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Black bears in Yosemite National Park and elsewhere are notorious for seeking out human food, even breaking into cars and cabins for it. Now a new study conducted by a former Montana State University graduate student reveals just how much human food has contributed to the diets of Yosemite bears over the past century.

Jack Hopkins and his collaborators estimated the proportion of human-derived food in bears' diets by analyzing chemical isotopes in hair and bone samples. The results, published in the March issue of Frontiers in Ecology and the Environment, show how bears' diets have changed over the years as the National Park Service took different approaches to managing bears and people in Yosemite.

"Yosemite has a rich history of bear management practices as a result of shifting goals over the years. What we found was that the diets of bears changed dramatically after 1999, when the park got funding to implement a proactive management strategy to keep human food off the landscape,” said Hopkins, who earned his Ph.D. in fish and wildlife biology from MSU in 2011. Hopkins is now a research fellow at the University of California, Santa Cruz. He also has postdoctoral fellowships with Peking University in Beijing, China, and the University of Alberta in Edmonton, Canada.