Typically black bears in California's Sierra Nevada are considered relatively harmless. Yosemite National park for years encouraged campers to chase them out of their campsites, as if they were large, furry stray dogs. The legality of bear hunting in adjacent national forests encouraged bears to teach each generation of cubs to be wary of humans.The death of a bear by stoning at the hands of a boy scout troop in recent years encouraged Yosemite to retract their policy of having campers aggressively defend their campsites from bears. Expanding designation of wilderness areas has further decreased human aggression towards bears, resulting in the doubling of bear populations since the 1980s, and greater competition for food. A greater number of much bolder bears pursuing a limited food supply has resulted in an absurd numbers of vehicle and home break-ins by bears every year.
The management practices in Yosemite National Park alone have resulted in roughly 1000 vehicle break-ins by bears per year there since the late 1990s. Yosemite management focuses on the positive and notes that bear incidents are down, but as you check into campgrounds in Yosemite Valley you can still see that season's scorecard, with the numbers passing the 600 and 700 mark every Fall. Yosemite officials blame visitors, urging them to remove food from their vehicles, but even after decades of having this problem Yosemite has failed to place an adequate number of metal "bear boxes", and they've even where a few have been provided such as Curry Village, management has failed to adequately distribute them around the parking lots to encourage and facilitate their use, revealing the problem as being as much due to egregious mismanagement as anything else.
There have also been a number of attacks on humans by bears, including one last week in a campground in El Dorado County. The count was approximately a doxen from 1980-2003, but there were only 3 in the 10 years from 1983-1993, seven from 1993-1996, and with attacks in 2007, 2008 , 2009 and 2010, the rate remains troubling. Bear attacks also occur in other states such as New Mexico and Colorado, and the Sierra Club is now recommending that everyone who enters bear country carry pepper spray designed for the long distance shots needed to repel bears. Bear spray has been proven to be more effectve than guns. Protect yourself.