Whether they are in your belfry or not, bats get a bad rap. Actually, up close, bats are kind of cute. They are mammals, not birds, and, according to Brown University biologist Sharon Swartz, bats make up almost a quarter of all mammal species. In fact, bats are the only mammals that can fly under their own power!
"There are bats that eat nothing but fruit, for example, and there are bats that eat nothing but insects. From the perspective of flight, these two kinds of foods couldn't be more different," says Swartz. "It's really a fundamentally different task to fly after a large, heavy, stationary piece of fruit than to fly after a tiny, highly mobile, evasive insect prey. For us as flight biologists, we're really interested in understanding how those two different kinds of bats might be designed differently."
Since 2001, Swartz has teamed up with Brown University engineer Kenny Breuer to study the mechanics of bat flight. With support from the National Science Foundation (NSF), the two scientists from very different disciplines set up a special facility, including a wind tunnel, to study bats in flight.
"We take high-speed video of bats from multiple angles," Breuer explains, pointing to a computer screen which shows a bat flying in slow motion. "We also take high-speed video of the velocity field behind the bat using a technique called particle image velocimetry or PIV, and we synchronize these two things together to measure how the wings move and the kinds of patterns the wings generate in the wake behind the bat so we can understand how bats generate their lift forces, their thrust forces; what they do in order to maneuver and to fly."
Unlike birds and insects, bats' wings are shaped like a human hand and covered with skin. So they grasp the air in flight and the skin stretches like a sail in a breeze.
"They can bend all their joints and they can move their fingers to change the shape of the wing during flight," says Breuer. "That's something birds don't have."
Swartz holds a bat in her gloved hand and spreads its wing pointing to the thin bones that connect the thin skin spanning the wing. "You can see the thumb, the second, third, forth and fifth fingers. This skin is stretchy and embedded within this skin are special muscles that allow it to use its wing in a way that would be impossible for any other flying animal."
Imagine designing aircraft with this dexterity. That's what this research could lead to and what scientists expect will happen one day. In the meantime, these two researchers will continue to study as many species as time will allow.
"I did not grow up loving bats," notes Swartz with a smile, "but for 20 years now, I've come to see the incredible beauty in their bodies, wings and faces. The more I study them, the more incredible things I learn."
With so many bat species, nearly 1,200 in all, studying each one could drive anyone batty, but not these two. Swartz and Breuer say they're perfectly happy in their bat cave!