Objectives:
The student will . . .

• Identify the main food sources of the grizzly bear in Yellowstone National Park.

• Recognize various food types through seasonal changes.

Background:
Grizzlies will eat almost anything. Like all bears, they are part of a group of animals called carnivores, which means meat-eating. However, in most places, grizzlies are not active hunters, eating meat only when it is easy for them to do so. In fact, up to 90 percent of their diet may be plants, including leaves, stems, and roots.

Overall, the most important foods in the grizzly bear's diet at Yellowstone National Park are whitebark pine nuts, graminoids, and ungulates. Grizzly bear food habits are influenced by seasonal variation in available food. The student handout describes the seasonal diets of Yellowstone's grizzlies.

Procedure
Following the Electronic Field Trip, the teacher will . . .

• Share the background information with the students and distribute copies of the student handout.

• Instruct students to make a creative poster to illustrate the food habits of grizzly bears in Yellowstone National Park by season. This may be done electronically.

• Invite students to present their posters to the class.

Alternative: Students might wish to create a "Bear Restaurant" as a class project, producing one extensive grizzly menu!

Student Handout: Food Habits of the Grizzly Bears in Yellowstone National Park*

Spring

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.

Summer

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.

Fall

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.

Winter

(Hibernation)

*Source: Information Paper No. BMO-3, Bear Management Office, Yellowstone National Park, Mark J. Biel, Bear Management Technician, March 2000.

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