As dusk settled over Gainesville on a November night, a handful of people gathered behind fences enclosing an open field on Museum Road, waiting.
Bundled in blankets, they stood with their eyes glued to two bat houses in the field, searching the dark sky for bats and expecting a show that has become a popular Gainesville must-see. But the show they got was perhaps not what they had hoped for, as hundreds of bats have disappeared from the houses, leaving experts, biologists and bat fans wondering where they went.
Mainly two types of bat species — the Brazilian free-tailed bat and the evening bat—have resided on UF’s campus since 1991 when the first bat house was built. They’re migratory species, meaning their populations can fluctuate throughout the year. But after a routine inspection, UF Environmental Health and Safety was concerned that the numbers were lower than normal.
They attributed the population dip to potential behavioral changes due to the back-to-back hurricanes in September and October or a predatory threat.
Brad Files, the pest management coordinator for Environmental Health and Safety, was a part of the team that inspected the bat houses. He said the numbers he saw were alarming.
“They’re missing and we don’t know exactly why,” he said. “It was kind of shocking that that had occurred.”
Files said he assumed the storms had something to do with their departure. He also said some bats have been found in other areas of campus where they had not been before, but it remains unclear as to where all the bats went.
“We got a lot of wildlife biologists scratching their heads trying to figure it out too,” he said. “We’re just waiting for them to see if they’re going to come back and how quick they’re going to come back.”
Associate Director of Environmental Health and Safety Chris Carlson said the bats are typically very loyal to their roosts and are beginning to return in small numbers. He also said the hurricane could be to blame for their abandonment, but noted the houses did not sustain any damage from the storms.
“The houses are still in very good shape,” he said. “Now that they’re coming back, we’re continually monitoring them on a regular basis to make sure that bat population is increasing to where it should be.”
Carlson said Environmental Health and Safety has been consulting with field experts to maintain the bat houses and ensure that they remain a good place for the bats to live.
“We do like to keep them around,” he said. “They’re kind of iconic for our campus.”
One of these bat experts is Shelly Johnson, a state specialized agent in natural resources with UF’s Institute of Food and Agricultural Sciences and affiliate faculty member in the Department of Wildlife Ecology and Conservation at UF.
Johnson said it’s normal for the bat colony residing in UF’s bat houses to shrink during the fall and winter months. The bats are part of a maternity colony, she said, so the population is naturally larger in the summer after they’ve had their pups.
In the summer, the people who come to watch the bats leave the houses in a nightly event, known as emergence, might see up to half a million bats, but numbers decrease once the pups become independent and disperse.
However, Johnson said the current bat population seemed to be lower than usual.
“It’s not unusual for there to be fewer bats…but it does seem like [the population] dropped more than it normally would compared to previous years,” she said. “Maybe something a bit more unusual is going on.”
She said the cooler temperatures caused by the hurricane could have changed the bats’ behavior. Bats are less likely to forage for food when it’s cold, and the sudden drop in temperature after the hurricane could have affected the bats' desire to stay, according to Johnson.
“Hurricanes and change in temperature created an unusual behavior where they disperse more than they normally would. And it doesn't mean that they won't come back,” Johnson said. “They’re probably dispersing in a way that might not be obvious where they're going because they're going in very small numbers.”
But even when bats follow normal migration patterns, experts don’t know where they go. Bats participate in “seasonal mini migrations,” in which they breed in other locations and come back to the roost to have their pups, according to Shari Blissett-Clark, president of the Florida Bat Conservatory.
“We really don't know where they go. Off to some moonlit glade somewhere, and they have a big party, I guess. I don't know,” she said. “But oftentimes, the breeding season is interrupted by late-season hurricanes, which is the case this year. So, we believe that the storms have extended the breeding period.”
Blissett-Clark said besides hurricanes, rising temperatures and climate change has also created problems; bats are beginning to have pups sooner and their behavior is beginning to shift, she said. She and others are trying to mitigate the impacts of the summer heat so the flying mammals can continue to provide services vital to the ecosystem and human health.
“[Bats] are responsible for more insect control and more insect population balancing than anything else in the world,” Blissett-Clark said. “Bats in Florida consume anywhere from 2,000 to 4,000 or 5,000 insects a night, depending on the species. The very fact of the matter is that bats consume mosquitoes every single night, and so indirectly they're helping to protect our health.”
Jacqueline Belwood worked on the first bat house as a graduate student in UF’s entomology department. She said bats are a “huge resource” on campus, and the insect control and fertilizer they provide benefits UF’s food pantry as well as local farmers.
Belwood said she wished bats were the subject of more research considering their importance to humanity.
“There's such a conspicuous presence on the University of Florida campus, but in reality, we know very, very, very little about them,” she said. “We don't know where these animals are going to feed. We don't know what they're feeding on.”
Belwood said she’s beginning to investigate these questions using Doppler radar, a type of weather-tracking tool, to figure out where the bats are going. She also said she plans on collecting fecal matter from the bat houses and applying molecular techniques to determine the DNA of the insects they’re consuming to better understand bat behavior and their impact on agriculture.
She said research won’t start until the spring or summer.
Until then, the bats’ whereabouts remain a mystery. The bat houses will undergo maintenance during this population lull, but Environmental Health and Services could not specify a starting date.
The bat houses will continue to welcome visitors to watch the bats emerge every night. Bats usually emerge 15 to 20 minutes after sunset, according to the Florida Museum of Natural History.
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