Now, a new study shows their efforts have paid off, and that bears in the park are eating less and less human food.
"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," Jack Hopkins told Live Science. "This suggests that the bear's diets are likely going back to their natural diet."
Hopkins, a wildlife ecologist at the University of California, Santa Cruz, is the lead of author of the study which used hair samples to track the diets of some 200 bears in the park. Scientists were able to test hair samples for chemical signatures of human and wild food sources, and analysis showed that since the park enacted more stringent food storage requirements, consumption of human food by park bears is down 63 percent.
The details of the study were published in the March issue of the journal Frontiers in Ecology and the Environment.
The progress evidenced by the new study is a quite a turnaround. Between 1923 and 1971, Yosemite actually maintained several feeding areas, to attract bears for park visitors to see.
Previous research by Hopkins and his colleagues has shown that bears are conditioned early on to have a taste for human food. Once a picnic basket snatcher, always a picnic basket snatcher, scientists say of nosy black bears. That's why prevention is key. Stop the bear's first taste of human goodies from ever happening, and you prevent a lifetime of snooping through campsite debris.