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What grizzly bears eat

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Grizzly bears are omnivores with a rich and varied diet. They follow the Michael Pollan rule of diet: Lots of vegetables.

The tumbled stones left behind from grizzly bear digs for glacier lilies. Photo Chris Morgan

Ursus arctos, the grizzly/brown bear, is the most widely distributed bear of the eight species. For good reason.

Opportunistic omnivore

This species has evolved as a wonderful example of a true “opportunistic omnivore” that is able to adapt well to a whole host of potential food sources depending upon what’s available.

The brown bear’s range includes the Pakistani Himalayas where marmots are on the menu of the day (complemented with a side of sedge of course). In Spain, brown bears occupy mountainous beech and oak forests where nuts and acorns are the mainstay. On the Gobi Desert the brown bear doesn’t have it so good—there, wild celery and vegetation around seasonal watering holes are the scant offerings available.

Even in North America the grizzly bear’s diet varies immensely—from cutthroat trout, white-bark pine seeds, and elk in Yellowstone (where up to 40% of a bear’s diet might be deer meat), to army cutworm moths in Glacier National Park (40,000 of them on a good day!), and of course the prolific berry crops that are available here in the Pacific Northwest where everything from devils club to grouseberry provide essential seasonal fruits.

The photo at right shows bear ecologist Chris Morgan at digs created by grizzly bears searching out glacier lily roots. Grizzly bears use their claws primarily for digging carbo-rich roots and overturning rocks in search of oil-rich piles of ant grubs.

The Cascades smorgasbord (up to 90% vegetation) also includes ants and ant larvae, beetle larvae, flower heads, worms, winter-killed deer, skunk cabbage, horsetail, cow parsnips, succulent roots of a wide variety of plants, and hornets. When you’re a grizzly bear, it pays to be flexible.

Grizzly bears also rely on carrion, animals killed by wolves or cougar as well as winter-killed elk and deer. Grizzly bears in Yellowstone have benefited greatly from kills made by wolves.
Fantastic footage of bear wolf interactions in Yellowstone

Climate change

Warming climate allows mountain pine beetles to persist through the winter, killing off white-bark pines across the West come spring. White-bark pine seeds are a very important, oil-rich food source for grizzlies and a their loss a sore blow to grizzly bears. Yet the grizzly bear's varied diet and great adaptability will help buffer this versatile animal from the effects of a changing climate and loss of any one single food source.

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