After Dark, DNR Detectives Shed Light on Bats
By Ethan Hatchett
As the sun sets on a humid June day in Macon, Georgia DNR’s bat detectives go to work.
Wildlife technician Rachel Pack mounts a microphone on the roof of an agency truck. At nightfall, she begins driving a preset route through neighborhoods in the middle Georgia city and along county roads just outside it. Her pace is a steady 20 mph.
The rooftop microphone is part of the Anabat, a device that records bat calls. Sporadically, a speaker attached to the Anabat inside the truck cab beeps and screeches. The Anabat is translating into human-friendly wavelengths the high-frequency sounds that bats flying above are emitting. In a process called echolocation, the small mammals use sound to navigate and find prey in the dark.
Anabat microphone mounted to truck roof (Ethan Hatchett/DNR)
“The Anabat also picks up a lot of noise from insects and frequencies from powerlines, but the bat’s sounds are clear,” Pack said. “For example, a cluster of rapid calls may mean a bat is performing a feeding buzz as it homes in on a food source.”
Weeks later, on a July afternoon, Pack joins DNR wildlife biologist Emily Ferrall, fellow technician Jordan Ellison and University of Georgia graduate student Santiago Perea to set up what look like tall badminton nets in the Oconee National Forest near Greensboro. Once done, they again wait for it to get dark.
While using a different method, this summer night shift, like the one is Macon, is focused on the same thing: monitoring bats in Georgia.
“Bat surveys can give us a sense of how our bat populations are doing,” Ferrall explained. “We can get an idea of what species are common, or rare, in an area and the type of habitats the bats are using throughout the year, such as when they have pups in the summer.”
Through these surveys biologists also can detect world-changing threats to bat populations. Without the constant vigilance, many emerging threats and natural phenomena involving bats could remain unknown.
Tracking Trends
During her Macon route, Pack carefully checks the mileage and speed, making sure they are on track and that the recording is as accurate as possible.
After the route is run, the acoustic data will be uploaded for analysis. Software will single out bat calls and biologists will use a call’s frequency and shape to identify the species that made it.
“The mobile acoustic collection method can give us ideas on what species are present where … as we drive through different habitats, and it can tell us about the abundance of these species since we drive at a set rate of speed,” Ferrall said.
Repeat this sampling multiple times during summer, she added, “and we can get an estimate of the reproductive rate of our bats for that year.”
DNR uses the data to monitor long-term trends in the state and also provides it to the North American Bat Monitoring Program to help inform larger bat conservation efforts.
On Oconee National Forest, the monitoring device of choice is a mist net. Ferrall and Pack erect the 6-meter-tall nets in strategic places: two in the middle of the road and one in the center of a creek. Both are areas bats will frequent as they travel corridors to feed or drink.
The fine netting is almost invisible in low light. It is even harder for a bat to notice when chasing an insect. When a bat hits the net, it becomes tangled in the mesh.
Wildlife technician Rachel Pack untangles a bat from a mist net. (Ethan Hatchett/ DNR)
The first four hours are the busiest. Five bats, representing three species, are caught between dusk and dark. Each is quickly untangled, then assessed at a workstation.
The first priorities are to identify the species and determine the bat’s age and sex. Also as part of the process, the bat is weighed, its forearm is measured and its wings are inspected for damage.
The crew handles the bats with care, for the bats and themselves. Masks, gloves and rabies vaccinations are required for workers, although rabies prevalence is extremely low in bats. (Bats carry other diseases, but usually the disease needs to be transmitted to another animal for it to become zoonotic – or infectious to humans – because of the bat’s powerful immune systems.) The masks can also protect bats, helping shield them from COVID-19 if a worker unknowingly has the virus.
A Plague on Bats
After the night is over, the biologists meticulously clean all gear exposed to the bats. But not for the reason most might assume.
In 2007, a fungus now known as Pseudogymnoascus destructans was documented in North America. While bats hibernated in winter, the fungus would attack their bare skin. As it grew, it could cause infected bats to become more active, sometimes spurring them to fly around within their hibernacula or even leave the protective caves and other sites in search of food, wasting precious fat needed to survive winter. A white fluffy substance that accumulated on the muzzle of affected bats led to the disease’s name: white-nose syndrome.
Often called simply WNS, white-nose syndrome has since spread to 38 other states and eight Canadian provinces. Georgia, home to 16 species of bats, documented the disease in 2013.
While white-nose syndrome is the biggest threat facing bats in Georgia, there are others, such as habitat loss. Yet bats are an irreplaceable part of the ecosystem. They act as a natural pesticide, eating pests that would cost farmers more than $1 billion a year in crop damage and losses.
DNR’s bat detectives work night after night to gauge how white-nose syndrome and other issues are affecting bats. The nighttime surveys are helping unravel the mystery of the night so these small mammals that depend on the dark can survive and thrive.
A bat afflicted with white-nose syndrome. (USFWS)
How You Can Help
- Turn your yard into a bat-friendly garden
- Add a bat house on your land
- Minimize the use of pesticides
- Turn off unnecessary lights at night to avoid light pollution
- Volunteer to run an Anabat route to help DNR gather data
- Learn more about white-nose syndrome
Ethan Hatchett is a communications assistant in DNR’s Wildlife Conservation Section.