A 15-pound cat chased a fully-grown black bear up a tree...twice!

On June 4th, an adult black bear sauntered into a New Jersey backyard, only to have met his match in an unlikely foe. That animal was none other than Jack, an orange-colored outdoor cat who, though territorial, no longer even had his front claws! Despite the bear’s immense size (up to forty times its own weight), Jack refused to back down. Oddly enough, his stubborn hissing actually scared the bear up a tree!

The cat remained at the base of the trunk for about 15 minutes and then scared the bear up ANOTHER tree when it tried to escape. Fortunately for this ‘fraidy bear, Jack was soon called into the house by his owner, which allowed the disproportionately fearful beast to flee back into the forest with everything but its pride still intact.
(source)