Newswise — The University of Florida faces the unique challenge of relocating hundreds of thousands of campus residents: its beloved bat colony.

The university is home to the world’s largest occupied bat houses, a trio of raised structures located on campus across from Lake Alice on Museum Road. Together, two of these houses shelter an estimated 500,000 bats — possibly the biggest bat colony east of the Mississippi River. Crowds gather regularly to watch the twilight spectacle of bats streaming from the houses to hunt insects under the cover of darkness.

Now, with the oldest and most densely occupied bat house dilapidated beyond repair, UF staff will attempt to woo its residents into the newest bat barn, which has remained devoid of bats since its construction in 2017. Staff could begin limiting bats’ access to the old house as early as mid-August, which is when this year’s bat pups will be old enough to begin flying. Then, they will dismantle and eventually reconstruct the old house.

It’s no easy task: Once settled, bats can prove very reluctant to move.

“They’re faithful to a roost,” said bat specialist Laura Seckbach Finn of Fly By Night, Inc., a nonprofit organization that works in bat conservation research, bat management and public education.

Given the size of the colony, UF scientists and Environmental Health & Safety staff are wading into largely uncharted waters. Their goals are to remove the bats before the old house collapses and prevent the colony from moving into other structures on campus. EH&S staff estimate excluding the bats will cost between $5,000 and $10,000, which the university will fund. Estimates are still being developed for repairs and reconstruction of the old bat house. Donations are being accepted at UFgive.to/BatHouse22 to fund student research on the colony and help enhance the bat houses, which are overseen by several groups on campus and belong to the UF community.

Coaxing bats into a new bat house, however, remains more of an art than a science. What makes bats choose a particular roost?

“That’s the million dollar question,” said Shelly Johnson, state specialized agent in natural resources with UF/IFAS Extension and joint faculty in the Department of Wildlife Ecology and Conservation. “UF’s bats belong to a maternity colony. Females are looking for a place that provides protection and the right conditions in which to raise their pups. That can include things like warm temperatures and ready access to food and water.”

Finn recently visited the houses to help the team of UF bat-movers, which includes Johnson, determine next steps for safely relocating the bats. After inspecting the newest bat barn, Finn said it may be empty because its plywood roosting slats are too smooth for bats to grip. The internal temperature also may be too cool for the pups.

“It's like Goldilocks and the three bears. It’s got to be just right,” Finn said.

The history of UF’s bat house

UF’s original bat house was built in 1991 as a solution to an unsightly problem – a mess of urine and guano spattering the UF Percy Beard Track and Field Stadium, then home to about 5,000 bats. When the stadium hosted the state’s track relays in the late 1980s, the bats emerged en masse to feed on the insects drawn to the bright lights. Some spectators panicked at the sight.

UF officials came up with a compromise: The bats could stay on campus, but they needed their own living quarters. The University Athletic Association funded the construction of the first bat house. Successfully relocating the colony, however, took multiple attempts, said Bradley Files, pest management coordinator for UF Environmental Health & Safety.

“We would catch thousands of bats and put them in the house,” Files recalled. “And the next day, they’d all be gone.”

As the colony grew, so did their living space. A bat barn, 20 feet from the original house, was finished in 2010, with bats moving in a year later. Another barn was built nearby in 2017. Until Finn’s recent visit, UF scientists and staff were mystified as to why bats have spurned the new barn. EH&S staff recently attached four smaller houses to the outside of the barn in hopes of enticing the bats to begin the relocation process on their own.

Now, based on Finn’s counsel, Chris Carlson, associate director of EH&S’ Facility Support Services, has drawn up a game plan to make the barn more hospitable. Possible modifications include roughening the plywood slats, adding a strip of paint with grit to help bats land smoothly, mounting landing pads and painting the barn exterior a darker color.

“Then it just takes patience,” Finn said.

Carlson said that if the bats do not move by mid-August, staff will slowly start the exclusion process at the old house and physically move bats to the newest one.

“This is more desirable than a massive one-time exclusion, which will scatter bats all over campus, leaving them vulnerable to prey,” he said.

Bats are winged wonders

While nobody wants bats in their attic — or a track stadium — bats provide important services and help maintain a balanced ecosystem. They are the primary predators of night-flying insects, offering a natural form of pest control. Scientists estimate UF’s bat colony dispatches 2.5 billion insects each night. That’s about 2,500 pounds of moths, mosquitoes, flies and beetles.

The vast majority of UF’s bats are Brazilian free-tailed bats, Tadarida brasiliensis. Brazilian free-tailed bats are one of the most common bat species in North America and the most common bats in Florida. They often make their homes under bridges and Spanish tile roofs, in attics and concrete block walls or expansion joints.

Brazilian free-tailed bats are excellent fliers and can reach speeds of up to 100 mph in level flight, according to Verity Mathis, mammals collection manager for the Florida Museum of Natural History. They are also capable of flying long distances. Their nightly forage for insects can span 30 miles, and they have been documented at altitudes of about 9,000 feet.

“The Brazilian free-tailed bat is really remarkable,” Mathis said. “When they’re migrating, they can actually show up on weather radars. This one species is just capable of so much.”

Mathis spends much of her time debunking common bat myths. Bats are not blind, and they’re not likely to get tangled in people’s hair during flight. Only three out of more than 1,400 known species of bats drink blood.

Bats are the only true flying mammals and are more closely related to humans than they are to rodents. 

“They probably get the worst rap of any mammal I can think of and it’s very undeserved,” Mathis said. “They're just trying to peacefully coexist and provide the ecosystem services that they provide.”

While very few bats have rabies, you should never handle a bat with your bare hands, Mathis said. If you spot an uninjured bat on UF’s campus, whether in a building or on the ground, contact EH&S at 352-392-1591 during normal business hours or the University Police Department 352-392-1111 afterhours.

In the meantime, don’t miss UF’s nightly bat show, which begins about 15 minutes after sunset. 

“Our bat houses are totally unique,” Mathis said. “They make Gainesville one of the best places in the U.S. to see bats.”

Listen to Mathis talk about bat facts on UF’s “From Florida” podcast. Learn how to build your own bat house, with help from UF/IFAS experts.

 

 

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Natalie van Hoose