I have studied large carnivores for the last 26 years, focusing on puma ecology and human-puma interactions in Arizona, and the conservation and behavioral ecology of grizzly bears in the Yellowstone ecosystem of Wyoming, Montana, and Idaho. He spent 18 years intensively studying grizzly bear foraging behavior and diet as well as ecological relations of foods the bears ate. These studies revealed details about a broad spectrum of bear behaviors, including their bedding, use of rub trees, consumption of dirt and earthworms, exploitation of red squirrels, pocket gophers, and meadow mice, and predation on elk, moose, and trout.