Late season frosts and changing snowpack may exacerbate human–bear conflicts

Abstract

The North American black bear (Ursus americanus) is an opportunistic omnivore that depends on seasonal availability of fruits, nuts, grasses, and forbs for survival. Black bears on the urban–wildland interface also use anthropogenic food resources, especially when natural food resources are scarce. Consequently, natural food failure can exacerbate human–bear conflict, resulting in increases in human-caused mortality via vehicle strikes and management removal. Climate change is expected to increase the frequency and severity of extreme weather events, including drought or late frost. These climatic events may affect the spring growth resulting in loss of natural foods for bears and lead to heightened human–bear conflict in the future. In this study, we examined the effects of weather (snowpack and final freeze dates) on natural survival and cause-specific mortality (management removal and vehicle collision) of black bears in northwestern Nevada, using an extensive capture–recapture database (509 bears captured between 1998 and 2022). Our results indicated that late freeze dates were associated with a higher probability of conflict, increased probability of management removal, and reduced natural survival. Snowpack (snow-water equivalent) was weakly correlated with the probability of management removal, but the association was much weaker than the effect of late freeze dates. Anticipating the effects of late frost and snowpack on human–black bear conflict will help managers better anticipate and respond to potential high-conflict events.