A symbol of America's wildlands, the grizzly or brown bear is one of the largest North American land mammals. Grizzly bears need a very large home range (50 to 300 square miles for females; 200 to 500 square miles for males). 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. Today, grizzlies can be found in Wyoming, Montana, Idaho, and Washington.
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.
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.
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.
How Fast Is a Grizzly Bear? Faster than we are. Weighing more than 1,600 pounds, a grizzly bear—the world's largest flesh-eating land mammal—is astonishingly swift for its size. Its speed comes, in part, from its strength. Some 300 pounds of muscle are concentrated in the animal's shoulders, back, and buttocks, enabling it to deliver more force to its limbs than a human can. In a sprint a grizzly can do 30 miles per hour. So how do these large, lumbering creatures manage to be so swift? To start with, bears are quadrupeds, which gives them an inherent advantage over bipeds like us. Since they can gallop, bears can achieve far more momentum than we can with our bipedal striding.
As they drag themselves forward with their front paws, bears gather their body into a compressed ball. Then their back legs drive down, their back straightens out, and they push off with their legs. This sort of lunging and gliding resembles a spring uncoiling and allows them to move quickly.
In 1975, the U.S. Fish and Wildlife Service listed the grizzly bear as a threatened species under the Endangered Species Act, meaning it is considered likely to become endangered ("endangered" means a species is considered in danger of extinction within all or a significant portion of its range).
Conservation Status: International Union for Conservation of Nature and Natural Resources Status: - Least Concern. Ecoregions containing Grizzly Bear (Ursus arctos horribilis). Habitat destruction in valley bottoms and riparian areas is particularly harmful to grizzlies because they use these "corridors" to travel from one area to another when they are searching for food. Some private landowners and companies are trying to help grizzlies by voluntarily protecting grizzly corridors. Some grizzly bears are accidentally killed by hunters who mistake them for black bears, which are legal game. But the biggest threat to the grizzly is human-caused mortality. Grizzlies become habituated to humans because of what biologists call "attractants," which include garbage, pet foods, livestock carcasses, and improper camping practices. This can eventually lead to conflicts between people and bears -- not only in populated areas of the grizzly's range but also in back country recreation sites.
The six ecosystems in the U.S. that have been identified by biologists as suitable for grizzly bears are: Yellowstone (northwestern Wyoming, southwestern Montana, and eastern Idaho), Northern Continental Divide (northwestern Montana), the Cabinet-Yaak (northwestern Montana), Bitterroot (central Idaho and western Montana), Selkirks (Idaho and eastern Washington), and the North Cascades (Washington).
The grizzly bear recovery effort has been met with some successes thus far. These successes have been largely due to a cooperative effort among several organizations called the Interagency Grizzly Bear Committee. Established in 1983, the committee includes the U.S. Forest Service; National Park Service; Bureau of Land Management; state agencies in Montana, Wyoming, Idaho, and Washington; Canadian wildlife management agencies; and Native American Tribes. The committee coordinates habitat management, research, and education and outreach for the grizzly bear.