I believe you are supposed to suspend your food up in the air, and not keep it anywhere on the ground. Bears even know how to break into cars. They have gotten so used to humans! That is so sad. I am pretty scared of Grizzly bears, but the smaller black bears are responsible for more human killings and attacks in North America. So watch out for both. Then there are the Mountain lions too.
The park does not allow visitors to suspend food from trees in the camping area. It that were allowed, there would be substantial damage to the trees given that thousands of people camp there every year. The rules in force the last time I camped there was to keep food in a sturdy locked cooler situated away from where you sleep or to lock it inside your car. I opted not to put it in our car because I've seen the damage bears can do to a vehicle while trying to get to food.