The Bats Have Come Home To Roost

Tucked in the woods off a quiet road in Sagaponack lies Sagg Swamp, a hidden gem of a preserve owned by The Nature Conservancy.

The small, 105-acre preserve sits at the southern end of the Long Pond Greenbelt system. It contains a freshwater stream that bisects a wild swamp, which visitors explore via an elevated boardwalk that winds through the heart of the wetland.

On a recent rainy Sunday at Sagg Swamp, it wasn’t the newly emerged patch of skunk cabbage or the flowing waters beneath the boardwalk that attracted notice, but, rather, a microphone and a small green box attached to a tree just off the path. A sign on the box indicated it was the property of the New York State Department of Environmental Conservation, and that it should not be disturbed.

Turns out, coming across evidence of a project like this isn’t unusual at TNC properties. As Kevin Munroe, preserve director for the Long Island Chapter of TNC, explained, research projects take place on the organization’s properties all the time.

“It’s something that has gone on throughout TNC’s history,” Munroe said. “The organization is 70 years old now, and from the very beginning, TNC has been science-based, data- and information-driven. We have partnered and coordinated with scientists from the beginning and continue to do that.”

Because TNC preserves not just land but often entire ecosystems in the midst of areas facing heavy development pressures, its properties can and do function as living laboratories for more than a dozen organizations, including research universities, the U.S. Fish and Wildlife Service, and the Peconic Estuary Program.

A call to the DEC revealed that the recording device in Sagg Swamp was placed there to detect the presence of Myotis septentrionalis, aka, the northern long-eared bat, which is listed as a threatened species both federally and in the State of New York.

Let’s face it: Bats have historically gotten a bad rap. From the Dracula legend and that old wives’ tale about bats getting tangled in people’s hair, to being the suspected source of several viruses — including COVID-19 — these misunderstood creatures of the night have been blamed for a lot of human misery.

But bats are amazing creatures that perform vital functions in the ecosystem. Not only are they voracious mosquito eaters, they are also effective pollinators.

Addie Cappello and Samantha Hoff are wildlife technicians for the DEC, and the Sagg Swamp recorder is part of a wider study they are conducting on the behaviors of the northern long-eared bat in coastal areas of the state.

The species has typically lived in places far from the shore, like upstate New York, where it roosts in caves and old mines. But in recent years, the northern long-eared bat, an insectivorous species that hibernates through the winter, has been discovered in ever-greater numbers on Long Island — especially the East End — and other coastal regions, including Nantucket and Martha’s Vineyard.

The reason for this shift is believed to be Pd or Pseudogymnoascus destructans, a fungus that grows in caves and causes what is known as white-nose syndrome in hibernating bats. Though the fungus itself isn’t believed to be harmful to the bats, it irritates them so much that it can awaken them in the midst of winter hibernation. With just enough fat reserves to survive until spring, when bats awaken early they can quickly starve to death if insects aren’t available.

“It grows in skin membranes, and it’s disturbing,” Hoff said of Pd. “But there’s some research into the mechanism that indicates what would make a bat die could have to do with dehydration.”

First spotted in a small cave in upstate New York in 2006, white-nose syndrome has spread to 33 states and several provinces in Canada. It has decimated northern long-eared bats in the Northeast, where populations are thought to have plummeted at many hibernation sites.

But while upstate populations are crashing, the bat seems to be doing quite well on Long Island — particularly here on the East End.

“We started doing our large-scale project in 2017, with a focus on summer and looking at species across Suffolk County,” explained Hoff. “We do leave some microphones out in winter as well, because we found that bats were active into late fall and we wanted to see where they were hibernating.”

Hoff and Cappello have placed microphones all over the East End, including on the North Fork, in Riverhead and in TNC’s Mashomack Preserve on Shelter Island. But they have had the best luck finding northern long-eared bats in Montauk, and, as it turns out, they have determined that they do, indeed, hibernate here.

“We thought they’d fly back to the mainland, because there are no caves or mines here, but instead we found them spending the winter in an old bunker in Montauk, or in attics, culverts and other human structures,” said Hoff. “It may be something they’ve always done.

“We have found a good number of bats hibernating on the island. The bad thing is, we had no knowledge of them before white-nose syndrome arrived,” added Hoff, who noted that the only previous study on the bats was done back in the 1970s.

Hoff believes the bats overwinter on Long Island because the coastal climate is warmer than inland upstate regions. If the bats are afflicted with white-nose syndrome, shorter hibernation periods gives the fungus less time to progress and if the bats do wake up midwinter, they stand a better chance of finding insects to eat than in colder climates.

“You have a lot more insects and a shorter hibernation,” she said. “They can stay active until November and begin activity again in late February into March.”

“It’s also possible there’s some genetic population in coastal areas vs the mainland,” added Hoff, who is currently pursuing her Ph.D. at the University of Albany with the bat study as the subject of her thesis. “I think they’ve always spent the winter on Long Island and we never knew it. This species may be more resilient and adaptable than we thought before. As the fungus continues to spread throughout the range, we are hoping our coastal bats can hang on.”

Part of the study involves actually catching northern long-eared bats and affixing them with radio transmitters so that more can be learned about their behavior and roosting spots.

“In order to determine where we’re going to try to catch, we put the detectors out first,” explained Cappello who uses two poles and a fine mist net to trap the bats. “Sam knows the hot-spots where they are and where they most likely will be caught.

“It’s similar to catching birds. We sit out for many nights and don’t catch them,” said Cappello, adding that captured bats are fitted with tiny radio trackers. “The radio trackers do fall off, and they only have a battery life of about a month. Sometimes, the battery dies before we find a hibernation site. Some bats are very feisty and will rip them off.”

To find the bats in the first place, Cappello and Hoff rely on detectors, like the one in Sagg Swamp. They have divided the island into grid cells, with each cell receiving a ranking of 1 to 5, depending on the amount of canopy cover — these bats like dense forests.

“We place three detectors per cell in three or four cells at a time,” explained Cappello. “They get left out for a specific number of nights — usually five to seven per time — and then, once we’re finished, I’ll pull off the data and move them.”

Cappello explained that though bats echolocate at a frequency higher than the human ear can hear, the detectors are able to pick up the frequencies of all sorts of bat species flying in the area.

“Each bat has a different sound shape, which is recorded on SD cards. The microphone is set to start a half hour before sunset and record until a half hour after sunrise,” said Cappello. “We can download the data and use a scanner program to look for specific frequencies. We can’t tell individual bats, but we can tell different species depending on the shape of calls and the frequency.”

She added that detectors are placed at all sorts of sites — from public lands to commercial and residential properties.

“Any of the properties we use that are not state-owned, we always ask permission,” said Cappello. “Some, like Suffolk County and New York State parks, give us research permits, and some people allow us to use their residences. Afterward, Sam makes up a report to let them know what we found. We have one Southold farmer who’s super into it,” she added.

When asked about the Sagg Swamp site, Hoff said, “That was a cool little property. I had never heard of it before. We were looking for a new spot to net; I put a detector there ahead of time and was getting a ton of activity by northerns.”

“It’s pretty small compared to others, like the state parks at Montauk, and it’s surrounded by a residential area,” she added. “We tracked a bat to a red maple tree, and he was roosting in a little crevice.

“What’s interesting is, I think you have just the right style of houses around there. Some are older, some newer, but a lot them have crawlspaces where bats could be hibernating.”

Which means it’s very possible that bats are spending their winters close by. For that reason, Hoff and Capello are always happy to find homeowners willing to let them place their equipment on their properties. Who knows … you may find that you’ve had a winter tenant all this time and didn’t even know it.

“A lot of the people we come across in our fieldwork are actually really interested in hearing about the work,” said Hoff. “On the South Fork, people enjoy hearing you have a threatened species here and it’s one of the only areas they’re surviving and doing well. They take pride in the fact that the community is supporting that.”

To learn more about the northern long-eared bat, visit https://www.dec.ny.gov/animals/106713.html. To learn more about The Nature Conservancy, visit https://www.nature.org/en-us/.