Good news for Yosemite National Park's population of black bears: they are eating less human food thanks to new and more effective strategies from park leaders.

According to a press release, University of California - Santa Cruz (UCSC) researchers uncovered how the bears' diets have changed since Yosemite became more proactive controlling their access to human food.

Black bears are known to have a nose for human food and will break into cars, cabins and dumpsters to get it. In 1999, Yosemite implemented new strategies to keep the bears away from human food, but diet problems have yet to be completely erased.

"Yosemite has a rich history of bear management practices as a result of shifting goals over the years," study lead author Jack Hopkins, a research fellow at UCSC, said in the release. "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."

The researchers' study is published in the March edition of Frontiers in Ecology and the Environment.

Hopkins and Paul Koch, dean of physical and biological sciences at UCSC, analyzed isotopes in hair and bone samples from the bears. Hopkins said the park has used that funding to buy bear-resistant food containers, hire more staff to manage problem bears and to enhance efforts to make sure visitors do not contribute to the problem.

"This study shows the power of using museum specimens and archived historical material to reconstruct the ecology of a species and to answer pressing management questions," Koch said in the release. "The remarkable thing is that the bears that eat human food are now back to the same level of dumpster diving as in 1915, despite the fact that there are now millions of visitors in Yosemite every year and presumably a lot more garbage."

Yosemite National Park opened in 1890 and the earliest samples obtained by Hopkins and Koch were from bears killed between 1915 and 1919. In 1923, Yosemite began feeding bears where visitors could see them, as the public's interest grew.

The percentage of human food in the bears' diets rose to as high as 35 percent from 1975 to 1985. The park closed its last artificial feeding area in 1971, implemented the changes in 1991 and now the bears' human food rate is back at 13 percent from 2001 to 2007, the lowest total since 1915 to 1919.

Hopkins said the only way to stop the bears from eating human food is to stop conditioning them to eat it. Unfortunately, bears that are conditioned to eat human food will not stop looking for it until they die or are killed.

"People like to see bears, and they don't like to hear about bears being killed," Hopkins said. "But the bears they often see in visitor-use areas like Yosemite Valley are the ones that are conditioned to eat human food, and those are the ones that become problems and have to be killed."