Grizzly Bear Predation on a Bull Bison in Yellowstone National Park

Wyman, Travis

Grizzly bears (Ursus arctos horribilis) will eat meat whenever it is available to them (Mattson 1997). Ungulate meat is more prominent in the diet of grizzly bears from the Yellowstone area than other interior brown bear populations in North America (Craighead and Mitchell 1982, Mattson et al. 1991, Mattson 1997). Nitrogen (N,5) isotope analysis of hair collected from grizzly bears in the Greater Yellowstone Area suggests that meat comprises almost half of the annual energy intake of adult females and over half for adult males (Jacoby et al. 1999). Grizzly bears obtain ungulate meat primarily through scavenging winter-killed (Green et al. 1997) and wolf-killed (Canis lupus; D. Smith, Yellowstone National Park [YNP], Wyoming, USA, personal communication, 2001) elk (Cervus elaphus) and bison (Bison bison) carcasses, and by predation on elk calves (Gunther and Renkin 1990). Grizzly bear predation on adult elk and moose (Alcesa lces) has also been reported (Schleyer 1983). However, reports of predation on adult bison are rare. In an extensive review of the historical literature on bison, Roe (1951, 1970) found only one reference documenting grizzly bear predation on bison. Review of more recent bison literature adds no additional evidence that grizzly bears prey on adult bison (Meagher 1973, 1978; Reynolds et al. 1982; Shaw and Meagher 1998). Studies of grizzly bear behavior and food habits in YNP have not documented grizzly bear predation on adult bison (Mealey 1975, Schleyer 1983, Gunther and Renkin 1990, Mattson et al. 1991, Schullery 1992, Mattson 1997, Knight et al. 1999), except for the occasional killing of severely malnourished bison in spring (Craighead et al. 1995).

Grizzly Bear Predation on a Bull Bison in Yellowstone National Park

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