The High Line was buzzing with activity. Different languages floated through the air as tour groups followed their guides’ colorful flags, while New Yorkers crammed their way through the throng just trying to get home early from work.
Unbeknown to the crowd, high above their heads, a different kind of activity was being recorded. That Wednesday afternoon this spring, a group of high school students had placed a small box atop a six-foot-tall PVC pipe to track the ultrasonic calls that bats use to echolocate as they fly at night.
Bats make up 20 percent of the world’s mammal species, but in New York City they’ve been a mystery to scientists for years. In the last decade, though, researchers have discovered that bats may be unexpectedly well-suited to metropolitan living, and life in the city has revealed new facets of bat behavior.
Nic Comparato, a Rutgers University Ph.D. student specializing in bats and bioacoustics, helped the high schoolers, members of the High Line Fellows program, secure the box. It was one of four ultrasonic recorders the team set up to kick off a three-year-long survey of bats on the High Line, aiming to create a map of bats in the park using a technique called passive acoustic monitoring.
Mx. Comparato, who uses they/them pronouns, said that not only are they consistently finding bat activity around the city, but also a surprising amount of it. Mx. Comparato spent last year mapping the bat population in Green-Wood Cemetery in Brooklyn and in the late summer found levels of bat activity there comparable to activity in the rural Adirondacks.
In rural areas, big brown bats hibernate in caves in the wintertime and forage in different spots during the warm season. But in cities, they tend to to act more like humans looking to settle down, sometimes finding one year-round home, a behavior uncharacteristic of this species, Mx. Comparato said.
“Bats who have to go through urban areas of migration are more strategic than we give them credit for,” Mx. Comparato said. With New York’s patchy green and concrete habitats, the bats are “like chess players” who have different moves to survive in different parts of the city.
Several species of bats call New York City home, according to a 2016 study published in the journal Urban Naturalist. They include three migratory species — the adaptable eastern red bat, which recently became internet-famous for looking like a sugarcoated jelly doughnut; the hoary bat, the city’s largest; and the silver-haired bat, known for its black fur and frosted tips. There are also two hibernators, the big brown bat, a year-round city resident, and the tricolor bat, which is almost endangered and hibernates in Dutchess County.
Like all bats, New York’s can seem elusive as they only come out to feed at dusk. During the day, they find safe places to roost, and they sleep hanging upside down in building crevices or from tree branches, sometimes mistaken as furry leaves to passers-by.
Each species appears to have its favorite city environments. Mx. Comparato was surprised to find that big brown bats dominate Green-Wood, while eastern red bats are the most common bat in all other city parks — including Prospect Park, just eight blocks away.
Finding a comfortable home in the city is one challenge for bats — finding food amid the city’s glass and steel towers is another. They have been recorded feeding on green roofs, like the one at the Javits Center, and in smaller city parks like Madison Square Park. And the eastern red bat has even been known to feed off streetlamps in McCarren Park in Brooklyn, Mx. Comparato said.
Nancy Simmons, a bat zoologist at the American Museum of Natural History who has spent most of her career deep in tropical jungles studying hundreds of the world’s 1,500 bat species, said bats are like a canary in a coal mine.
They are an indicator species that can tell us about the health of our habitat and our impact on it, Dr. Simmons said. The fact that bats have managed to coexist in New York City until now means that “if suddenly tomorrow they’re all gone, that should be a wake-up call that something has changed and it could be bad for people as well as for bats,” she said.
Bats also make being outside more pleasant for New Yorkers as they are known as nature’s pest control, consuming 20 to 50 percent of their body weight in insects every night. And they seem to be eating more than just mosquitoes. Erin McHale, another Rutgers Ph.D. candidate, found that bats had been eating spotted lanternflies since they were first detected in 2018.
The city’s human inhabitants are becoming increasingly curious about these furtive creatures. Mx. Comparato’s Urban Bat Project NYC and the nonprofit Gotham Bat Conservancy have both been leading sold-out “bat walks” in the city’s parks during the warmer months.
On a walk in May, 15 people (a majority of them birders) ambled around Indian Lake in Crotona Park in the Bronx, patiently waiting for bats in the late-spring heat.
Ivelisse Dyson, 31, learned about the walk from a queer birders group. “I like birding because it gives me another lens to see New York City,” she said. “We have actual nature here.”
She came to Crotona because seeing bats gives her a similar feeling of wonder as birding does. “I never imagined seeing them in New York City,” she said
But the bats don’t always cooperate, and after about two hours with no sightings, most of the group headed home.
Then suddenly, there was a flash of movement in front of a street lamp: It was an eastern red bat flying in wide loops around a tree — its translucent wings in constant motion. The bat emitted a faint ruddy glow every time it passed the light. The few people who stayed fell mostly silent, punctuating each looping pass with a gasp.
While New York City bats have to contend with the challenges of urban living, the city might also be a safe haven for them. For the past 20 years, bat populations in the northeast have been decimated by a deadly disease called white-nose syndrome that was discovered in 2006 in a cave near Albany. It has caused millions of bat deaths and killed up to 99 percent of different hibernating species, explained Winifred Frick, the chief scientist of Bat Conservation International.
As researchers race to curb the disease, they are finding that certain bats that live in urban areas and hibernate in human structures may actually be less affected by white-nose syndrome than their rural counterparts who hibernate in infected caves and mines.
There is optimism and irony in the fact that “some species benefit from human activities,” said Dr. Simmons. “While we may be destroying parts of their habitat, we may also be, without knowing it, providing refuge.”
There is still so much more to know about these nocturnal city neighbors. As the research continues, scientists are acutely aware of the effect that climate change is having on bats. It’s possible that warmer temperatures in the northeast may soon lead to a new resident bat.
In a study published last month in the journal American Museum Novitates, Angelo Soto-Centeno, an assistant curator at the American Museum of Natural History, found Brazilian free-tailed bats, a subtropical species, thriving in New Jersey — the farthest north they’ve been recorded on the East Coast of the United States. Dr. Soto-Centeno said it was likely only a matter of time before this bat, too, will cross the Hudson River and make New York City its home.
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