Elk are a keystone species of Yellowstone National Park. Elk serve as a predominant food source for many other large mammals in the area. These mammals include grizzly bears, coyotes, black bears, and golden eagles. In addition, mountain lions affect the elk population in the northern section of the park. If elk were removed from the park or the population were to decrease, the populations of the elk’s predators would be affected. For example, if the population of elk were decreased by disease or natural disaster, wolves and coyotes, would experience difficulty finding elk to feed on.