Getting a grasp on Vermont's furtive, fly-by-night creatures
As I trudge up the steep, Mars-like terrain of Copperas Hill on the outskirts of South Strafford, it dawns on me why this is called Orange County. The landscape is rust-colored and barren, and it bears the unmistakable scars of industrial plunder. At the crest of the hill, a huge auburn gash is pocked with two yawning caverns. This is the north cut of the Elizabeth Mine, an abandoned copper adit dating back to 1809 that's now a federal Superfund site. I've come here with a group of wildlife biologists who will spend the evening studying some of Vermont's most poorly understood and much-maligned creatures: bats.
Standing at the lip of the deep, narrow gorge is Scott Darling, a wildlife biologist with the Vermont Fish and Wildlife Department. Darling is setting up a "harp trap" -- a 6-by-8-foot rectangular contraption composed of two rows of fishing line strung vertically and spaced several inches apart, like the strings on a harp. At its base is a clear plastic pouch for catching bats as they fly into the net. At nightfall, two of these traps will be positioned in the bats' likely flight path, about 30 yards from the mine's entrance. It's a harmless and effective tool for studying these nocturnal critters up close.
And there's still much to learn about them. Bats are a relatively new area of focus for the Fish and Wildlife Department, which only three years ago began designating significant funds to their study. While wildlife biologists know a lot about large mammals such as black bears, coyotes and whitetail deer, they remain surprisingly in the dark about the habits of Vermont's nine bat species -- where they roost, how far they migrate, where they're distributed around the state and whether their numbers are holding steady or, like other bat populations around the world, declining.
Bats are considered an indicator species regarding the health of forests, riparian areas and invertebrate populations, Darling explains. Like frogs and other amphibians, they can reveal a lot about the long-term impacts of human development, habitat fragmentation and environmental toxins. But first, scientists need to establish a good baseline of data, something that's not been done yet.
Vermont is home to 25 identified bat roosting spots, called hiburnacula, some of which haven't been surveyed in decades. Fish and Wildlife only learned of this site, Elizabeth Mine, two years ago. Darling suspects, however, that it's one of the state's most important bat hangouts, in terms of the number of individual bats and the variety of species. This is an ideal time to gather data, since it's the start of the fall swarming season, when bats migrate to the cave to breed.
As the light fades, Darling calls the group together. It includes Bill Kilpatrick, a biology professor from the University of Vermont; Tony Tur, an endangered species biologist with the U.S. Fish and Wildlife Service; Kim Hall, a former Vermont Fish and Wildlife employee who now lives in Colorado; and Kristen Watrous, a UVM graduate student.
Tonight's work has two goals, Darling explains: First, he wants to determine whether Elizabeth Mine is home to either the Eastern Small-footed bat (Myotis leibii), a species that is threatened in the state, or its rarer cousin, the Indiana bat (Myotis sodalis), which is endangered nationwide. It's an indication of how little is known about local bat populations; as recently as 2000, wildlife experts didn't even know Indiana bats lived in Vermont. Two years later, they discovered 2500 to 3500 of them in the Champlain Valley alone, including 270 living in a huge, dead, white pine in Middlebury.
Darling's second goal is to get some sense of the total number of bats that use Elizabeth Mine. On a warm summer night two years ago, volunteers here trapped about 600 bats in two hours. That number is comparable to the number of bats caught at the entrance to Dorset Cave on Mt. Aeolus in southern Vermont. Dorset Cave is the largest known hibernaculum in the state, home to at least 23,000 bats. In parts of that cave, the walls and ceilings are completely covered with dense bat colonies. "It's a pretty cool place if you like bats," Darling notes, "and pretty horrific if you don't."
Vermont's bat populations pale in comparison to those found in the West. Austin, Texas, for example, is home to one of the world's largest urban bat colony. Each night at dusk between March and mid-November, 1.5 million Mexican free-tailed bats emerge from under the Congress Avenue Bridge. When the bridge was built in 1980, the long, shallow crevices beneath its span inadvertently created a perfect roosting habitat for the migratory mammals.
Though the nightly swarm of bats at the entrance of Elizabeth Mine isn't nearly that dramatic, this site is fascinating for other reasons, Darling says. The mine, which yielded 102 million pounds of copper before it was abandoned in 1958, is 975 feet deep, 10,000 feet long and contains approximately five miles of underground passageways. But the mine is also treacherous to explore, and in recent decades has only been accessed by experienced cavers, not wildlife biologists. How many bats live inside is anyone's guess, Darling says.
Luckily, we have near-perfect trapping conditions for getting an idea. The evening is clear, warm and calm, with no moon. Most local species of bats weigh between 4 and 8 grams each -- about the same as a few pennies -- so they don't do well in wind or rain. They also prefer the cover of full darkness, which protects them from predators such as owls, explains Darling. From across the valley, we can already hear the distinctive "Who cooks for you?" call of a barred owl. The lack of moonlight is beneficial for another reason: It makes the harp traps less visible to the bats. Contrary to popular myth, bats see quite well, even in the dark.
By 8 p.m., the two harps are positioned along a path at the edge of the gorge, some distance from the mine's entrance. Darling explains that bats tend to follow natural and manmade corridors through the woods -- streams, hiking trails, logging roads -- so it's unnecessary to set up the traps right at the mouth of the mine. As if on cue, Hall announces that she's already caught one.
Donning a headlamp, I hurry to the trap, where Hall pulls a small, cheeping animal the size of her thumb from the plastic pouch. Instinctively, the mousy-looking creature bares its tiny, sharp teeth. But there's little risk of injury -- unless it's rabid, which is rare -- since a bat's teeth can barely break your skin. Nevertheless, all bat researchers are vaccinated for rabies. And contrary to another popular misconception, bats don't drink blood; at least, no species in North America do. They use their razor-sharp teeth for crunching through the exoskeletons of insects.
"Hi, there, little fella," Hall says, holding the bat in the palm of her hand. She fans out its wings and shines a flashlight from below through the thin membrane to study its wing joints. A bat's wings, which are structurally equivalent to other mammals' hands or paws, can reveal its age. Certain bones in a young bat's wings aren't fused yet, Hall explains, like those in the skull of a human infant.
These scientists care about the bats' age because, unlike rodents, bats don't produce large litters that die young. In fact, each year a female bat gives birth to just one pup, which can live as long as 34 years. Finding large numbers of juvenile bats is a good indicator of a healthy roosting site.
After careful examination, Hall determines that this juvenile male is a Little Brown bat (Myotis lucifugus). Once the data is recorded, she casually drops the bat where she's standing, and it flies off into the night.
A self-described "bat junkie," Hall talks to bats the way other people address kittens or puppies, calling them "cutie," "sweetheart" and "girlfriend." She wears a sweatshirt decorated with glow-in-the-dark bats, and once adopted an Egyptian fruit bat with a broken thumb named "Cleobatra" from a conservation group in Texas. She sports a large tattoo of Cleobatra across the small of her back. "I do belly dancing, so it fits beautifully," she says, adding, "Sanity was never part of my profile."
The idea of handling bats doesn't make me squeamish, but without a rabies vaccine, I can't really help out, even as the traps fill up. Kilpatrick returns, holding a bat with longer ears. This one is larger than the Little Brown one and cheeps loudly. Kilpatrick has been trapping bats since 1974 but it still takes him a minute or two to identify it as a Northern Long-eared bat (Myotis septentrionalis).
By 9:30 p.m., bats are pattering into the plastic pouches like steady rain on a tent. I stand right beside one trap, watching as some of the animals navigate the first layer of fishing line, only to get caught in the second layer. A few swerve just seconds before hitting the net. They seem unfazed by my presence. Hall and Tur are soon scooping up the creatures by the fistful and dropping them into metal canisters.
Nearby, the other biologists stand in a circle, their headlamps lit like miners', identifying age, sex and species, then releasing them into the night.
"Whaddya got?" Darling asks Hall, peering over her shoulder.
"Check out those ears," she says. "Pointy tragus, ears extend over the nose, bald, peachy face."
"Look at the tail membrane."
"I think it's a Northern Long-eared," she decides. "And, he just peed on me."
Moments later, Kilpatrick informs the group that he's caught a Small-footed bat, a rare find. Small-footed bats are identified by a black mask on their face and, obviously, their small feet. Wildlife biologists were decidedly uncreative when it came to naming bat species. Darling explains that biologists don't know whether the Small-footed bat, which roosts on cliffs and in the rubble of rocks, has been harmed by human activity or is naturally rare in Vermont. That's just one more in a long list of bat unknowns.
When Hall finds a bat with stumpy ears, she suggests the anomaly might have been caused by frost damage. Darling isn't convinced. "How can it be frost damage?" he asks. "There's no frost yet!" Kilpatrick offers a couple of theories of his own: Either a predator nibbled on the beast, or it's the result of some environmental toxin inside the cave.
For the next two hours, the group calls out findings -- "female, adult, Long-eared" or "male, Little Brown" -- while Watrous scribbles them down on a clipboard. From time to time, they confer on the identification of a species or let out the occasional "Ow!" as a bat nips a finger. By 10 p.m., the group has captured and identified more than 250 bats. At one point, Darling mutters, "male, Hoary."
"Yeah, right! You wish!" someone shoots back.
The Hoary bat is Vermont's largest, a rare migratory species that can grow to 25 grams. According to Darling, only about nine of the 5000 or so bats that have been trapped in Vermont have been Hoaries. And, as with Vermont's two other migratory species, the Silver-haired and Red bat, scientists don't know whether Hoaries number in the thousands or the hundreds. The Silver-haired bat, which was reportedly very common in the 1800s, has only been recorded once in the last 10 years -- Darling himself has never even seen one in the wild. Where do they migrate? Darling offers some possibilities -- North Carolina, Mexico, the Bahamas -- but admits they still don't know.
During a lull in the activity, Darling pulls out a piece of equipment the size of a portable radio. It's a bat detector, which converts their echolocation into an audible frequency. The device is useful for detecting bat calls as they fly overhead, or for identifying one in hand. To demonstrate, Darling holds it up to a bat, which is vibrating rapidly. The bat detector hisses and chirps like a Geiger counter at Chernobyl.
Next, Darling pulls out a night-vision scope and offers me a peek. The view is astounding. In the greenish field of vision, dozens of bats dart and swirl around our heads. Others move in and out of the mine. Suddenly, it's obvious why I haven't gotten a single mosquito bite all evening. The night-vision scope also dispels another common misperception about bats -- that they tend to get tangled in people's hair. Not one has even brushed me all night.
Although such myths can seem innocuous, public ignorance, fear and even hatred of these harmless creatures can do a lot of harm. Kilpatrick points out that in the years before Fish and Wildlife gated off Dorset Cave, vandals would occasionally enter the site during the winter and burn them off the walls with torches. But even nonmalevolent cave visitors were hurting the bats. Disturbing a bat during its winter hibernation can make it expend as much as 60 days' worth of energy.
Interestingly, when the bats of Austin were first discovered under the Congress Avenue Bridge two decades ago, some people lobbied for their immediate eradication. But after conservationists launched a public education campaign extolling the animals' ecological benefits, public opinion swung from abhorrence to celebration. Today, hundreds of spectators line the shores of Town Lake after sunset to watch the massive black columns of bats emerge into the night sky, where they consume 10,000 to 30,000 pounds of insects before returning in the morning.
The bats have become a boon not only to Texas farmers but also other local businesses. It's estimated that more than 100,000 people visit Austin to see the bats each year, generating about $8 million in tourism revenue. Austin's minor-league hockey team is called the Ice Bats.
Darling doubts that Vermont's bats will ever generate that level of enthusiasm, but he does believe sites such as Dorset Cave and Elizabeth Mine could one day become wildlife-viewing spots. And, a public education campaign that promotes their benefits would help Vermont's farmers, since agricultural pests make up a large part of the bats' diet.
Vermonters should also consider the impact of proposed wind farms on Vermont's bat populations, Darling notes. On the East Coast, wind turbines have taken a greater toll on bats than on migratory birds. For example, biologists were troubled to learn recently that one West Virginia wind farm was killing one bat per turbine each night, a significant mortality rate.
Researchers don't yet understand why. Though they've done acoustic monitoring, radar work and thermal imaging, they're still no closer to explaining why bats are attracted to wind turbines. The rotors may disrupt their echolocation. Or, the turbines' wind patterns may resemble those found at the mouths of caves and mines. Or perhaps the turbines just look like huge roosting trees. "Again, it all gets back to how little is known about bats," Darling says.
By 10:45, the group has wrapped up its survey. In two and a half hours, they've caught 329 bats, including 13 Small-footed ones. They haven't trapped any Indianas, but Darling considers the night a success. Upon reflection, he says it appears that some bat populations are thriving in Vermont.
Still, Darling is cautious about making many declarative statements about these elusive creatures. To illustrate, he cites the example of the huge, dead pine tree in Middlebury where Fish and Wildlife found 270 Indiana bats. Though scientists kept a close eye on the tree, when they went back to survey the roost this summer, there were no Indiana bats there at all. So, they sent volunteers to monitor other known nearby roosting trees, but could only account for 17 of the missing animals.
"How did we lose 253 Indiana bats?" Darling asks, clearly frustrated. "Sometimes with wildlife, the more you know, the more you don't know."