By Ellen Bausback, Environmental Communicator / UF Thompson Earth Systems Institute
Published Oct. 31, 2021
Squeaky chirps filled the air as the sun set over the Florida Panther National Wildlife Refuge in March 2016. Bat researcher Elizabeth Braun de Torrez silently crouched in the underbrush of the thick pine forest, waiting for Florida bonneted bats to emerge and soar. A 24-foot tall mist net, like an oversized volleyball net, dwarfed her in the shadows, staked into the ground with poles.
The bats, a federally endangered species found only in South Florida, were to be captured when they flew into the net and became entangled. But for years the creatures had outsmarted researchers, flying up and away, over the nets.
But this time, Braun de Torrez was ready. Inspired by a tactic called acoustic luring that has been used with birds and other species of bats, the Florida Fish and Wildlife scientist came up with an idea to play recordings of bat social calls around the net sites on speakers.
“I’d hear them in flight, kind of chattering to each other, and so I thought, they’ve got to respond to these,” she said. “They just seem to be so social.”
A huge mist net surrounds a Florida bonneted bat roost in the Babcock Webb Wildlife Management Area north of Fort Myers. Courtesy of Melquidesec Gamba-Rios / Bat Conservation International.
As the sun sank beneath the horizon, Braun de Torrez switched on the speaker, and the team hunkered down, anxiously waiting for movement.
At around midnight, bonneted bats came over to investigate — and one flew right into the webbing.
“We heard it hit the net, and we cheered,” she said. “We were all very ecstatic.”
After the quick celebration, her team donned their gloves, switched on their head lamps and approached the bat to untangle it and take its measurements.
Florida bonneted bats are the largest native species of bat in the state. Image from Wikimedia Commons user Enwebb (CC BY-SA 4.0).
Using mist nets and other methods, a recent study from Braun de Torrez found that roosts, and social units, are integral to the bats’ conservation.
The species was listed as federally endangered in 2013 by the U.S. Fish and Wildlife Service. Efforts like those of Braun de Torrez and her colleagues seek to identify the bat’s ecological needs and delineate its critical habitat so that it can be protected under the Endangered Species Act.
This calls for perseverance and creative, sometimes unexpected, scientific techniques. Researchers have worked from the ground up to investigate the lives of these tiny, elusive fliers, which are thought to number at less than a thousand, far fewer than even single colonies of other species of non-endangered bats in the state.
Gotcha … Finally
Florida bonneted bats can fly high, their jet-shaped bodies built for speed and easy getaways. They eluded researchers for hundreds of hours, until the 2016 discovery that social calls attracted bats, Braun de Torrez, the terrestrial mammal research leader at Florida Fish and Wildlife Research Institute, said. Playing these chirps over speakers enticed bats to fly close enough to be captured for research.
Since this breakthrough of using social calls to attract them, mist netting — setting up tall nets that capture flying bats — has provided insights into the health and physical characteristics of the bats, allowing biologists to figure out if individuals are reproducing. They measure each captured bat’s weight and wingspan, record its sex, note if a bat is pregnant or sick and log each individual in a large database.
This also gives researchers the chance to get up close and personal with their furry subjects.
“It’s really cool, because you can hold the animal that you spend so much time working so hard to take care of,” said Melquidesec Gamba-Rios, who leads Florida bonneted bat research for Bat Conservation International. The endangered species interventions research fellow works with Zoo Miami to study how they live in urban settings.
Gamba-Rios says bigger bat species like the Florida bonneted bat aren’t as “grumpy” as their smaller counterparts. Other researchers agree.
This species of bat gets its name from the shape of its pair of ears, which resemble a bonnet. Courtesy of Melquidesec Gamba-Rios / Bat Conservation International.
“Even though they’re big and have really big teeth and jaws, they’re very docile and sweet,” Braun de Torrez said. “When you’re able to actually see them and handle them, it makes it all worth it, all the difficult parts of the job.”
The COVID-19 pandemic, however, had put a stop to bat-catching in March 2020, and the technique was only starting to be used again earlier this year.
“Number one, you don't want to harm the species, and then number two, you don't want to be creating a reservoir for the virus in wild animals again, because that's where it initially came to us from,” said U.S. Fish and Wildlife Service researcher Sandra Sneckenberger,
Poop Scoops and Pipe Dreams
Hunting for a clearer picture of the bats’ roles in their habitat can also mean getting crafty.
Bat biologists have constructed artificial bat houses — wooden boxes with open undersides — in wild research sites and in urban areas. In the field, houses allow for easy access to bats, while in the city they provide an alternative home for bats that might otherwise roost in people’s roofs.
Bats often live in artificial houses on poles, like this one located in suburban Miami. Courtesy of Melquidesec Gamba-Rios / Bat Conservation International.
To research their diet, biologists need to collect guano, also known as bat poop. Bat Conservation International researchers have come up with a simple method to do so: securing plastic “dog cones of shame” to the bottoms of the 50-foot poles that urban bat houses are attached to, Gamba-Rios said.
The poop that falls into the cones is bagged for DNA analysis and genetic testing to determine what insects the bats eat.
While there isn’t enough data yet to be conclusive, Gamba-Rios says it’s likely they eat agricultural pests, thus giving Florida farmers free pest control.
Innovations for scoping out human poop can also aid bat discoveries. To observe bat behavior, tiny cameras normally used to inspect sewers are perfect for taking a peek into the bats’ dwellings, he said.
“The beauty of science is that people think everything needs to be fancy, but no,” Gamba-Rios said. “Sometimes you just need to find the best way to collect what you need."
Still, conventional technology has proven useful for tracking down bats and determining their critical range. Biologists study foraging behavior and habitat use by keeping tabs on how often bats leave their roosts.
About as big as a grain of rice, passive integrated transponder devices are injected under bats’ skin and “ping” each time bats enter or exit bat houses with corresponding receivers. Each ping sent to the receiver contains simple information about which individual left the house and what time it left.
Tiny microchips, like the one above, are used to track bats. Image from Wikimedia Commons User Dworshak National Fisheries Complex (CC-BY-SA 4.0).
Braun de Torrez used these microchips to monitor five bat houses at Babcock Webb Wildlife Management Area, north of Fort Myers.
Because the data is a snapshot in time and doesn’t give information beyond that a bat is passing a receiver, the team assumed the first time a bat “pinged” in a night, it was likely leaving the roost. If it “pinged” again, the bat was likely returning.
A bat house that is outfitted with a passive integrated transponder reader. Image from Flickr user FWC Fish and Wildlife Research Institute (CC BY-NC-ND 2.0).
“That was the most challenging part, I think, is to come up with all of these rules so that we’re minimizing error,” Braun de Torrez said.
Using data they collected by catching each bat in the study, researchers knew whether each bat was male or female, large or small and healthy or not. They matched this profile information with the microchip time data to provide a clearer profile of each bat’s nightly behavior.
Biologists use mist nets to capture Florida bonneted bats at the Babcock Webb Wildlife Management Area. Image from Flickr user FWC Fish and Wildlife Research Institute (CC BY-NC-ND 2.0).
The team found that dominant males, the largest males of the groups, have different activity patterns from group mates and stay closer to roosts when going out, perhaps to defend them from rival males or predators. This leads scientists to believe that roosts are especially important to the species’ survival.
The males’ close-knit social behavior surprised Braun de Torrez as it is so unusual for temperate bats. Most males of other bats species are often solitary, so females and the colonies where they raise young have long been the focus of conservation instead.
“In this case, it seems that males are quite important, not just for providing sperm, but for maintaining this social structure,” she said. “It’s important to recognize that not just females are deserving of protection.”
After catching free-flying bats in nets, scientists often need to track them back to their roosts.
One way to do this consists of fitting bats with radio transmitters. This is done using collars made of nylon shoelace material and fastened with medical sutures, which disintegrate in about a month, eventually freeing bats from the devices.
Scientists go into the field on foot or in vehicles, carrying receivers which look like old-fashioned car stereos, and follow bats based on signal strength. The closer they are to the bats, the louder the ping sounds they can hear from the devices. The receivers don’t collect data, but merely guide the biologists to the bats’ homes.
Slash pine trees at the Babcock Webb Wildlife Management Area. Image from Flickr user Diana Robinson (CC-BY-NC-ND 2.0).
Sometimes they take to the skies in small planes, which eases tracking.
“It’s a lot of fun, but it can be frustrating if you don’t get a signal,” Braun de Torrez said.
Identifying roosts and knowing where they live long-term is essential to mapping out the critical habitat these bats rely on.
“It really is like a treasure hunt, trying to find the gold,” she said.
Just Grazing the Surface
Despite all their breakthroughs, scientists say they know they have a lot of work ahead of them.
Recording bat calls using microphones mounted on poles at thousands of sites throughout the region is helping scientists understand more about their distribution. Modified cameras measure the light levels in urban bat habitats and are helping researchers determine if light pollution is a threat to conservation. GPS trackers also give insight into where they live and fly.
Going forward, Braun de Torrez wants to expand behavior research to more roost sites, while Gamba-Rios’ end goal is to create a management plan for urban environments that can expand beyond Miami, as balancing conservation with development is a reality in the state going forward, he said.
The proposed critical habitat for the Florida bonneted bat is still under review. The U.S. Fish and Wildlife Service is working on addressing comments provided by the public during the public comment period.
“I feel like it [the research] has just kind of grazed the surface,” Braun de Torrez said.
To help Florida bonneted bats, people can increase awareness among their friends and family, support conservation organizations and rescue centers as well as find ways to do home repairs without disturbing or harming bats, Gamba-Rios said.
Kathy Rogers, a self-described “crazy bat lady,” said that while many of her friends freak out when they see bats, she tries to explain to them why bat species are important and should be conserved.
“I feel like we're borrowing the planet from them, not the other way around,” Rogers said.
A full moon shines over the Babcock Webb Wildlife Management Refuge, where many Florida bonneted bats roost. Image from Flickr user Diana Robinson (CC-BY-NC-ND 2.0).
The Florida bonneted bat deserves protection because it is so at risk, she said.
“We should always cheer for the underdog,” Rogers said.
People have a responsibility to protect their wild neighbors to keep the environment in balance, the bat researchers say.
“We're all part of the system here,” Sneckenberger said. “If we keep losing species, the next thing that we lose is going to be us.”
from Flickr user FWC Fish and Wildlife Research Institute (CC BY-NC-ND 2.0).
This story is part of the UF Thompson Earth Systems Institute's student-produced Earth to Florida newsletter that curates the state’s environmental news and explains what’s going on, why it matters and what we can do about it.
The University of Florida Thompson Earth Systems Institute is advancing communication and education of Earth systems science in a way that inspires Floridians to be effective stewards of our planet.