The grizzly bear, a subspecies of the brown bear (Ursus arctos), is one of the largest land mammals in North America. An average male grizzly has a head and body length of 6 to 8 feet (1.8 to 2.4 meters), stands 3.5 to 4 feet (1 to 1.2 meters) at its shoulder, and may weigh up to 800 pounds (360 kilograms).
The smaller female grizzly weighs between 200 and 400 pounds (90 and 180 kilograms). The grizzly bear is so-named because its thick, light brown to black fur is streaked with gray, giving it a “grizzled” look. Grizzly bears have short, rounded ears, humped shoulders, and long, curved claws.
Although grizzly bears are omnivores (they eat both plants and animals), most of their diet consists of vegetation: fruits, berries, nuts, and the bulbs and roots of plants. They also eat ants and other insects.
The meat in a grizzly bear’s diet comes from deer or smaller mammals such as elk or moose calves. Salmon makes up a large part of the diet of grizzly bears that inhabit Alaska and the west coast of Canada.
Grizzly bears store large amounts of fat, which their bodies rely on during their long winter hibernation. Grizzlies build their dens in early fall, often on high, remote mountain slopes underneath the roots of large trees. Once they enter their dens in October or November, they do not emerge for five or six months (females usually emerge one month after the males in the spring).
Male and female grizzly bears usually mate in June or July. After a gestation (pregnancy) period of about six months, a female grizzly gives birth during hibernation to one to three cubs.
The infant bears usually weigh 1 pound (.45 kilogram) at birth, but gain as much as 20 pounds (9 kilograms) by the time spring arrives. Female grizzlies nurse their cubs for up to one year, and the cubs remain with their mother for two to three additional years. The average life span of a grizzly bear is 15 to 20 years.
Habitat and current distribution
In the contiguous United States (the connected 48 states) in the early 2000s, there are five known grizzly bear populations in the states of Idaho, Montana, Washington, and Wyoming. The largest is in Yellowstone National Park (Idaho, Montana, Wyoming) with 400 to 600 bears.
Three populations are in Glacier National Park (Montana and Idaho): Northern Continental Divide with 300 to 400 bears; Selkirk with 45 to 50 bears; and Cabinet-Yaak with 30 to 40 bears. A tiny population remains in North Cascades National Park (Washington) with 5 to 30 bears.
Wildlife biologists (people who study living organisms) estimate there are over 20,000 grizzly bears in western Canada and over 30,000 in Alaska (where they are called brown bears). British Columbia is currently home to about half of Canada’s grizzlies.
History and conservation measures
Grizzly bears used to range over the entire western half of North America, from Mexico up to the Arctic Circle. In 1800, the grizzly bear population in North America exceeded 50,000. By 1975, that number had been reduced to less than 1,000.
Habitat destruction and hunting are the two main reasons for this drastic decline. As pioneers moved west during the nine-teenth century and settled mountainous regions, grizzly bears were forced out of their natural habitat. These pioneers also shot and trapped grizzlies, believing the animals posed a threat.
As the wild areas of the American west continue to be developed (such as with the building of recreation areas), the survival of grizzly bears will continue to be jeopardized. Even though they are protected by laws, grizzlies are still shot by hunters who mistake the animals for black bears.
During the last decades of the twentieth century, the U.S. government worked with state agencies and Native American tribes in an effort to manage and protect grizzly bear habitat.
These efforts were highly successful in areas such as the Yellowstone National Park ecosystem (the system of plant, animals, and microorganisms within their environment), where the grizzly bear population exceeded target levels in the last years of the 1990s.
At the turn of the twentieth century, considerable controversy arose over plans to reintroduce grizzlies to Idaho’s Bitterroot Mountain ecosystem. The area was once home to a significant population of grizzlies, but none remain in modern times.
Because the habitat is so well suited to a recovery program, the U.S. Fish and Wildlife Service developed a detailed reintroduction plan—worked out over six years with the residents and industry representatives of the affected areas in the Bitterroots.
In June 2001, however, the secretary of the interior of the United States announced that the plan was to be abandoned. Many wildlife conservationists (people who work to manage and protect nature) protested this disruption in the recovery of the grizzly bear.