Aspects of Evolution and Adaptation in American Black Bears (Ursus americanus Pallas) and Brown and Grizzly Bears (U. arctos Linne.) of North America

Certain behavioural, ecological, morphological, and physiological differences between grizzly/brown bears and black bears a re related to the different habitats favored by each species. It is suggested that care of black bear cubs and hence reproductive success for black bears is tied to the forest biome, and that the grizzly/brown bear in branching out from the forest onto non-treed a reas such a s tundra, grasslands and prairie edges, gained rich new food sources, but also became more aggressive than the black bear, a behavioural adaptation to cub care in this new habitat.