Grizzly Bears In Yellowstone National Park

The Yellowstone ecosystem provides vital habitat for grizzlies in its two national parks (Yellowstone and Grand Teton), six national forests, state lands, and private lands. Some bears live either totally inside or outside of Yellowstone National Park; others may use portions of various different agency holdings.

Because grizzly bears range widely and are usually solitary, they are difficult to count. Biologists estimate their population within the Yellowstone ecosystem to be 280-610 bears.

The Yellowstone ecosystem is unique among areas inhabited by grizzly bears in North America because of the foods it provides. Here, grizzly bears depend more on animals, ranging from ants and moths to elk and bison. Bears here and elsewhere also eat large amounts of plants, but Yellowstone lacks the lush vegetation and berries found in northern Montana.

When Yellowstone grizzly bears emerge from hibernation in March and April, there is still a lot of snow and very little vegetation in most of the park. The bears move to the low country where elk and other ungulates (hoofed mammals) spent the winter. There, the bears feed on carcasses of ungulates that died during the winter. (Never approach a carcass—a bear may be nearby and it will often defend its food source.) Bears are not the only animal that depends on winter-killed ungulates for survival. Wolves, coyotes, wolverines, badgers, foxes, eagles, ravens, magpies, and carrion beetles also feed on the carcasses.

Grizzly bears prey on elk calves in the spring, usually from mid-May through early July. After early July, most elk calves can outrun bears. Some bears will feed on spawning cutthroat trout in the Yellowstone Lake area during the early summer. Bears also dig for small rodents (primarily pocket gophers), ants, roots, and tubers. Later in the summer, grizzly bears feed on army cutworm moths and whitebark pine nuts at high elevations. Despite their small size, these foods are important, high-protein foods for grizzly bears, especially as autumn approaches.

The restoration of wolves to the park appears to be providing bears more opportunities to obtain meat. During the years since the 1995 release of wolves into the park, bears have been observed successfully taking wolf-killed ungulates away from wolf packs. Will this new opportunity increase the grizzly bear population in Yellowstone? No one knows.

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