If you happen to see a bear and can't tell whether it's a black or a grizzly bear, there is a surefire way to determine which it is. Sneak around behind the bear and find a tree close by that you can climb. Creep up and slap the bear on the rump. The startled bear will initially run away from you giving you time to run climb the nearby tree before the bear turns to pursue you. If it is a black bear it will climb the tree and eat you. If it is a grizzly bear it will push the tree over and eat you.