Dietary adjustability of grizzly bears and American black bears in Yellowstone National Park

Grizzly bears and American black bears in Yellowstone National Park exhibit dietary adjustability, with male grizzly bears showing a decline in meat consumption over 30 years. The study estimated diets using stable isotope analysis of hair samples and GPS-collared bear data, revealing that while female grizzly bears maintained consistent meat intake, male grizzly bears reduced their reliance on animal matter. Cutthroat trout consumption dropped by 70% in grizzly bears and 95% in black bears between 1997–2000 and 2007–2009. Elk remained a primary prey, while whitebark pine nuts were replaced by false-truffles when scarce. This adaptability highlights the resilience of both bear species to changing resource availability.

Fortin, J. K., Schwartz, C. C., Gunther, K. A., Teisberg, J. E., Haroldson, M. A., Evans, M. A., & Robbins, C. T. (2012). Dietary adjustability of grizzly bears and American black bears in Yellowstone National Park. The Journal of Wildlife Management, 77(2), 270–281. Portico. https://doi.org/10.1002/jwmg.483