A SPREADING PLAGUE

The fungus, Pseudogymnoascus destrucans, causes white-nose syndrome, the disease that is destroying North America’s bats at a horrifying rate. Bats with white-nose syndrome experience sleeplessness and disorientation that disrupts their physical and mental health. Pseudogymnoascus destrucans, spread by microscopic spores carried by the bats’ fur, causes the bats to rouse more frequently from hibernation.

“This increased waking from torpor is using up their fat stores during a time of year when there are not a lot of insects for them to eat,” Sirajuddin says.

Eventually, the bats starve to death. The fungus can also produce lesions on the delicate skin of the wings, disrupting flight and causing dehydration.

White-nose syndrome is believed to have been brought to North America from Europe. The first cases were found in bats in 2006 near Albany, New York. Since then, the disease has marched rapidly across 31 states and five Canadian provinces. The disease has killed six million to eight million bats across North America.

It only affects bats that hibernate in cold caves and similar structures, such as mines and tunnels, called hibernacula. White-nose typically kills 70 to 90 percent of bats in an infected hibernaculum. Cases of 100 percent mortality have been found.

White-nose syndrome was first found in South Carolina in 2013 near Table Rock State Park and in the historic Stumphouse Mountain Tunnel in 2014. Until 2016, the disease had only affected bats in the eastern U.S., but in March of that year, a group of hikers near Seattle found a dying bat. The U.S. Geological Survey Wildlife Health Center confirmed that white-nose had spread into the western U.S.

Unfortunately for the tricolored bats and fortunately for the Clemson researchers, Pseudogymnoascus destrucans thrives best in 50-58 degrees Fahrenheit, the temperature range of many caves in South Carolina and the Southeast — and exactly that of the tunnel being explored in the fall of 2017.

So as coincidence would have it, the humidity level and temperature that was once ideal for curing Clemson Blue Cheese is also perfect for growing bat-killing fungus.

CONSERVING VULNERABLE POPULATIONS

The value of bats to the North American agriculture industry is roughly $53 billion per year, according to the U.S. Geological Survey. The estimates include the reduced costs of pesticide applications that would otherwise be needed to suppress the insects consumed by bats. Some bat species can eat the equivalent of more than 70 percent of their body mass in insects per night. In an hour, a single little brown bat can eat up to 1,000 insects such as mosquitoes that can carry dangerous diseases, including the West Nile virus.

Bats are also pollinators. Long-nosed bats, which inhabit the dry portions of the North American tropics from El Salvador to northern Mexico, are the primary pollinators of the agave plant, from which tequila is derived. Through pollination, the bats promote the genetic diversity and vitality of wild agave. So, without bats, there might be no tequila.

In addition to the important role bats play in insect and pest control, pollination and seed dispersal, soil fertility, and nutrient distribution, they are also important prey for higher-level predators, such as owls, hawks, raccoons and snakes.

As a researcher, Loeb has been studying bat ecology since 1999. In partnership with scientists from the National Park Service, U.S. Fish and Wildlife Service, U.S. Geological Survey and Canadian Wildlife Service, she created the North American Bat Monitoring Program (NABat).
NABat’s mission is to identify priority bat species for conservation and measure the success of conservation efforts. In 2015, NABat published A Plan for the North American Bat Population that prescribes four approaches wildlife ecologists and land managers can use to gather data to assess changes in bat distributions and abundances: winter hibernaculum counts, maternity colony counts, mobile acoustic surveys along road transects and acoustic surveys at stationary points.

“The disease [white-nose syndrome] has progressed faster than I thought it would,” Loeb says. “It’s only going to get worse and continue to spread until a treatment or cure is found. But we’re continuing to work here on campus and with our partners to understand the spread of this deadly disease and to minimize its impacts.”

Currently 40 states and all 10 Canadian provinces participate in the NABat survey and data collection system.

Last year, Loeb and Jachowski performed a survey of bats at 11 sites in the Sumter and Chattahoochee national forests. They also deployed acoustic technology to record bat calls in an effort to document species variety, as they are doing in Stumphouse Mountain Tunnel. They then compared their findings to data collected at the Sumter and Chattahoochee sites in 2006, the year the deadly disease arrived in the U.S. The survey results were disheartening.

“Bats affected by white-nose syndrome have vanished from some of the survey sites,” Loeb says. “It can take years to rebuild bat colonies, if they can even rebuild at all. Bats don’t reproduce quickly. Most species only have one pup per year, and many of those die.”

As a Clemson University wildlife biology graduate student, Ben Neece led the first South Carolina statewide bat survey as part of the NABat project. The project was funded by the South Carolina Department of Natural Resources.

The goal of the study was to check the efficacy of the NABat survey for South Carolina bat populations, understand the factors affecting detection success and assess environmental factors influencing populations.

Neece used both mobile and stationary surveys to collect bat echolocation sounds from 38 survey cells across South Carolina. The survey sites were chosen for an array of factors, including habitat variety, maximum bat species diversity and low clutter that would interfere with recording.

CREATING SANCTUARIES FOR THE SPECIES

In a project funded by a grant from the U.S. Department of Interior, Katie Teets, a graduate student in Jachowski’s lab, has been using acoustic devices to monitor bat populations at sites in South Carolina and Georgia, while researchers from Virginia collected data from sites in New England and the Mid-Atlantic states.

Teets and her Virginia colleagues surveyed the same sites that were sampled during and prior to the arrival of white-nose syndrome to evaluate whether bat communities have changed since the previous survey.

“We want to understand what habitats need to be conserved and the effect white-nose syndrome is having on individual bat species populations and their habitat use, so it’s very important to understand how population numbers and community structure are being affected by white-nose syndrome and other stressors,” Teets says.

In winter 2016-2017, the Clemson researchers conducted a pilot study of tricolored bats roosting under bridges in the upper Coastal Plain of South Carolina. The preliminary data suggests the tricolored bats hibernating in roosts rather than caves and mines have skin temperature within the optimal range for growing and spreading white-nose syndrome, but that these bats might not stay in torpor long enough for the disease to progress.

Based on the preliminary findings, Loeb and Jachowski received funding from the U.S. Fish and Wildlife Service to further study the roosting bats, using similar technology to the Stumphouse study. The goal is to track the roosting bats throughout the winter to understand their alternate roosting sites and determine their torpor patterns, foraging habits and white-nose syndrome vulnerability.

The data will also be used by the U.S. Forest Service and other land management agencies and transportation departments to inform the management of areas where tricolored bats use roosts rather than hibernacula.

If the data shows that the roosting tricolored bats are less susceptible to white-nose syndrome, then the roosts may be able to serve as refuge for the species and warrant special conservation strategies.

It may even be possible to build roosts specifically designed to serve as winter sanctuaries for the species.

TINY TRANSMITTERS

On the December day that Sirajuddin and her assistant Kayla Goodman make their weekly trek into the darkness of Stumphouse Mountain Tunnel, the condensation from the airshaft drips down upon them. They are carrying fresh battery packs to power the scientific equipment strung out along the length of the tunnel. They will carry the old packs back to the lab to be recharged for future use.

Wearing their Tyvek coveralls and rubber boots, they negotiate the ankle-deep water and tangle of decaying debris and walk along the path to the depths of the tunnel. Sirajuddin stops and points to a bat high up the wall. It is fuzzy, the size and color of a wine cork, and faintly iridescent in the light of our headlamps. And it is by itself.

Photos in nature magazines show caves filled with bats clinging to ceilings and walls shoulder-to-shoulder, guano mounded on the floor beneath them. This is not the case in Stumphouse Mountain Tunnel where the sparseness of the bats that remain make them look alone and vulnerable.

Sirajuddin and her assistant put down their backpacks, battery packs and laptops, and set up a makeshift workstation. They put on surgical gloves, and Sirajuddin stands on her toes stretching to the bat but it is just beyond her reach.

Ideally, she wants to select specimens at equal intervals along the length of the tunnel, but the reduced numbers of Stumphouse bats makes this difficult.

She walks deeper into the tunnel and returns moments later carrying a small white cloth string bag, its contents making it pulse and writhe. Then she opens the bag to give me a glimpse of the tiny tricolored bat that is squirming and squeaking in her gentle grasp.

Sirajuddin sits on the tunnel floor and begins her work, Goodman kneeling at her side with a pencil and clipboard. Sirajuddin keeps the bat in the bag while she weighs it. Then with the fine motor dexterity of a surgeon, she stretches the bat’s wings to check for the lesions that can be a sign of white-nose syndrome. The skin of the bat’s wings is translucent as tissue-paper.

The first time Sirajuddin handled and radio tagged a bat was 2014 when she was working for the University of Tennessee, Knoxville. The first bat she handled was a red bat, and she was under someone else’s supervision.

“I remember feeling extremely anxious because he was so much smaller than I expected,” Sirajuddin says. “It was a long summer of handling bats and taking them out of nets, but by the end of the summer, I felt comfortable and confident.”

She is happy to find that this tricolored bat is lesion free. Next, she parts the fur near the bat’s abdomen to check its sex. It’s male.

Now it’s time to attach the radio transmitter and tag. She reaches in her bag for a small pair of scissors and trims the fur from the bat’s back down to the skin. This will allow the transmitter to collect data on the bat’s physiological patterns during torpor. She puts the fuzz she clipped from the bat into a plastic tube. It will be sent to a lab for testing that will help determine if the bat is local or has migrated from far away to this winter home.

Sirajuddin dabs surgical glue on the radio transmitter and affixes the transmitter to the bat’s back, the antenna as long and thin as a cat’s whisker. In the weeks that follow, the transmitter will send data about torpor temperature and duration to the data logger. After a time, the glue will dissolve and the transmitter will fall harmlessly away.

It is now time to secure a metal band with an identification number to the bat’s wing. The band is the size and weight of a grain of rice. The band number has already been written on the form. She stretches the bat’s wing and uses a small pair of plyers to attach the band, loosely enough that it can slide along the length of the bat’s forearm but firmly enough that it will still be there next year if this squealing, impudent little Perimyotis subflavus is able to avoid the ravages of the disease that is wiping out his brethren.

Normally Sirajuddin would finish by placing the bat against the cave wall where it would instinctively cling, but this specimen is too impatient for formalities, so she raises her arm and opens her hand.

The small bat flies into the darkness, and Sirajuddin continues on with research to ensure its future.