Working the night shift: Scientists seek answers as bat populations change

October 26, 2017

For the bat scientists at the University of Maryland Center for Environmental Science, the busiest part of the work day happens well after most people have ended theirs.

We joined Beth Stevenson, a faculty research assistant at UMCES' Appalachian Laboratory, and members of her team for a night in the field and as we wait in the dark for bats to come, we discuss what have they have so far learned about a disease killing off some bats in Maryland. We also talk about some of their favorite bats, misconceptions, and overall get a better appreciation for the oft-misunderstood creature of the night and the scientists dedicated to saving them.


Read the story that accompanies this podcast.

Story transcript

Casting a spotlight on the hardships of bats means spending a lot time in the dark… waiting.

It can be cold, sometimes even boring, but for Beth Stevenson, a faculty research assistant at the University of Maryland Center for Environmental Science’s Appalachian Laboratory, it’s a worthy cause.

BETH STEVENSON: To me, it’s exciting to be working with a species that I think is really important: very diverse, very biologically interesting, and important ecologically.

Some bat species are in decline, and one of the reasons is a disease we still don’t fully grasp. White-nose syndrome comes from a fungus that bats acquire and spreads in caves. It isn’t fatal on its own, but it grows on their wings, muzzles, and other membrane areas while they hibernate and eventually becomes bothersome enough to wake them too early. The bats can then die from starvation or dehydration before winter ends.  

It was first detected in Maryland in 2010, which is home to 10 species of bats. Largely because of white-nose, Maryland Department of Natural Resources counts all 10 among its Wildlife and Species of Greatest Conservation Need. (View the State Wildlife Action Plan)

Stevenson has been working to learn more about how much the disease could be affecting Maryland’s bats. For three seasons of the year, she can be found at the edge of streams, nearby caves or abandoned mines, and other places where bats live, eat, and roost.

But she doesn’t have to do it alone. 

KELLY PEARCE: My name’s Kelly Pearce. I am one of Beth’s research technicians on the project and also am a graduate student at the Appalachian Lab doing my Ph.D. on river otters.

KEVIN HESSE: And my name’s Kevin Hesse, also a biological field technician for Appalachians Lab and I’m working on past undergraduate experience.”

And for one summer night in Carroll County, we joined the team, too, to see how they study bats, what they look for, and what they do while they’re waiting to catch one.

Our evening starts around 8:30 p.m. when the sun is still up but barely. The day’s last light is a guide as they set up, their folding chairs ring around a small metal table that will serve as their work station. A brown paper bag that will hold fur and tissue samples is taped to the table side and freshly cleaned instruments needed to take those samples are set on top.  

PEARCE: We have the set up pretty much down.

Pearce has even got batting gloves to protect her hands from bat bites. Need some extra light? A headlamp on the right kind of water bottle makes for a great lantern in the field. Like any scientist they’ve learned to be resourceful when they need to.

Their work area ready, they then set up the nets they need to capture the bats. 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.

They like to use corridors, so the idea is those bats are flying along the stream, maybe they’re headed to this pond right here to catch some bugs, as the bats are flying down the stream, they’ll hit our net.

Now that everything’s ready, we wait for dark to fall and the bats to come.


We talk while we wait.

STEVENSON: Most of my research experience has been with mammals in general. I started working with bats in 2012 with U.S. Fish and Wildlife Service up in New Jersey. I was really interested in bats at the time because that was shortly after white-nose syndrome emerged. I was really fascinated by how bats might respond to the disease and how they were already beginning to respond as far as their population numbers. Working with bats is really relevant since the disease is still emerging and we still don’t know a lot about what’s happening to bat populations.

The goal of this survey specifically in Carroll County is to capture Indiana bats. Of course, we take measurements on any of the bats that we capture, so it really on a broader scale provides information on the bat community in the area.

Indiana bats have been listed as federally endangered for a really long time. There’s a lot of interest in understanding how white-nose affects them, but they were actually endangered before white-nose was ever an issue, so things like habitat loss, pesticide use were some of the factors that were causing their decline and caused them to ultimately be listed.

This is a site where Indiana bats had been previously caught. In 2007, a predecessor of mine had done the same thing – had put up mist nets and captured them and the reason why he was here was because some researchers had originally captured them in Pennsylvania and had attached radio transmitters to them that allowed them to track their movements. And they found them here.

So about 10 years ago, my predecessor, Joshua Johnson, did some acoustic work, set up mist nets, and actually captured them. He attached radio transmitters as well, and tracked them.

Our goal is to see if they’re still around.

This is all private property and there were several sites where he put up acoustic detectors and mist nets, there were several sites throughout the property and he was able to get them.

This is actually a smaller project. We have two projects going on right now. The one is monitoring bats in western Maryland. For that project, we have eight sites in western Maryland in Washington, Alleghany, and Garrett counties. All of them but one are on public lands, so wildlife management areas, state forests, state parks.

The purpose of that is to compare the numbers of bats we’re catching now to what we were catching before white-nose syndrome, but also in hopes of catching a rare, threatened, or endangered species and putting a transmitter on it and collecting habitat data. This project is specifically in hopes of catching Indiana bats since this was a historic capture site.  

If at all she sounds distracted, it’s because she’s multi-tasking – while she talks, she listens. Without prompt, one of the members of the team will occasionally stroll over to their net – about 30 yards from the work station – to look for any new catches.

They know how to capture a bat, but not when it will happen, so they need to be ready. It may even happen mid thought.

STEVENSON: It’s busy work but it’s fun – and we’ve got a bat!

So we had a bat that flew into the lowest part of our net. This is a big brown bat. This is most of what we’re catching these days. Kelly in her full Tyvek garb is going to take this guy out.

They may hope to catch a certain species, but they are happy with any capture. Any bat could have information they need.

STEVENSON: This data helps us understand how populations are changing in response to white-nose syndrome. So we can take these data as far as how many bats we’re capturing in a night and how many different species we’re capturing, and compare those data to capture results before white nose was an issue. That can help us understand the impact white nose is having on bat populations as a whole in certain areas of Maryland and it helps us understand which species are more important for conservation, sort of like a triage.

Using headlamps as their only light in otherwise total darkness, each team member fulfills a task: Hesse took the notes and Stevenson helped Pearce who was in charge of taking the samples.

HESSE: So basically it’s like general age, how much the bat weighs, whether juvenile or adult, if there’s any damage to the wing – which is the wing score, with the fluorescent light we’re looking for potential spore spots of the disease.

None of the 14 bats they would catch this evening showed signs of white-nose syndrome infection.

None were the Indiana bat either.

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

By the end of their summer capture season, the team will have done 30 surveys across Maryland’s Garrett, Allegany, Washington, and Carroll counties, capturing 143 bats, the overwhelming majority of which were big brown and eastern red bats.

That lack of diversity could be the white-nose effect.

STEVENSON: If you look at the species composition, it’s changed since before white-nose syndrome. Before white nose, people were catching a lot of species that belonged to the genus Myotis and those are the species that are most effected along with some other species like tri-colored bats. If we catch one of those now, it’s rare. The species composition of bats that we’re catching has shifted to mostly big brown bats and red bats.

Some bats, such as big browns and eastern reds, are less susceptible to the disease. 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.

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

UMCES: So, is it that the Indiana bats are rare or the big brown bats are just so common?

STEVENSON: Both, so I think what the science in other areas has generally shown is that big brown bats and other species are in decline because of white nose, as those species are becoming rare on the landscape, we’re catching more big brown bats. The question is then, are big brown bats filling the niche that the white nose-affected species once occupied?”

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 with transmitters.

STEVENSON: The sound that you’re hearing here is the sound that the radio transmitter that would be attached to a bat would emit. So if we attach this to a bat, then we would be able to use this receiver along with an antenna to track a bat and figure out where it’s spending its time during the day or where its foraging.

UMCES: Do you have any bats now out there with transmitters?

STEVENSON: We do; I was out earlier tracking it. My team and I were lucky enough to capture a northern long eared bat. It was an adult male that we captured in western Maryland in a wildlife management area and because northern long eared bats are federally threatened species we are interested in knowing where their day roost trees are and that gives us information on how to manage the areas where they’re spending their time.

While they don’t end up catching the kinds of bats they want to track with transmitters, this one summer evening in Carroll County is a good night for the bat team. Before white-nose syndrome, the bat team was catching maybe as many as 50 in this area.

STEVENSON: Now if we catch one or two, we consider it a good night.

And they caught 13 – many in quick succession. Before they could pluck the first bat from the net, two more arrived. It’s just shy of 9:30.

[Bat chirping and background chatter from the team as bats fly into their net]

STEVENSON: This is our golden hour.

For the most part, the team is silent when they work, focused on the bat whose chirps fill the void.

Pearce occasionally talks to the bat in her hands as she works, her way of trying to keep it calm.

PEARCE: Handling the bats is always kind of a fun opportunity. The big brown ones especially can get kind of feisty with you, so a lot of it is just trying to control their wings, to keep them still while you’re taking the measurements to get your measurements as accurate as possible. Mostly it’s just trying to keep them calm. We try to process them accurately, but also quickly. I tend to talk to the bats a little bit; I don’t know if it really helps them calm down or not, but we don’t want to cause them any more stress.

Evenings like this one have taught each member of the bat team a lot about the oft-misunderstood mammal.

HESSE: They’re definitely a lesser known but very ecologically important animal. They’re cool little species.

STEVENSON: People should definitely not be afraid of bats. If you find yourself near a bat, that bat, just like most other wild animal, they do not want to be near you. So a lot of people think that bats will fly into your hair and get tangled. In fact, bats are really good at moving around at night.

UMCES: Why do you think they have such a bad rap?

STEVENSON: So a lot of people when they think of scary bats, a lot of folks are thinking of vampire bats. A lot of people think bats are going to suck your blood.

Of well over 1,000 bat species, only three of them consume blood.

STEVENSON: None of those bats are in North America. Those bats are in places like Central America and South America. All of our bats in Maryland are insectivorous, which means that they eat insects.

That’s where a lot of people’s fears come from, they see bats and they see their long teeth and they think that’s an animal that wants to bite me and in fact their teeth are evolved to be eating things like beetles, insects with hard exoskeletons, so that’s why they’ve got those sharp pointy teeth, not to bite people, but for their food.

A lot of people are afraid of bats in their house because they think that all bats have rabies. In fact about less than 1 percent of bats have rabies. Any animal can have rabies. I think it’s important to understand not all bats are dangerous and not all bats have rabies, but to call the appropriate person to remove it from your house.

UMCES: Do you guys have favorite bats?

PEARCE: My favorite bat is the small-footed bat. Just because their size, they’re kind of cute, and if I’m not mistaken they have like a black kind of mask around their eyes, so I just find them kind of endearing because of their size and their coloration.

HESSE: I think the northern long-eared bat. It was the rare one we caught a few days ago. It was the first time that I’ve ever attached a transmitter to a bat. We caught this super rare bat, recorded all the information and then attached a transmitter to it, released it and then the next day got out the radio telemetry stuff and started searching for it. It was just a really cool experience finding that rare of a bat at one of the sites we’ve been working at all summer. 

STEVENSON: As far as my favorite bat that occurs in Maryland, I love hoary bats. Hoary bats are Maryland’s biggest bat; they weigh up to an ounce so they’re very big.

I feel like I would have a hard time picking, out of all the bats, a single favorite bat. Florida bonneted bats I think are very interesting. These guys are endemic to a very small area in south Florida and they’re considered one of the most endangered mammals so we don’t exactly know how many there are, but they’re also really big bats, about the same size as hoary bats. They have these kind of folds in their face where their ears fold down and that’s why they call them bonneted bats, it kind of looks like it’s wearing a bonnet.  

There’s this species of bat. They make tents out of leaves…

This is the aptly named tent-making bat.

STEVENSON: They’re in the tropics. They bite into these leaves along the spine of the leaf, so if you think of a really big tropical leaf and they cause the leaf material on either side of the central spine to fall down and it creates this tent and then these bats roost in a line along the central rib along this tent that they made.

They don’t stay there for long so they do this constantly. They’re always moving around from leaf to leaf and making a new home and it think that’s just, it’s amazing.

Bats are so diverse – in what they look like, the habitat they use, their prey. It’s just amazing.

These conversations are the ones that the bat team has between bat captures. The team members play card games (Rummy and Cribbage are favorites) and other times they catch up on work, but mostly they talk.

STEVENSON: I feel like I know everything about everybody. I’ll do some habitat observations.  

PEARCE: If we’re by a stream, which is most of the time, we’ll flip rocks for salamanders or look at the stars. We do a lot of reading.

STEVENSON: The coolest thing about working at night is that you see wildlife and things that you wouldn’t normally see because you’re out at night. We see deer, bears, foxes. We catch flying squirrels in our nets.

PEARCE: The summer nights are a little bit more enjoyable than our fall and spring surveys because fall and spring, it gets down to 50 degrees and you’re just sitting outside.

STEVENSON: Or lower. Remember that one night it was 35 degrees at the one site where we never catch anything?

PEARCE: Those nights we’re in winter jackets, full spandex, field pants and winter hats, there’s no warmth anywhere.

STEVENSON: You wear a lot of layers. We have hand warmers. Those are really quiet nights. It’s beautiful out there.

PEARCE: It is really nice.

STEVENSON: We have some sites out there where we’re pretty much guaranteed to catch bats and the scenery with the streams and everything is just incredible, it’s gorgeous.

It can be cold, and it can be slow, but the payoff for those nights in the field is clear: The bat team may finally answer some important questions that could help save threatened species.