Wednesday, May 9, 2007

Bat researcher Cynthia Moss can barely see how swiftly her subjects slice through the air. Nor can she hear them when they speak.

That hasn’t stopped the professor from creating a body of research that clarifies just how much is known about the winged creatures. The findings are part of a bigger effort to use what is known about bats for mankind’s benefit.

Ms. Moss, director of the University of Maryland’s Neuroscience and Cognitive Science Program, has been studying how bats use echolocation to sort through the clutter around them.

Echolocation, discovered by Donald Griffin in the 1930s, helps creatures including bats, dolphins and porpoises find their way. It’s like an animal sonar in which creatures give off sonic pulses and base their movements on how the sound bounces back to them. The pulses aren’t audible to human ears, but Ms. Moss and her crew — four graduate students, three post-doctoral students and two assistants — use sensitive microphones to capture their sounds.

Ms. Moss’ research has shown, among other things, that bats have a complex way of sorting through environmental clutter to reach food. Her work also reveals that their sonic pulses are not just tied to their respiration and wing beats, but also to the information coming back to them.

Bats, despite the popular conception, aren’t universally blind, but they do use sound to get around, bathing their immediate surroundings in noise to make their way.

Ms. Moss’ bat lab features roughly 35 creatures from tropical climates. Their impromptu cave is kept at a relatively high humidity and at about 70 degrees to keep the bats comfortable.

It’s hard to see more than a dozen at a time. They hide from view in the room, with only a few flying at any one time.

Ms. Moss says one aspect of her research has revealed that many bats create a “mental map” of their environments to help them move efficiently from place to place and without hurting themselves. The bats use echolocation techniques to construct the maps, which they use not only to maneuver around obstacles, but also to find replenishable food sources.

Technology makes much of Ms. Moss’ work possible. One stark example is how she uses video cameras and computers to catch bats in flight, then slows the footage so they can be studied. To the naked eye, the flights are too quick to spot much detail.

Another lab features microphones placed along the walls to capture the bats’ vocalizations. The microphones record the sounds made by the bats, a vocabulary of high frequencies that the human ear rarely can detect.

“We can reconstruct the directional paths of bat sound,” Ms. Moss says. “It allows us to study them in a new way.”

Thomas H. Kunz, professor of biology and director of the Center for Ecology and Conservation Biology at Boston University, says bats get a bad break in popular culture.

“In Western religions, bats are considered evil, with images of evil featuring bat wings, while angels have pretty white wings,” Mr. Kunz says. “People over the centuries have associated bats with the night and darkness and fear.”

Pragmatism is changing that, he says.

“The attitude of people today is quite different,” he says, because many of the 45 bat species in the United States feast on insects. “People are recognizing the role bats play in the environment.”

Mr. Kunz has been studying agricultural regions in Texas and the role bats play within the ecosystem. Bats that feed on fruit help disperse seeds and maintain forests, while nectar-eating bats play a role in pollination for various plant species, he says.

Migration has been one of the biggest topics bat researchers have had trouble exploring.

“You tag a bat and capture it someplace else, but you don’t know when it goes or how it goes,” Mr. Kunz says.

He is working with Doppler radar technology to help understand migration patterns.

“On a clear night, we can pick up bats,” he says of the 150 or so Doppler devices around the country.

“We’ve learned something about how bats disperse from caves at night,” he says, adding that because Mexico does not use Doppler systems, his research comes to a halt at the border. “We can pick them up as they emerge in the atmosphere. Just recently, we learned we can track them to agricultural regions, whether it’s cotton or corn.”

This summer, he also will be conducting research using radio tracking devices affixed to some of the bats.

The bats’ bodies may be about the size of a human thumb and weigh about 12 grams, but the transmitters are tiny enough to have no effect on the bats’ flight plans. A suitable transmitter must be less than 5 percent of the bat’s body weight, Mr. Kunz says.

Ms. Moss and her fellow bat researchers are doing more than informing the public about a fascinating creature. Their work is beneficial to humans in a number of ways.

Allyson Walsh, director of the Lubee Bat Conservancy in Gainesville, Fla., says she is working with researchers at Brown University and the Massachusetts Institute of Technology to study bats’ flight behavior for the Air Force.

“We are looking at the flexible wings of bats [to determine] how to design flexible wings [for] aircraft for navigating urban canyons,” Ms. Walsh says. “We’re just beginning to understand the aerodynamics of having flexible wings.”

Ms. Walsh cites another project in which chemicals exuded by some bats are being studied for mosquito-repellent properties they may have. Some tropical bats exist around swarms of mosquitoes but don’t suffer from their bites, she says.

Barbara French, a science officer with Bat Conservation International in Austin, Texas, says bats have influenced technology to help the blind and soon may offer comfort for stroke sufferers.

Some canes for the blind feature echolocation-like gadgets that emit ultrasonic sounds. The pulses are translated into tones, with different tones representing different objects, Ms. French says.

Another promising bat-inspired innovation involves treatment for stroke victims. Ms. French says medical researchers are testing a solution genetically engineered to mimic the protein in vampire bats to dissolve blood clots.

“It can be administered hours after the stroke occurs. Medicines they use today are not able to do that,” Ms. French says, adding that the treatment could be on the market shortly.

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