Grizzly Bear

Grizzly Bear


Grizzlies are generally loners, but they are still North America’s most social bear. They  gather at food sources and often forage in family groups. Large adult males will aggressively defend their place at the head of their social circle, but grizzlies are not territorial and their home ranges often overlap. Home territories vary in size depending on location, but in Yellowstone National Park, they average 50 square miles. 

Bears usually hibernate from late fall to spring, but those in warmer regions may stay active through the winter. Each year they may return to the same den, which is usually within a sheltered slope, under a large rock, or within the roots of a large tree. Grizzlies can be unpredictable when startled—especially if they feel that cubs or food are threatened.


For such big animals, grizzlies usually chow on the small stuff: berries, grasses, roots, bulbs, tubers, and insects. They also eat small mammals and carrion. Bears in the Canadian Rockies are known to hunt larger prey, such as mountain goats, elk, moose, and even black bears. Grizzlies in northwestern America gather at salmon streams during the summer to catch fish migrating upstream to spawn. 

Life Cycle

Female grizzlies usually give birth to two cubs during hibernation in January or February. The newborns are blind, hairless, and tiny—weighing less than a pound. They stay in their dens until springtime, when they have reached about 20 pounds. Once they are out in the world, they remain with their mother for at least two years more. Their average lifespan in the wild is 25 years, but grizzly bears have lived as long as 50 years in captivity.

Some of My Neighbors

Elk, Moose, Cougars, Gray Wolves, Black Bear, Coyote, Dall’s Sheep

Population Status & Threats

Grizzly bears are currently found in only 2 percent of their historic range within the U.S. In the early 1800s, an estimated 100,000 grizzlies lived in the western United States (excluding Alaska), but their numbers declined greatly as settlers moved west. Logging, mining, and road construction further reduced grizzly numbers by destroying their habitat. Today, there are about 1,000 of these bears in Montana, northern Idaho, northeastern Washington, and Wyoming. In Alaska, the grizzly bear population is estimated at 30,000.

WCS Conservation Efforts in Grizzly Range

The grizzly bears that live in the Bronx Zoo are part of a unique conservation intervention by the Wildlife Conservation Society. The bears had been encroaching on human habitat—a problem that leads to all sorts of conflicts in places throughout the world where animals and people share their turf. As a result of being nuisance bears,” they faced possible euthanization. Working together with the U.S. Fish and Wildlife Service (FWS), the zoo was able to provide a refuge for the bears.

WCS field conservationists based in the Greater Yellowstone Ecosystem are monitoring energy development projects, predator-prey dynamics, and human-wildlife conflicts across the landscape to protect grizzly bears and other Western wildlife species. WCS Canada operates the Yellowstone-to-Yukon initiative. This field program seeks to repair habitat fragmentation and maintain an interconnected ecoregion that can support the grizzly bear and other wide-ranging animals.

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