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Beneficial Bats — Summer 2008 | Out Here Magazine

More than 6,000 big brown and little brown bats feed, fledge, and fly nightly from spring through fall in Tracey and Jeff Knierim’s Ohio barn and granary.

Fear-inducing 'vampire vermin' are really winged wonders

By Amber Stephens
Photography by Martin Lerman

Each May, some 6,000 bats arrive at Tracey and Jeff Knierim's Ohio barn and granary and stay through fall. And, rather than shudder at the idea, the couple embraces these tiny mammals by leading weekly bat tours so visitors can get an up-close look at the colony.

For centuries, bats have been misunderstood and maligned. Typecast as rabies carriers and vampire vermin, these communal mammals are starting to recover their reputations thanks in part to their hearty appetites.

Most bats can eat up to 2,000 insects nightly, making them nature's perfect pest control. Others, known as "flying foxes" or tropical fruit bats, are nature's pollinators. Even their guano, or manure, makes a potent fertilizer.

Eating habits vary, but the wide-ranging big brown bat — one of about 47 varieties of bats in the United States — can eat its weight in insects each night.

Naturalists estimate more than 6,000 big brown and little brown bats feed, fledge, and fly nightly, spring through fall, at the Knierims' home.

Every May, bats arrive at the Knierims' barn from their winter homes in Tennessee, Kentucky, and southern Ohio, though some bats winter as far south as Texas. By mid-June the females in this maternity colony give birth, and by July the pups are on their own. Within a month, the bats will begin their southern migration.

Bats return to the Knierims' property "because that's where they were born," but homeowners can woo a colony or a solitary male to their property with a few enticements.

Because bats "drink on the fly," their home base needs to be within 2 miles of a water source, such as a pond, swamp, or stream. Water also provides a breeding ground for mosquitoes and other insects, making them an ideal food source

Security lights and other bright night-time lights attract moths, which attract certain bats. Knierim also suggests planting evening primrose or other native foliage that moths use for food sources.

Bats also need shelter. Although many bats can roost in the smallest crevices, sleeping under shutters or even siding gaps by day, some homeowners encourage colonies by putting up bat houses.

Similar to bird houses, but with a closed top and open bottom, bat houses should be attached to a south-facing structure for a warm internal temperature. Even if bats don't roost seasonally in the bat box, some may use it as a temporary night roost or resting place for food digestion.

Place the bat box in an area away from its natural predators, which include opossums, snakes, owls, kestrels, raccoons, weasels, and bullfrogs. Once the bat house is established, be a good steward.

"The absolute No. 1 predator is humans," Knierim says. Habitat loss and destruction and vandalism of roosting caves have reduced bat populations. Even disrupting a bat's hibernation can cause dehydration or death.

Like other wildlife, bats tend to avoid humans.

"They're very sweet," Knierim says. "They stay to themselves … we love them here."

Amber Stephens is a freelance writer and and editor from Amanda, Ohio.