Vampire Bats Spread Their Wings and Run

As if it were not enough that vampire bats can swoop down from the sky to get a blood dinner from their victims, it turns out that they can also run across the ground to sneak up on them.

No other bat has been shown to run; in fact, most can barely walk, shuffling awkwardly from a sprawled position.

Daniel Riskin of Cornell University’s College of Veterinary Medicine and his colleagues made the discovery at a ranch on the Caribbean island of Trinidad, where they trapped five adult male vampire bats using cows as bait. They put the bats on a treadmill inside a cage and photographed them with a high-speed camera while the speed of the treadmill was increased.

The team was surprised to find that at higher speeds the animals broke into a full-fledged run. Their stride fulfills the definition of running, Riskin said, because all four limbs lose contact with the ground simultaneously -- just as is the case when horses run.

But the bats’ running style is unusual, the team reported in this week’s issue of the journal Nature. Most four-legged animals depend on their hind legs for most of their power. But because bats’ front limbs -- their wings -- are much more powerful than their legs, most of the propulsion comes from them.

Scientists suspect that bats, the only mammals that fly, lost the ability to run long ago. Riskin believes the vampire bats re-evolved the ability. But no one knows why. Perhaps it makes it easier for them to get out of the way when cows and other quarry kick at them, or perhaps it helps them chase smaller prey, he said.