The Big Dry Arm Spring Storm in the Great Basin Red Cliffs Desert Tortoise Reserve March Morning on the Platte River After a Spring Storm in the Great Basin Hunting Upland Birds at Kingsbury Lake Waterfowl Production Area Sandhill Migration on the Platte River Badlands Sunrise The Green River at Ouray NWR North Park Lupines Moab Sunset
Endangered Species | Mammals
Mountain-Prairie Region
Graphic button showing the 8 state mountain prairie region

Grizzly Bear

 

A close-up picture of an adult Grizzly Bear, angled to prominently show the bear's neck and snout

Grizzly bear (Ursus arctos horribilis)

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Taxon: Mammal

Range: ID, MT, WA, WY

Status: Threatened



Species History, Habitat, and Diet

History

When Lewis and Clark explored the West in the early 1800s, grizzly bears roamed across vast stretches of open and unpopulated land between the Pacific Ocean and the Great Plains. But when pioneers moved in, bears were persecuted and their numbers and range declined. As European settlement expanded over the next hundred years, towns and cities sprung up, and habitat for these large omnivores—along with their numbers—shrunk drastically. Of the many grizzly populations that were present in 1922, only six remained when they were listed by the Service in 1975 as a threatened species in the lower-48 states.

General Habitat Requirements

Good grizzly bear habitat provides all the components necessary for the species’ survival: food, cover, a place to den, solitude, and plenty of space. Prime grizzly bear habitat features a diversity of plants, which provides bears with a varied food supply of plants, insects, and animals.

Today, grizzly bears are only found in large tracts of relatively undisturbed land, and a clear relationship exists between the loss of grizzly bears and the destruction or fragmentation of their habitat. Bear researchers agree that the most crucial element in grizzly bear recovery is to secure adequate habitat.

The home range for one grizzly bear may encompass up to 600 square miles, so space is essential. Because grizzly bears can come into conflict with humans and our uses of the land, such as ranching or recreation, good bear habitat must offer some areas that are isolated from development or otherwise highly impacted by humans.

Roads likely pose the most imminent threat to grizzly habitat today, and the management of roads is one of the most powerful tools available to balance the needs of people with the needs of bears. In addition, the impacts of logging, mining, livestock grazing, and various forms of outdoor recreation in grizzly habitat can be mitigated through well-designed management programs.

Diet

Like humans, the grizzly bear is omnivorous and scavengers by nature, spending most of their waking hours searching for food. Grizzly bears are adaptable and may eat insects, a variety of flowering plants, roots, tubers, grasses, berries, small rodents, fish, carrion (roadkill and other dead animals), other meat sources (e.g. young and weakened animals), and even human garbage if it is easily accessible.

Grizzly bears are active and feeding for six to eight months in the spring, summer and fall of every year. During this time, they must consume large amounts of food in order to survive the winter. Bears in each ecosystem learn where and when particular foods are available through their personal experiences, and because of this, biologists have been able to learn and generally predict their seasonal distribution and movement.

Food Habits Through the Seasons

Grizzly bears emerge from their dens in the spring, between late March through May, when young vegetation begins growing. During the early months they move out of the snow to low elevation areas to feed on winter-killed animals, ants, grasses and sedges, clover, dandelion, cow parsnip, and other plants.

In the summer months of June through August, grizzly bears continue to eat flowering plants and dig for roots, tubers, and insects. Common summer food sources are thistle, fireweed, mushrooms, and moths in Yellowstone. In some areas, bears may prey for a few weeks on newly born elk, deer, and bison calves, until the young animals become too fast to be captured. In late summer, berry-producing shrubs provide a preferred food in some ecosystems.

In September and October, grizzly bears spend more and more time searching for food and eating. Berries, whitebark and limber pine nuts, insects, and starchy tubers and roots are important food sources that allow them to build up the fat reserves they need for winter hibernation, which begins in late October or November.

Whitebark Pine

Grizzly bears in the Greater Yellowstone Ecosystem also enjoy whitebark pine cone seeds where they overlap with their home range, and some conservationists have questioned whether an abundant supply of whitebark pine was necessary for the survival of bears in this ecosystem. Research indicates that as opportunistic feeders, Yellowstone grizzly bears can maintain healthy population levels even with varying availability of whitebark pine.

For information on living and recreating in grizzly bear country, visit the Interagency Grizzly Bear Committee’s bear safety page.

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The mission of the U.S. Fish and Wildlife Service is working with Others to conserve, protect, and enhance fish, wildlife, plants and their habitats for the continuing benefit of the American People.
Last modified: June 05, 2019
All Images Credit to and Courtesy of the U.S. Fish and Wildlife Service Unless Specified Otherwise.
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