Black bear.

Black bear sends visitors fleeing in Yellowstone.  Image by Todd Ryburn / CC BY 2.0

Visitors to Yellowstone National Park were sent scrambling when a sow charged them for coming too close to her cubs. A video of the incident shows camera-toting tourists running for safety as a female black bear gives chase. Black bears are not usually aggressive, but they have been known to become protective if they sense that their cubs are in danger. A parks spokesperson said visitors to national parks should remain as far away from bears as possible, especially during the spring when cubs are young. Read more: