 Aside from humans , no species <unk> upon mature cougars in the wild , although conflicts with other predators or scavengers occur . The Yellowstone National Park ecosystem provides a fruitful <unk> to study inter @-@ predator interaction in North America . Of the three large predators , the massive grizzly bear appears dominant , often although not always able to drive both the gray wolf pack and the cougar off their kills . One study found that American black bears visited 24 % of cougar kills in Yellowstone and Glacier National Parks , <unk> 10 % of carcasses . Bears gained up to 113 % , and cougars lost up to 26 % , of their respective daily energy requirements from these encounters . Accounts of cougars and black bears killing each other in fights to the death have been documented from the 19th century . In spite of the size and power of the cougar , there have also been accounts of both brown and black bears killing cougars , either in disputes or in self @-@ defense . 
