Yosemite Bears Reverting Back To 1915 Natural Diet, Thanks To Government Funds To Keep Bears At A Distance

By Gabrielle Jonas on March 5, 2014 3:11 PM EST

Black Bears in Yosemite Are Back to Eating Bear Food
Black Bears are relying on their own diets of grass and nuts after U.S. government officials decided to discourage bear-human interactions by limiting the bears' opportunities to eat human food. (Photo: Creative Commons)

An influx of half a million dollars to minimize contact between bears and humans in Yosemite National Park in California has succeeded in forcing black bears to revert from human to their natural diets, according to ecologist John B. Hopkins III, of Montana State University, writing in the journal, Frontiers in Ecology and the Environment. After examining the tissues of American black bears (Ursus americanus) to ascertain how much of the bears' diets consisted of human food in the past 100 years, he estimated the proportion of human food in the diets of bears in Yosemite National Park, in central-eastern California. 

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"Our goal was to understand how the foraging ecology of bears responded to changing management strategies," lead author Dr. Hopkins wrote. Using carbon and nitrogen stable isotopes to analyze the tissues of American black bears, Hopkins and his colleagues found that the proportion of human foods increased in bear diets when park personnel and visitors purposely fed bears from 1923 through 1971. But even after Yosemite officials shut down the feeding areas, human food in the bears remained relatively constistent.

It was only after the influx of a half millon dollar annual government appropriation meant to mitigate human-bear conflicts in the park from 1999 through 2007 that the amount of human food found in bears "declined drastically." As of right now, Yosemite bears consume human foods in the same proportion as they did in 1915 through 1919, meaning they're eating more grass, tree buds, nuts, fruits,  insects and the occasional deer. "This reduction in the amount of human foods in bear diets suggests that Yosemite managers have been successful in reducing the availability of human foods to bears," Hopkins wrote, adding, "This result indicates a notable management achievement in the park, considering that thousands of people visited Yosemite annually in the early 1900's while about four million people visit each year today."

Most black bears who attack humans do so out of hunger, and do it in national parks, usually near campgrounds, where the bears became dependent on human food sources, according to Stephen Herrero, author of Bear Attacks: Their Causes and Avoidance.  Twenty-three people were killed by black bears from 1900 to 1980, according to Herrero, and black bears threatened humans 1,028 times during that period, 107 of which resulted in injury, Whenever park officials closed open dumps or banned feeding the bears, black bear attacks decreased. But closing down a food source did have the opposite effect in the Liard River Hot Springs Provincial Park, in Canada, where, in 1997, a starving black bear who had been dependent on a local garbage dump food attacked and killed two people after the dump had been closed.

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