BIO 203


Living in such a wide stretch of wilderness, you would think that a grizzly bear is solitary and wouldn’t interact too often with other organisms. In fact, there are key interactions that influence a grizzly bear. Most of these interactions are one-sided with the grizzlies out-competing the other organisms, except for the case with humans. Rarely do any conflicts result in death by either organism.

Black Bears

Black bears are the most common competitor with grizzlies. They inhabit the same areas in the southern end of the grizzly bear range, such as Yellowstone National Park, and have similar herbivorous diets. Because black bears are generally smaller, they will either run or climb a tree to avoid confrontation with grizzlies. Due to their large size and greater need for resources, grizzlies out-compete black bears and can drive them out of their territory.


Competition between wolves and grizzlies has increased since the reintroduction of gray wolves to Yellowstone National Park in 1995 (Fortin et al. 2013). Most conflict occurs when a grizzly is scavenging for food and comes across wolves with their kill. The wolves may try to defend their kill if there are enough in the pack, or else they may leave it behind because it is not worth the risk to fight off a grizzly for minimal food.



Squirrels are scavengers of nuts, and they store their resources in their nests. Grizzlies are also scavengers and will eat nuts if they are readily available. Grizzlies will sometimes scavenge squirrel nests and eat the nuts that the squirrels have collected. If the squirrels are hibernating, they may be eaten as well.


With the human population ever expanding, they are crowding out the natural habitat of the grizzly bears through urbanization. Places such as Yellowstone National Park have also become popular tourist attractions causing a lot contact between the two, especially during summer months: the peak time of tourism and grizzly bear activity.


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