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Bats in Bay Country
By Julie Dunlap
Photos by Dr. J. Scott Attenbach

Just before sunset, dark shapes begin to dart out of a Davidsonville horse barn. First one, then three, then a dozen little brown bats spiral into the evening sky. To people who fear bats, it looks more like a scene from gothic Transylvania than from Chesapeake Bay country. But Sandra Carr, who watches the animals each evening, says, "They must have watched too many old Dracula movies."

Ancient legends and Hollywood hype have created bat phobias, says Carr, director of the Davidsonville Wildlife Sanctuary. When people see a bat, she says, "First thing they think of, it's going to bite." Yet her work as a wildlife rehabilitator has revealed bats to be gentle creatures. Most arrive at the sanctuary after car accidents, and Carr splints their delicate, leathery wings, then leaves them to recover, hanging in a dark cage. "They're just scared, like anything that comes in," she says. "Once they settle in, they just want to be left alone."

Carr's patients munch earthworms, bugs, and fruit, not the blood diet of Count Dracula fame. In fact, vampire bats live only in Central and South America, dining mostly on the blood of chickens and other livestock. And they drink only a small portion of their hosts' blood, more like a big mosquito than a deadly count. Maryland boasts ten bat species, ranging from big brown bats, with 16-inch wingspans, to eastern pipistrelles, the smallest bat in the United States. Dana Limpert, ecologist for the Maryland Department of Natural Resources (DNR), points out that all local species of bats are insect-eaters. Though each Maryland bat weighs less than one ounce, says Limpert, "they eat literally tons of insects in a summer," including corn rootworm moths, cucumber beetles, and mosquitoes. She says, "They're the primary predators of night-flying insects."

How do bats snatch insects whizzing through the air after dark? Contrary to another myth, bats are not blind. But it is their ears, not their eyes that guide bats at night. In 1938 zoologist Donald Griffin discovered that many species emit ultrasonic calls: clicks and squeaks pitched higher than humans can hear.

This sonar system, called echolocation, enables bats to detect the size, location, and movements of their prey. The hunter zones in on an insect, then uses a wing or tail membrane to sweep the morsel into its mouth. According to Limpert, bats' amazing sonar disproves the belief that the animals get tangled in women's hair: "Their echolocation can detect a human hair. You'd think they could miss a whole head of them."

The fear that all bats have rabies is also exaggerated, experts agree. Like foxes, raccoons, and other mammals, bats can contract the usually fatal disease. But according to Joe Horman, public health veterinarian for Anne Arundel County, "Less than one percent in nature is rabid." No one has died in Maryland from a rabid bat bite since 1976. Horman reassures the public that rabid bats rarely become aggressive. A sick fox or dog might attack a person, he says, but "that usually doesn't happen with bats."

But Horman also warns that rabid bats often lose their ability to fly. "Finding a bat on a flat surface raises suspicion," he says. "Don't take any chance of exposure to saliva or getting bitten. Don't handle with bare hands. If there's any doubt about exposure, put a coffee can over it, put it in a container, and call Animal Control." Be especially cautious if you find a bat in a room where someone is sleeping. Bat bites can be so slight that they do not awaken the victim. By capturing the bat for testing, says Horman, you can avoid the need to take rabies shots yourself.

Of course, it is best to keep bats out of your bedroom in the first place. A single bat may blunder into your house by mistake. It just needs an open window to escape again. But what if you discover bats roosting in your attic or shed? The bats found most often in Maryland buildings are big brown bats, little brown bats, and evening bats. Historically, says DNR's Limpert, these species roosted in large old trees throughout eastern forests. "The habitat has been destroyed," she says, "so they started roosting in houses."

October is a good time to take steps keep bats out of buildings. Young bats have left nursery colonies, and most species are migrating to winter roosts in western Maryland or other states. Limpert recommends erecting a bat box near your home as an alternative roost before you evict attic residents. Then, at dusk, go outside to watch where bats are leaving your house. Cover every exit with a one-way bat door made of hardware cloth or wire screen. The doors allow bats to get outside, but when they return from hunting, they will not be able to get back in. Excluding a colony of bats can be a time-consuming process, and Limpert recommends checking the DNR's Web site for complete instructions. The site also lists professionals you can hire to remove a colony.

Even Marylanders without unwelcome bat guests should consider mounting bat boxes, says Limpert. A properly designed and placed box not only brings efficient, natural bug control into your backyard but also helps bat conservation. In summer, a large bat box may shelter a colony of more than 100 moms and pups. Helping young bats survive is vital, says Limpert, because bats have low reproduction rates. Females of most species give birth to only one pup a year, so populations recover slowly from declines.

Scientists know less about where our bats go each fall when insects dwindle, but at least big brown bats will overwinter in bat boxes. Throughout the country, many species head for hollow trees, caves, or mines to spend the coldest months in hibernation. The ideal hibernaculum protects bats from predators and from human visitors, who might disturb the sleepers. Waking from hibernation takes so much energy that frequently startled bats may use up their fat stores and starve to death. Disturbances and closings of mines and caves are blamed for the declines of several species, including a Maryland native, the Indiana bat.

East Coast bats also face a new threat: wind power generation. Limpert reports, "The towers seem to be an attractant." Researchers have not yet deciphered why bats approach the spinning blades, but a 2004 University of Maryland study found that up to 1980 bats of six different species were killed in 6 weeks at one West Virginia site alone. Says Limpert, "With 20,000 to 30,000 wind turbines proposed for the East, they're likely to have a huge impact. We definitely need to find alternative sources of energy. But what price are you going to pay?"

Wildlife rehabilitator Sandra Carr is convinced that attitude change is the key to saving bats. Don't wait until a bat flies in your window to learn about them, she advises. Instead, go outside on a warm evening and watch them gracefully swooping across the sky. You may find bats hunting insects over your own backyard or near a street lamp in Annapolis. Carr's favorite public place to watch is Quiet Waters Park. "As the sun starts to set, you'll see them. They're pretty much everywhere."

Bats eat so many pests, says Carr, "they're worth their weight in gold." Limpert agrees, adding that Marylanders benefit from bats outside our state as well. Nectar-eating tropical bats pollinate wild and crop plants such as bananas, dates, figs, and mangoes. Fruit bats disperse seeds of rainforest trees, helping deforested areas to regenerate. Bats are not shadowy myths or movie villains, says Limpert, "They're all part of a healthy, ecological balance."

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Bat Basics

For an online field guide to Maryland's bats, bat box plans, and advice on how to cope with bats in your building, check out the Maryland Department of Natural Resources Natural Heritage Program Web site.

If a bat has been hit by a car or otherwise needs a trained wildlife rehabilitator, contact Sandra Carr, director, Davidsonville Wildlife Sanctuary, 3156 Beards Point Road, Davidsonville, MD 21035; (410) 798-0193.

If you need help capturing a bat that may have bitten or scratched a person or pet, contact Anne Arundel County Animal Control, (410) 222-8900; 411 Maxwell Frye Road, Millersville, MD 21108.

An excellent resource for information on rabies in bats and other animals is on the Web site of the Centers for Disease Control and Prevention.

To learn more about bat ecology, behavior, and conservation around the world, contact Bat Conservation International, P.O. Box 162603, Austin, TX 78716; (512) 327-9721.