Are black bears a factor in the restoration of North American grizzly bear populations?

Abstract

Abstract We assess the potential for American black bears (Ursus americanus) to limit the growth of colonizing or severely reduced grizzly bear (Ursus arctos) populations. Managers are faced with the challenge of increasing the size of small (N < 75) grizzly bear populations in the North Cascade, Selkirk, Cabinet–Yaak, and Bitterroot recovery areas of the USA and Canada. These populations are mainly limited by human-caused mortality. However, other factors such as competition from black bears could impose additional constraints. Brown and grizzly bears and American black bears evolved separately until about 13,000 years ago and, as a probable consequence, they can have substantial diet overlap. Where meat and roots are available, grizzly bears consume more of these foods than do black bears. Where fleshy fruits and succulent forbs are the primary high quality bear foods, as in the North Cascade, Selkirk, and Cabinet–Yaak ecosystems, dietary overlap between grizzly and black bears can be almost complete. L...