Appalachian Laboratory

Bat scientists seek answers on emerging disease

White-nose syndrome devastating already vulnerable bat populations

She arrives before the sun sets and stays well after.

Casting a spotlight on the hardships of bats means Beth Stevenson, a faculty research assistant at the University of Maryland Center for Environmental Science’s Appalachian Laboratory, spends a lot her working hours outside in the dark, waiting.

For three seasons of the year, she can be found at the edge of streams, nearby caves or abandoned mines, and alongside other places where bats live, eat, and roost. Stevenson has been working to understand how a deadly bat disease called white-nose syndrome, which was first detected in Maryland in 2010, has affected populations of different bat species.

Kelly Pearce tries to read the weight of a bat (in bag) as Kevin Hesse holds it in place.

“The disease is still emerging, and we don’t know a lot about what’s happening to bat populations,” Stevenson said. “To me, it’s exciting to be working with a species that I think is really important: very diverse, very biologically interesting, and ecologically valuable.”

Often by her side are Kelly Pearce, a graduate student and research technician, and Kevin Hesse, a biological field technician, who are also from the Appalachian Laboratory in Frostburg.

Through the summer, they spend three nights per week in the field. One of their work spots was a wooded clearing off a private country road in Maryland’s Carroll County where they hoped to find the federally endangered Indiana bat.


They positioned fine mesh nets on tall poles so the nets draped just over a creek and stretched up about 24 feet to the tree canopy. Then they set up folding chairs around a small table that would serve as their work bench and waited. Their goal was to catch bats in the netting as they flew along the creek. They would be able to collect a bat from the net, take a few samples, and let it go in a matter of minutes.

Using headlamps as their only light when night fell, each team member fulfilled a task: Hesse took the notes and Stevenson helped Pearce who was in charge of taking the samples. The team is relatively quiet when they are working with a bat. Buzzing crickets, chirping bats, and other background sounds of the night fill the air instead.

Kelly Pearce checks for any damage in the wing of a bat.

Each sample could hold clues about that bat: Their fur can offer clues about migration, their wing tissue samples can unlock genetic data, and any orange flecks visible under a black light signify the fungus that causes white-nose syndrome. None showed signs of it. They also weighed and sexed each bat (Stevenson determined two were pregnant).

Because Pearce was handling the bats, she wore white plastic coveralls and baseball batting gloves—which experience has proven are toughest against bat bites. Everyone, including Pearce over her batting gloves, wore a new pair of blue nitrile gloves for each bat they handled to avoid spreading any diseases from one bat to another.

Pearce talked to the bats as she worked, trying to make them calm in her hands.

“The big brown ones especially can get kind of feisty with you, but a lot of the work is just trying to control their wings, to keep them still,” she said. “We try to process them accurately, but quickly. We don’t want to cause them any more stress than what the process already does.”

After handling eight bats in a row, she got a break. They caught several in their net around 9:30 p.m., which Stevenson calls their golden hour for captures.

If you go back and look at what folks were catching before white-nose syndrome, they were catching a lot of bats per night, anywhere from 10 to 20. Now if we catch one or two, we consider it a good night.

Beth Stevenson
Faculty Research Assistant, Appalachian Laboratory


Stevenson picked this remote Carroll County location because her predecessor successfully trapped the Indiana bat in the same spot in 2007.

Even before white-nose syndrome became a problem in Maryland, habitat disturbance and pesticide use had killed off enough Indiana bats to make them a federally endangered species. Ten years after her predecessor’s survey, she is wondering if Indiana bats are still there.

Big brown bats have been less susceptible to white-nose syndrome.

Indiana bats are one of 10 species of bats native to Maryland. The state is home to four tree bats—the eastern red, hoary, silver haired, evening bats—and six cave bats—the eastern small-footed, little brown, northern long-eared, Indiana, tri-colored, and big brown bats.

Largely because of white-nose syndrome the Maryland Department of Natural Resources classifies all 10 bats as Wildlife and Species of Greatest Conservation Need.

White-nose syndrome is a fungal disease that spreads from bat to bat in close quarters, such as the caves they go to during the winter. It isn’t fatal on its own, but it grows on their wings, muzzles, and other membrane areas while they hibernate and eventually become bothersome enough to wake them too early. The bats can then die from starvation or dehydration before winter ends.  

Some bats, such as big browns and eastern reds, are less susceptible to the disease and are likely more common for any Maryland resident to see. Big browns tend to be tough enough to fight the disease and red bats happen to migrate away from caves where the disease has been an issue.

PHOTOS: A night in the life of a bat scientist

When the team captures a northern long-eared bats like this one, they will insert a transmitter to track it by day.

Bats from the genus Myotis, or the mouse-eared species, including the Indiana bat, little brown bat, and northern long-eared bat, have been more vulnerable to the disease.

“As Indiana bats and other white-nose affected species are becoming rare on the landscape, we’re capturing more big brown bats,” Stevenson said. “The question is then, are big brown bats filling the niche that the white nose-affected species once occupied?”

On this particular summer evening in Carroll County, the bat team caught 13 big brown bats and one eastern red bat.

In 30 surveys this summer at locations in Maryland’s Garrett, Allegany, Washington, and Carroll counties, the team captured 143 bats, the overwhelming majority of which were big brown and eastern red bats.

While the Carroll County work was designed around Indiana bats, the western Maryland surveys were part of a Maryland Department of Natural Resources-funded project targeting northern long-eared bats.

Northern long-eared bats were the only federally listed species that the team captured this summer. They caught two and as in previous years, Stevenson tagged them to track. Knowing where a bat roosts during the day can help guide management practices that can protect that bat.

Beth Stevenson gets a closer look at a bat she thinks might be pregnant, while Kelly Pearce holds it steady.

The diversity of species caught, or in this case, the lack of it, is a hint of the effect of white-nose syndrome.

“The species composition has changed a lot since before white-nose,” Stevenson said. “Before the disease emerged, people were catching a lot of species that belonged to the genus Myotis. If we catch one of those now, it’s rare because those are the species most affected by the disease. The species composition of bats that we’re catching has shifted to mostly big brown bats and red bats.”

Regardless which project Stephenson is working on, the bat team’s purpose is the same for every outing: Capture bats to study, note species diversity and presence of the fungus that causes white nose, release, and repeat. Collecting data over decades can reveal a lot about how bat population numbers respond to the disease.

With bat populations dropping, however, Stevenson feels lucky to catch any bats at all.

“If you go back and look at what folks were catching before white-nose syndrome, they were catching a lot of bats per night, anywhere from 10 to 20. Now if we catch one or two, we consider it a good night,” she said.

There is a lot of time spent waiting and during those quieter moments, the team members may play card games (Rummy and Cribbage are favorites) or catch up on work, but mostly, they talk.

“I feel like I know everything about everyone on the team,” Stevenson said, laughing.

Kelly Pearce checks for damage in the wing of a bat during a summer night in the field. Wing scars could be a sign of white-nose syndrome.

She adds that they also spend a lot of time reading. A carefully positioned headlamp on a Nalgene water bottle can make a good lantern.

On longer breaks, the curious scientists explore the area and the creatures in it.

“If we’re by a stream, which is most of the time, we’ll flip rocks for salamanders or look at the stars,” Pearce said.

Stevenson added: “The coolest thing about working at night is that you see wildlife and things that you wouldn’t normally see because they’re out at night. We see deer, bears, foxes, snakes. We catch flying squirrels in our nets all the time.”

Lightning bugs are almost always in view, as are moths.

“We’ll get imperial moths, luna moths, and rosy maple moths, which are highlighter pink and highlighter yellow; they’re super cool,” Stevenson said.

Stories by flashlight, identifying frogs and salamanders, the occasional unidentifiable sound—a night with the bat team has a summer camp feel.

“The summer nights are a little bit more enjoyable than our fall and spring surveys,” Pearce said. “During the fall and spring, it gets down to 50 degrees and you’re just sitting outside.”

“Or lower,” Stevenson chimes in. “Remember that one night it was 35 degrees, at the one site where we never catch anything?”

The cold nights are harder and time seems to pass more slowly, but that field work is done across western Maryland and the views are their reward.

“We have some sites where we’re pretty much guaranteed to catch bats and the scenery, with the streams and everything, it’s just incredible. It’s gorgeous,” Stevenson said.

From June 6 to August 15, the Appalachian Laboratory bat team conducted 30 surveys. This chart shows the number and type of bats captured at each site.
Species Number Captured Percent of Total Captures
Big brown 67 46.9
Hoary 1 0.7
Eastern red 62 43.4
Little brown 4 2.8
Northern long-eared 2 1.4
Tri-colored 1 0.7
Unknown 6 4.2
Total 143