Grizzly Bear Predation on Elk Calves and Other Fauna of Yellowstone National Park

Success rate, frequency, chronology, and techniques of grizzly bear (Ursus arctos horribilis) predation on elk calves (Cervus elaphus) were determined from visual observations in the Pelican Valley area of Yellowstone National Park, 1984-88. Seventy hunts directed toward elk groups containing calves were recorded, 26 of which were successful. Twenty-one, 13, and 4 percent of all grizzly bear sightings in May, June, and July, respectively, involved hunts toward cow/calf groups. Success was significantly correlated with the number of attempts and the time of year. Grizzly bears were successful in killing calves in 71%, 42%, and 7% of the observed hunts in May, June, and July, respectively. Grizzly bears used 3 different techniques to hunt elk calves. Attempted predation on adult elk and other fauna was also observed.