Thursday, March 1, 2007

Food Habits of the Grizzly Bears in Yellowstone National Park

From March through May, ungulates, mostly elk and bison, comprise a substantial portion of a grizzly bear's diet. Grizzly bears feed on ungulates primarily as winter-killed carrion but also through predation of elk calves. Grizzly bears also dig up pocket gopher caches in localized areas of the park where thy are particularly abundant. Other items consumed during spring include grasses and sedges, dandelion, clover, spring-beauty, horsetail, and ants. Grizzly bears also feed extensively on whitebark pine nuts stored in red squirrel caches, especially during springs when an abundance of pine nuts have been left over from the previous fall.
From June through August, grizzly bears continue to consume grasses and sedges, dandelion, clover, spring-beauty, whitebark pine nuts, horsetail, and ants. In addition, thistle, biscuitroot, fireweed, and army cutworm moths are eaten. Predation on elk calves continues until late-June/early-July when grizzly bears are no longer able to catch calves. In areas surrounding Yellowstone Lake, bears feed extensively on spawning cutthroat trout. Starting around midsummer, grizzly bears begin feeding on strawberry, globe huckleberry, grouse whortleberry, and buffaloberry. By late summer, false truffles, bistort, and yampa are included in the diet, and grasses, sedges, and dandelion become less prominent.
From September through October, whitebark pine nuts are the most important bear food. Other items consumed during fall include: pond wee root, sweet cicely root, grasses and sedges, bistort, yampa, strawberry, globe huckleberry, grouse, whortleberry, buffaloberry, clover, horsetail, dandelion, ungulates, ants, false truffles, and army cutworm moths.
*Source: Information Paper No. BMO-3, Bear Management Office, Yellowstone National Park, Mark J. Biel, Bear Management Technician, March 2000.

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