Bats in Pennsylvania have a huge impact on insect populations—to the benefit of farmers, foresters, and anyone who enjoys the outdoors. Yet the diminutive creatures remain widely feared, misunderstood, and unappreciated.

A Penn State professor and graduate student, doing research at a park near Altoona, are shedding some light on the mysterious nocturnal flying mammals, attempting to learn more about the calls of the state’s nine widespread bat species.

“Most people are afraid of bats, but they do us a great service, acting as an all-natural pesticide,” says Michael Gannon, an associate professor of biology at Penn State Altoona. “A single little brown bat can catch 300 to 3,000 insects per night, and a nursing mother little brown bat eats half her body weight or more each night—estimates have run as high as 4,500 insects. Colonies of 1,000 little brown bats, which wouldn’t be uncommon in the attic of a house, may eat 2,600 pounds of insects in a summer.”

Tim Blackburn, a Penn State graduate with a master’s degree in ecology, is working on his doctoral research with Gannon. Funded by the U.S. Department of Agriculture’s Forest Service and the Wild Resource Conservation Fund, Blackburn and Gannon have examined hundreds of bats and listened to more than 40,000 bat calls at more than 140 study sites in Pennsylvania and West Virginia.

The top floor of this abandoned church near Canoe Creek State Park in Blair County contains the largest known maternal colony of little brown bats east of the Mississippi River, making it a great site for bat research. The white circle shows where bats enter and exit the building.

The researchers are analyzing bat calls in hopes of using them to identify different bat species with a high degree of accuracy. Many bat calls are similar to each other and have been undistinguishable to humans.

Bats are not blind, but it is their ears that enable them to fly with such precision. Gannon points out that a bat calls up to 40
times per second, emitting a high-frequency sound. The sound waves reflect off objects such as barns and bugs back to the bat’s ears, and the animal judges where the objects are by the length of time it takes for the calls to return. Bats literally “see” with their ears, probably as well as humans see with their eyes.

“The thing you have to understand about bats,” Blackburn says, “is that there’s really no baseline data for many aspects of bat ecology. There are many questions remaining.”

Just like birds, he explains, each bat species has a unique call. To hear bat calls, scientists have devised electronic bat detectors that bring the high-frequency calls of the bats within the range of human hearing. When amplified, the calls sound like a series of clicks or chirps. Gannon and Blackburn are developing a protocol to separate and classify calls, as one might do with bird calls, to accurately identify the species.

One location for their research, the top floor of an abandoned church near Canoe Creek State Park in Blair County, is the largest known maternal colony of little brown bats east of the Mississippi River. With about 20,000 of the 3.5-inch-long bats, the colony is one of the largest in the United States.

The site is so special that the state of Pennsylvania bought the property to protect the bats with money from the Wild Resource Conservation Fund, raised from selling license plates. The church is now part of Canoe Creek State Park, and is also a research site for the Pennsylvania Game
Commission.

The bats at Canoe Creek have made their presence known to humans in a surprising way that has nothing to do with scaring residents. “Local farmers use less pesticide than other farmers growing the same amount and type of crop in other areas of the state,” Gannon says. “The bats eat millions and billions of insects over the summer.”

Wildlife scientist Margaret Brittingham, who also has done research on bats, is not surprised by the experience of farmers near Canoe Creek. “Bats can make good neighbors because they are great predators of flying insects,” she says. “They are much better than those bug zappers that so many people use.”

In addition to being critical in agricultural areas, bats are important predators of mosquitoes all through the summer in suburban areas, Brittingham points out. “That’s especially important as concerns increase about mosquito-borne diseases such as West Nile virus.”

For more information about bats, see the publication A Homeowner’s Guide to Northeastern Bats and Bat Problems. Single copies are available free of charge from your county Penn State Cooperative Extension office, from the College of Agricultural Sciences Publications Distribution Center at 814-865-6713, or on the Web at pubs.cas.psu.edu/freepubs/uh081.html.

The college’s 23-minute video, “Bat-Free Belfries: A Guide to Bat-Proofing,” demonstrates how to deal with a single bat or colony of bats in a building, and explores the role of bats in northeastern ecosystems. You can borrow the video from your county extension office. To purchase the video, contact Information and Communication Technologies—Video Unit, 119 Ag Administration Building, University Park, PA, 16802; phone 814-865-6309; fax 814-863-9877. The price is $35. Allow three weeks for delivery. Make checks payable to Penn State or include a purchase order.

—Jeff Mulhollem