Here is an article by Tom Stienstra from the August 30, 2015 S.F. Chronicle:
Nature bats last, goes the saying, and in the past week, clever bears in the Yosemite wilderness are getting the last word.
You know those bear-proof food canisters we’re all required to carry in our backpacks? The same canisters that have proved so effective in wilderness? So effective that many bears have left the remote wilds in order to ply the easy-to-get eats at many drive-in campgrounds in national parks?
The bears know that food is inside those canisters, you see. Drives ’em nuts, literally. If the bears stay in the wilderness, because of those canisters, they’re forced to eat plants, berries and nuts. In the past few weeks, a few bears have come up with Plan B.
In several encounters last week, bears grabbed, tossed or absconded with the bear-proof food canisters, according to rangers at Yosemite National Park. Something like a robber stealing a safe, then taking it home to figure out how to get the goodies.
Brother Rambob, on his last trip out of Tuolumne Meadows, said one hiker told him a bear grabbed his locked bear-proof canister, ran off with it, and when the hiker followed in pursuit, “the bear threw it into a deep ravine.” I heard a similar tale on a trip out of Hetch Hetchy.
Then, in separate episodes last week, reported Caitlin Lee-Roney, a wildlife specialist at Yosemite, bears went inside the tents of wilderness campers to look for food.
In another case, a hiker didn’t latch the canister quite right. Even though it was partially secured, “a bear was able to pry open the canister lid by prying it back,” said Lee-Roney.