Giselle Hosein peers into the dark sky above a manicured fairway on the Coral Gables Granada Golf Course, trying hard to see what she can so far only hear: an elusive Florida bonneted bat, among the rarest in the world.
“It took me three or four months before I was actually able to see one,” she said.
The bats, which number fewer than a thousand, have found an unlikely foraging ground at the nine-hole course. By day, the former orchard draws mostly duffers and retirees, or joggers cruising the perimeter past ritzy villas and condos — lawyer Roy Black and wife Lea, of Real Housewives fame, live in one walled compound. Former Gov. Jeb Bush once occupied a condo. But at night, the bats come out to play, feasting on insects to a steady rhythm of trills and tweets.
“When it gets dark, you hear them right next to you, but you can’t see them,” said Hosein, a research assistant to a Florida International University biologist and bat expert. “It’s like your mind is playing tricks on you.”
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Then she sees it: a dark outline soaring against white clouds dotting the midnight blue sky. Just as quickly, the bat vanishes. Yet its calls — constant chirps to get its bearings mingled with chatter that could signal mates, pups or predators — fill the muggy night like a mockingbird on fast forward. Over the next hour, Hosein spots more bats, or the same one, a dozen times. A sound meter tucked into a ficus tree on the course typically records a thousand calls each night.
The bats, which have the smallest range of any bat species in the western hemisphere, are one of the New World’s most vulnerable, found mostly around South Florida. In November, U.S. wildlife managers added them to the endangered species list, citing both habitat loss and annual mosquito-spraying as critical threats.
The government and biologists are now trying to determine where the bats live and whether their habitat can be protected. But the bats aren’t cooperating.
“We literally know nothing about them. We know they have a low reproduction rate, but we don’t know how fast ... or what they’re eating, so we don’t know what to protect,” said Dr. Frank Ridgley, head of conservation and research at Zoo Miami. “Until we answer those questions, it’s hard to get a recovery plan.”
Despite years of study, finding natural roosts has been difficult, making it hard for scientists to scrutinize how they live. Until last year, no roosts had been found since the 1970s. The single roost — discovered by a biologist looking for woodpeckers in tree holes at the Avon Park Air Force Base in Central Florida — contained a single bat.
“We’re still finding out what we do know and what we don’t know. We haven’t listened everywhere and we might find it somewhere else,” said Dana Hartley, supervisor of the endangered species program for the U.S. Fish and Wildlife Service, which plans on releasing a draft proposal addressing potential habitat on Sept. 30.
The bats — officially Eumops floridanus or Eumops for short — show up most frequently at the golf course and sometimes near Zoo Miami. Biologists think the fuzzy bats, with ears so round they form a brim-like bonnet, historically roosted in pine rocklands and wetlands that development shrunk over the years.
A colony also roosts in several man-made bat houses in Punta Gorda and Fort Myers. Last year, two trained dogs from Auburn University spent 21 days hunting for roosts in South Florida, but only turned up a single rice-sized bit of scat that a trainer keeps frozen, hoping to find a lab that can accurately test its DNA.
Eumops also tend to be sneaky. While other bats form massive colonies, leaving roosts in noisy, thundering herds, the hamster-sized Eumops may live in small, restless harems that attach to a single male and frequently change roosts.
Scientists rely primarily on audio equipment to track bats because they are so hard to see. Nets can catch some bats, but only those that fly low. Eumops tend to cruise at about 30 feet. And some bats fly even higher. In Texas, a team following a related species attached bat detectors to a weather balloon to track colonies feeding on clouds of moths traveling at about 3,000 feet, said Cyndi Marks, who founded the Tampa-based Florida Bat Conservancy with her husband, George, in 1994.
But until the 1990s, when digital technology allowed researchers to capture the densely packed short sound waves emitted by the bats, scientists didn’t have equipment sophisticated enough to record Eumops, she said.
“Suddenly we had this new equipment that could not only record, but record on a memory card. So then we could plug the card into our computers and determine the species,” Marks said.
The first Eumops was found in Miami in 1936. A spotty chronology followed: a limestone outcropping near the University of Miami housed a colony in the 1960s. In 1979, the first West Coast colony was found in a wildlife management area in Punta Gorda. In 2000, a survey in the Ten Thousand Islands picked up four calls. After a skull was found in the Fakahatchee Strand, Marks managed to record some calls near a camp site. The longest-monitored colony lives in three backyard bat houses erected in Lee County in 2003.
The most reliable colony, and the one that provides the most evidence for study as well as the scat needed to train the search dogs, occupies about five roosts the state erected on the Punta Gorda wildlife land starting in 2007.
“But we really want to find natural colonies,” said Marks, who helped with the 2013 search efforts across Miami-Dade County and who, despite years of recording, has never heard the bats without a bat detector, a device that translates their calls for human ears.
“Younger people can find them,” said Marks, who is 60 and was surprised to find they could be heard so easily on the Granada golf course.
Eumops are one of the few bats that can be heard, said Kirsten “Kisi” Bohn, the FIU biologist whose work on bat songs is featured in the current Science magazine. But it depends on your ears. Women tend to hear higher frequencies than men — an evolutionary quirk that makes women more attuned to a baby’s cries, she said.
After federal wildlife managers agreed to speed up their endangered status review of the bat in 2011, the race to study Eumops was on. And that’s when the bat-detecting dogs entered the picture.
“I did not have very good expectations,” said Bart Rogers, Auburn’s Eco Dogs trainer, who taught his two labs, Felix and Baxter, to hone in on guano from the Punta Gorda bat houses.
Rogers worried that the guano, shipped frozen, would not accurately reflect scat in the wild. Sure enough, the dogs found guano, but were never able to sniff out Eumops specifically. The closest they came to a Eumops was a single, grain-sized piece of scat at the bottom of tree in Punta Gorda, where researchers saw a large bat, presumably Eumops, flying away, he said.
“The dogs don’t lie, so we probably found an actual roost site. We just have no way of confirming it,” said Rogers, who scooped up the guano and has kept it frozen ever since.
As luck would have it, Bohn, the FIU biologist, had moved to a house three blocks from the Granada Golf Course in December 2012. The second night, as she sat in her backyard drinking a glass of wine, she heard a familiar sound.
“I went, ‘Holy crap, that’s a bat,’ ” she said.
Once her equipment arrived at the new house, Bohn verified what her ears were telling her.
“As soon as I got my equipment, I went crazy. They’re all over the place,” she said.
Bohn, who was drawn to bats because she was interested in studying communication in mammals, is now trying to coordinate additional research on the golf course bats. FIU provided some start-up funds, allowing her to buy three additional song meters at $3,000 each. She and Hosein, who expects to graduate this summer, have so far put up two in trees on the course. And she’s working with a London biologist doing DNA analysis on what the bats eat, which will help determine their habitat. But she needs help.
“We know they roost in groups of four to 10, maybe 20. But that’s a small group and you have to be in the right spot at the right time to see them coming out of their roosting. It’s elusive,” she said.
Bohn has toyed with the idea of holding a bat night, in which volunteers armed with iPhones or iPads using an app called SpectrumView could be posted around the golf course to help locate the bats at dusk to pinpoint their roosts. In the meantime, she’s asking for volunteers through her website, http://kisibohn.com/Kisi/Eumops_floridanus.html.
“I don’t know what they’re doing yet, but they’re basically talking to each other. They’re not just echolocating, but they’re communicating to each other while they fly,” she said. “We would learn a ton more if we could find their roost sites.”