabited North Africa. In North America, grizzly bears ranged from Alaska down to Mexico and as far east as the western shores of Hudson Bay; the species is now found in Alaska, south through much of western Canada, and into portions of the northwestern United States (including Washington, Idaho, Montana and Wyoming), extending as far south as Yellowstone and Grand Teton National Parks. In Canada, there are 25,000 grizzly bears occupying British Columbia, Alberta, the Yukon, the Northwest Territories, Nunavut, and the northern part of Manitoba.

Hibernation

Grizzly Bears hibernate for 5 to 7 months each year. To prepare for hibernation, grizzlies must build a den, and consume an immense amount of food as they do not eat during hibernation. The male grizzly bear's hibernation ends in early to mid-March, while females emerge in April or early May.

In preperation for Winter, bears can gain a period of hyperphagia, before going into hibernation. The bear waits for a snowstorm before it enters its den, such behavior lessens the chances predators will find the den. In some areas where food is very plentiful year round, grizzly bears skip hibernation altogether.

Diet

Grizzlies are of the order Carnivora and have the digestive system of carnivores, they are normally omnivores: their diets consist both plants and animals. They have been known to prey on large mammals, when available, such as moose, elk, white-tailed deer, bighorn sheep, bison, and even black bears, though they are more likely to take calves rather than healthy adults. Grizzly bears feed on fish such as salmon, trout, and bass, and those with access to a more protein-enriched diet in coastal areas potentially grow larger than inland individuals. Grizzly bears also readily scavenge food or carrion left behind by other animals. Grizzly bears will also eat birds and their eggs, and gather in large numbers at fishing sites to feed on spawning salmon. They prey on baby deer left in the grass, and they raid the nests of raptors such as bald eagles.

Meat, as already described, is an important part of a grizzly's diet. Grizzly bears prey on small mammals, such as marmots, squirrels, lemmings, and voles. The most famous example of such predation is in Denali National Park and Preserve, where grizzlies chase, pounce on, and dig up Arctic ground squirrels to eat. In some areas, grizzly bears prey on marmots, overturning rocks to reach them, and in some cases preying on them when they are in hibernation. Larger prey includes bison and moose, which are sometimes taken by bears in Yellowstone National Park. Because bison and moose are dangerous prey, grizzlies usually use cover to stalk them and/or pick off weak individuals or calves. Grizzlies in Alaska also regularly prey on moose calves, which in Denali National Park may be their main source of meat. In fact, grizzly bears are such important predators of moose and elk calves in Alaska and Yellowstone that they may kill as many as 51 percent of elk or moose calves born that year. Grizzly bears have also been blamed in the decline of elk in Yellowstone National Park when the actual predators were thought to be gray wolves. In northern Alaska, grizzlies are a significant predator of caribou, mostly taking sick or old individuals or calves. Several studies show that grizzly bears may follow the caribou herds year-round in order to maintain their food supply. In northern Alaska, grizzly bears often encounter muskox. Despite the fact that muskox do not usually occur in grizzly habitat and that they are bigger and more powerful than caribou, predation on muskox by grizzlies has been recorded.