From Outside Magazine:
“Though park staffers have had success with bear-proofing—human-bear encounters are down from a record high of 1,541 in 1998 to fewer than 200 a year—there’s been a worrisome development. Two summers ago, in a shocking turn, park staffers found that one female black bear in the Snow Creek area, northeast of Yosemite Valley, had learned how to crack open bear canisters—a veritable coup in the human-bear innovation race. She doesn’t paw or jaw the canisters into submission. Instead, she stalks a particular backcountry campsite at night, sniffing out canisters stashed near ground level, moves them to a nearby 400-foot-high ledge, then lets gravity take over. “I think she kind of rolls them,” says Lee-Roney. The bear then scrambles to the base of the cliff and retrieves the goodies. To this day, no one has seen her in action.”
http://www.outsideonline.com/2013656/yosemite-bears-keep-getting-smarter