Backyard bat houses promote pest control, says UF expert

October 29, 2001

GAINESVILLE, Fla. — Forget the garlic and put away those wooden stakes.

If you’re seeing more bats this Halloween, it’s probably because homeowners are installing backyard bat houses to encourage the flying mammals to hang around and provide natural pest control, says a University of Florida expert.

“A few dozen bats can make a big difference in a neighborhood,” said Mark Hostetler, extension wildlife specialist with UF’s Institute of Food and Agricultural Sciences. “Many species can eat 1,000 flying insects per night, including mosquitoes, moths, flies — anything they can catch.”

Hostetler said interest in backyard bat houses has increased among Florida homeowners since July, when mosquitoes carrying West Nile virus were first detected in the state. The virus can cause severe encephalitis in humans and is occasionally fatal. It was first documented in the United States in New York in 1999.

“Some bat house inquiries we get now are from people concerned about West Nile,” he said. “I tell them there are no guarantees a bat house will reduce their risk, but it can’t hurt.”

Bat houses provide shelter during daylight hours when bats are inactive, he said. Shaped like suitcases, the houses typically are made of wood and placed high atop poles or buildings. Inside, bats hang vertically from the walls, crowded together to share body heat.

“Not all bat species will use a bat house, just the social ones,” Hostetler said. “In the U.S. Southeast you’re most likely to attract Brazilian free-tailed bats, Southeastern bats and evening bats. Because bats are peaceful creatures, multiple species will sometimes share the same house.”

Installing a bat house will encourage the animals to remain in the neighborhood, he said.

According to Bat Conservation International in Austin, Texas, thousands of bat houses currently are used in the United States and abroad, but no exact figures are available. The first known bat house was built in San Antonio, Texas, in 1902. Small backyard bat houses became popular in Europe in the 1960s and have been catching on in the United States since the mid-1980s.

Gainesville veterinarian Debbie Kemmerer has about 600 free-tailed and evening bats in a bat house above her office parking lot. She said bat houses can help educate the public and dispel myths about the winged creatures.

Bats don’t land in people’s hair, and the incidence of rabies in bats is extremely low, she said. While bat houses pose no health threat to humans or pets, children should be instructed to steer clear of any bats they find on the ground.

“If you’re able to approach a bat, it’s injured or sick,” she said. “Don’t handle it. Instead, call animal control and leave the job to a professional.”

She said bats are not rodents, though they are mammals, accounting for more than 900 of the world’s 4,000 mammal species. Bat populations are declining worldwide, often due to loss of habitat.

“In residential areas, bats often have few places to roost and some options may be inconvenient for homeowners, such as attics and sheds,” she said. “By installing bat houses and simultaneously blocking access to places where bats aren’t wanted, homeowners can have the best of both worlds.”

Kemmerer said UF’s bat house is an example of good bat management. When a large colony of Brazilian free-tailed bats roosting in a campus stadium caused odor problems, university officials installed the massive house, which now holds about 100,000 bats and has become a local landmark.

Bat houses don’t need to be large to be beneficial, said Mark Kiser, coordinator for the North American Bat House Research Project, part of Bat Conservation International. BCI recommends that homeowners install bat houses that can accommodate 100 to 300 animals.

“Our understanding of good bat house design and placement has improved dramatically in the last few years,” Kiser said. “Bats have specific requirements for things like landing area, warmth, ventilation and space.”

He said BCI is one of several organizations that provide free bat house plans online. The BCI Web site is located at www.batcon.org.

To encourage commercial bat house manufacturers to design products and instructions that conform to bat needs, BCI operates a certification program. Recommended bat house brands and models are listed on the organization’s Web site, along with certification criteria.

“Unfortunately, many manufacturers use old designs that are flawed in some way,” he said. “This is a developing industry, and the best bat houses are made by people who keep up with the research.”