Temporal niche switching by grizzly bears but not American black bears in Yellowstone National Park

Grizzly bears (Ursus arctos) exhibit temporal niche switching, adjusting their activity patterns seasonally to align with available food sources, while American black bears (Ursus americanus) maintain a consistent diurnal foraging behavior. This study, conducted in Yellowstone National Park—where human disturbance is minimal and hunting absent—revealed that grizzly bears shift peak activity from midday (spring, late summer, fall) to evening (late spring, early summer), unlike black bears whose activity remains stable around midday. Black bears do not avoid periods of grizzly bear activity, suggesting their foraging demands for lower-quality foods necessitate longer daytime foraging. The research highlights the adaptability of grizzly bears in response to seasonal food availability, contrasting with the more rigid diurnal pattern of black bears.

Fortin, J. K., Ware, J. V., Jansen, H. T., Schwartz, C. C., & Robbins, C. T. (2013). Temporal niche switching by grizzly bears but not American black bears in Yellowstone National Park. Journal of Mammalogy, 94(4), 833–844. https://doi.org/10.1644/12-mamm-a-238.1