Grizzly Bear Nutrition and Ecology Studies in Yellowstone National Park

THE CHANCE TO SEE a wild grizzly bear is often the first or second reason people give for visiting Yellow-stone National Park. Public interest in bears is closely coupled with a desire to perpetuate this wild symbol of the American West. Grizzly bears have long been described as a wilderness species requiring large tracts of undisturbed habitat. However, in today’s world, most grizzly bears live in close prox-imity to humans (Schwartz et al. 2003). Even in Yellowstone National Park, the impacts of humans can affect the long-term survival of bears (Gunther et al. 2002). As a consequence, the park has long supported grizzly bear research in an effort to understand these impacts. Most people are familiar with what happened when the park and the State of Montana closed open-pit garbage dumps in the late 1960s and early 1970s, when at least 229 bears died as a direct result of conflict with humans. However, many may not be as familiar with the ongo-ing changes in the park’s plant and animal communities that have the potential to further alter the park’s ability to support grizzly bears. These changes include the decline in Yellowstone Lake cutthroat trout due to the unplanned introduction of the pre-daceous lake trout, the spread of whirling disease, and a long-term drought (Koel et al. 2004; McIntyre 1996). Cutthroat trout have been consumed for thousands of years by grizzly bears from mid-May to mid-August, when they spawn in the small streams that flow into Yellowstone Lake (Haroldson et al. 2005). Whitebark pine, one of the most important fall foods of the grizzly bear, is infected with an exotic fungus, white pine blister rust. The high-fat, energy-rich whitebark pine nuts are consumed during the fall when the crop is limited or durin