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Vampire Bats on the Run

Vampire bats on treadmills show a surprising, distinctive running style.

Vampire bats sound pretty scary. Even though they suck blood from large mammals, however, they're remarkable creatures. They're smart. They're agile, stealthy night fliers. They have heat sensors in their noses to zero in on suitable feeding places.

Here's something else to add to the list. Scientists have recently discovered that vampire bats can run.

A vampire bat on a treadmill lopes along at 0.6 meter per second. Video-camera images taken every 24 milliseconds reveal its unusual style of running.

Researchers were surprised by the discovery. Bats are quick fliers and good at hanging upside down, but they're notoriously awkward on land. The clumsiest ones "just smack their wings against the ground and freak out," says Daniel Riskin of Cornell University. They don't take a step.

Others shuffle along, but it isn't graceful. Scientists had never before found a species of bat that can run.

Vampire bats tend to be more agile than other types of bats. They can leap from the ground into the air in any direction in just 30 milliseconds (or 30 one-thousandths of a second).

To test their running abilities, Riskin set up nets to catch bats around some cattle resting under a tree at night in Trinidad. Common vampire bats go gaga for cow blood. They're so light, though, that the cows often don't even notice, and the blood sucking doesn't harm them.

Riskin put each bat that he caught into a cage that was about the size of a two shoeboxes placed end to end. The cage had a treadmill at the bottom. When he started up the treadmill slowly, the bat began to walk.

When Riskin revved it up, he was amazed to see the animal run as fast as 1.2 meters (about 4 feet) per second. The bats pushed off from the ground with their powerful wings while they ran.

"It's not often in science that you have the eureka moment like we did," Riskin says. "I'll always remember just looking over at my coauthor John Hermanson and he looked back at me, and we just started laughing."

Most interesting of all, scientists say, is that the ancestors of vampire bats didn't run. The skill must have evolved in this species on its own.

Going Deeper

Milius, Susan. 2005. Vampires run: Bats on treadmills show high-speed gait. Science News 167(March 19):179-180. Available at http://www.sciencenews.org/articles/20050319/fob2.asp .

You can learn more about vampire bats at www.nationalgeographic.com/kids/
creature_feature/0110/vampirebats.html
(National Geographic) or bss.sfsu.edu/geog/bholzman/courses/
fall99projects/vampire.htm
(San Francisco State University).

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