SSS 2010-12-03（在线收听）

They’re everyone’s worst nightmare when it comes to swimming in the ocean: great white sharks. That’s despite the fact that the number of fatal shark attacks annually can usually be counted on the fingers of one still attached hand. But a new study finds that until great whites get at least three meters long, they’re less and more. Because a full-force bite could wind up hurting them.

In research published in the Journal of Biomechanics, scientists used 3-D computers models and advanced engineering techniques to study how sharks hunt and kill their food.

Great whites have jaws and teeth that are perfect for a powerful chomp on prey ranging from small fish to large marine mammals. But the researchers were surprised to find that a shark less than three meters long only looks like it could manage that killer bite. Because it has not developed enough stiff, mineralized cartilage yet. A bite that would be lethal to a large marine mammal could damage the shark’s jaws.

The finding may explain why the few shark attacks that do happen on people are rarely fatal—until it’s pretty big, the great white’s reputation is worse than its bite.

Thanks for the minute. For Scientific American’s 60-Second Science. I'm Cynthia Graber.