What Do Grizzly Bears Eat?
Interagency Grizzly Bear Committee (IGBC) Article -
The grizzly bear, like its cousin the black bear, is omnivorous, meaning it will eat plants, as well as insects and other animals. Scavengers by nature, grizzlies spend most of their waking hours searching for food. Forbs, roots, tubers, grasses, berries and other vegetation, and insects comprise most of the bear’s diet. But grizzlies are very adaptable, finding and subsisting on a variety of foods if necessary. The grizzly diet can include small rodents, fish, carrion, and even garbage and human food if it is easily available.
Food sources vary in availability from year to year, and from season to season. Grizzlies move throughout their habitat looking for foods available at that time of year. The availability of many foods is known to the bears by season, and the bears move to these areas based on their experience. In this way, the general seasonal distribution and movements of bears are predictable. Ingestion of large amounts of food in a short time period is critical to grizzly survival, since they are only active and feeding for 6-8 months of every year.
Grizzlies emerge from their dens from late March to May, whenever young vegetation begins growing. During the early spring months, bears move to low elevation areas, out of the snow, to feed on young, green vegetation. Common spring food sources include winter-killed animals, as well as ants, grasses and sedges, clover, dandelion, cow parsnip, and other plants.
From June through August, grizzly bears continue to eat forbs, dig for roots and tubers, and excavate insects, such as ants and grubs. Common summer food sources are thistle, fireweed, mushrooms, and moths clustering in rocky, high-elevations areas. 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. For a few weeks during the summer, bears in the Yellowstone ecosystem catch cutthroat trout in spawning streams around Yellowstone Lake and Henry’s Lake.