Grizzly Bears
Grizzly Bear (Ursus arctos horribilis) A symbol of America's wildlands, the grizzly or brown bear is one of the largest North American land mammals. The grizzly bear's historic range covered much of North America from the mid-plains westward to California and from central Mexico north throughout Alaska and Canada. Today, the grizzly bear is found in only about 2 percent of its original range in the lower 48 states. more info
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Grizzly and Wolf Discovery Center
A not-for-profit educational preserve protecting grizzly bears and gray wolves for research purposes. Come photograph, video and view these animals in a natural setting.
(800) 257-2570
Between 1800 and 1975, grizzly bear populations in the lower 48 states decreased from estimates of more than 50,000 to less than 1,000. The grizzly was eliminated
from much of the West by the late 1800s. As mountainous areas were settled, development contributed to an increase in human-caused mortality. Livestock depredation
control, habitat deterioration, commercial trapping, unregulated hunting, and the perception that grizzlies threatened human life were leading causes of the animal's
decline.
Today the Yellowstone population, residing in portions of Idaho, Montana, and
Wyoming currently contains an estimated 400-600 individuals. The grizzly bear
was listed as Threatened under the Endangered Species Act in 1975, with
primary management under the direction of the US Fish and Wildlife Service.
After delisting, the states would assume the primary management role within
their respective state boundaries.
Grizzly bears need a very large home range (50 to 300 square miles for females; 200 to 500 square miles for males),
encompassing diverse forests interspersed with moist meadows and grasslands in or near mountains. In the spring, bears usually range at
lower elevations and go to higher altitudes for winter hibernation.
Larger than the black bear, male grizzly bears stand about 7 feet tall and weigh from 300 to 600 pounds (and occasionally more than 800).
Females are smaller, usually weighing between 200 and 400 pounds. Although a standing grizzly is commonly perceived to be a threatening pose,
bears stand when they are simply curious or surveying their surroundings. Otherwise they generally remain on all fours.
Unlike the black bear, the grizzly bear has a rather concave face, high-humped shoulders, and long, curved claws. The grizzly's thick fur, which varies from
light brown to nearly black, sometimes looks frosty-looking, hence the name "grizzly," or the less common "silvertip." The grizzly has shorter, rounder ears than
the black bear.
Except for mating and caring for the young, grizzly bears primarily lead solitary lives, spending most of their time foraging, or looking for food. The grizzly is
North America's largest omnivore, meaning it eats both plants and other animals. About 80 to 90 percent of the grizzly's food is green vegetation, wild fruits
and berries, nuts, and bulbs or roots of certain plants. Grizzlies also eat a great deal of insects, sometimes tearing rotten logs apart and turning over heavy
stones in search of the insects themselves or their larvae.
Most of the meat in the grizzly's diet comes from animal carcasses, or carrion, of big game animals, although it will sometimes prey on elk or moose calves or
smaller mammals. For grizzlies along the west coast of Canada and in Alaska, salmon is an important food source.
The grizzly bear must eat enough to store huge amounts of fat needed to sustain it through its long winter sleep. The grizzly's ability to eat large quantities of rich
food and store fat without suffering from heart disease or cholesterol problems is of great interest to medical scientists. If scientists can determine how grizzlies
accomplish this, that information may be useful in preventing human heart disease.
At the top of the food chain, adult grizzly bears have little to fear from other wild animals. Grizzly cubs may fall prey to mountain lions, wolves, and other bears
if they stray too far from their mother.
Early in the fall, grizzly bears begin looking for a proper place to dig their dens, and may travel many miles before finding a suitable area. Generally, they seek
a high, remote mountain slope where deep snow will lie until spring to serve as insulation. Grizzlies often dig beneath the roots of a large tree to create their dens.
Obstructing roots are chewed up, and loose rocks and earth are thrust through the narrow entrance by the powerful strokes of the grizzly's forepaws.
The grizzly bear will generally enter its den in October or November. During the next 5 to 6 months, the grizzly will get no water or nourishment of any kind but will use
up its accumulated fat.
Male grizzly bears usually emerge from the den in March or April, while females emerge in late April and May. When a grizzly comes out of its den, the first food is
sometimes carrion from animals that did not survive the winter. A grizzly will usually travel to lower elevations to reach vegetated areas. Mating season is from June
through July. Grizzly bear embryos do not begin to develop until the mother begins her winter hibernation, although mating may have taken place up to 6 months before.
As with other bears, if the mother has not accumulated enough fat to sustain herself as well as developing cubs, the embryos may not implant (develop).
In January, usually one to three cubs, each weighing only a pound or less, are born. The cubs gain weight quickly and often have reached 20 pounds by the time they
come out of the den. As many as half of all cubs may not reach breeding age -- a leading reason for the grizzly's low numbers.
Cubs remain dependent upon their mother's milk for almost a year, stay with their mother for to 2 to 3 years, and reach breeding maturity at about 4 1/2 to 5 1/2 years.
In some cases they may not breed until 8 1/2 years of age. When they do reach breeding age, females only breed every 3 or more years. Males compete with each
other for breeding opportunities and seek females each year. Grizzlies usually live to be 15 to 20 years of age, and a few survive for up to 30 years.
- contains info from the US Fish & Wildlife Service
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