Effects of Food Supply, Predation, Cannibalism, Parasites, and Other Health Problems on Black Bear Populations

Effects of gunshot and human settlement on black bear numbers and range are well documented, but effects of natural factors are less well known. In this paper, effects of food supply, predation, cannibalism, and health problems on black bear populations are evaluated using information in the literature and data obtained in Minnesota during 1969-1978 from 119 radiocollared black bears and their cubs. Supplies of fruit and mast vary greatly among regions and from year to year. Available evidence indicates that availability of these easily digestible, energy-rich foods is the most important factor influencing growth rate, age of first reproduction, and intervals between litters in black bears. Survival of cubs and yearlings also varies with food supply, but predation also may be a significant factor in cub survival. The extent to which cubs are killed by larger bears, wolves, and other predators is an important area of bear biology requiring further study. Predation on yearlings and older bears appears to be too rare, according to available data, to significantly influence population dynamics, but there is evidence that habitat utilization by black bears may be limited in some areas by grizzly bears. Little information is available on causes of natural mortality among dispersing bears. A variety of health problems have been reported for black bears, but no serious pathological condition has been found to be common and no case of population decimation due to parasites or disease has been reported. The most commonly reported