• STUMPHOUSE TUNNEL SLEUTHS

By Jonathan Veit
Photography by Ashley Jones

Researchers at Clemson are on the forefront of a national effort to understand why bats across North America are dying in tragic numbers and to divine how this massive die-off is shifting the structure of bat communities and altering fragile ecosystems.

AS SHE STANDS before the gaping, dripping entrance of Stumphouse Mountain Tunnel zipping into her Tyvek coveralls, graduate research assistant Pallavi Sirajuddin says, “Word of caution: Last week there was a copperhead just off the path in chamber B of the tunnel. If it is there again today, I will point it out to you.”

It is a clear late-fall day in the mountains north of Walhalla, just 20 miles from Clemson. Sirajuddin and a cohort of researchers are here to set up a complex tangle of coaxial cable, aerial antennas, super-sensitive listening devices and data loggers, with battery packs to power it all, along the 1,600-foot tunnel.

A few weeks from now, when the weather grows colder and tricolored bats turn Stumphouse Mountain Tunnel into their winter home, Sirajuddin and an assistant will begin applying tiny radio transmitters to the backs of the small creatures.

By recording body temperature and arousal patterns, these radio transmitters will help the researchers understand how decreased physiological activity during hibernation — known as torpor — makes the tricolored bats more susceptible to white-nose syndrome, the deadly fungal disease that is wiping out populations of bats across North America. The researchers will then compare data collected from the Stumphouse bats to data they collect from a healthy tricolored bat community that is hibernating in a cave with similar temperatures in Mississippi.

Nine bat species, including two endangered species and one threatened species, have been confirmed with white-nose syndrome in North America. The tricolored bat is not currently on the federal threatened and endangered species list, but reviews are being done to determine whether it should be listed, primarily due to mortality from white-nose syndrome.

Clemson’s location in the Southern Appalachians within a short distance of hibernation spaces such as Stumphouse Mountain Tunnel gives these researchers unique opportunities to make discoveries that might one day thwart or impede the scourge of white-nose syndrome.

ON THE FOREFRONT OF A NATIONAL EFFORT

THE BLUE RIDGE RAILROAD began tunneling into Stumphouse Mountain in 1852 in an effort to build a railroad through the mountains to Knoxville, Tennessee, but construction was disrupted by North-South hostilities, and momentum for the railroad ebbed. In 1940, a Clemson A&M dairy science professor recognized the tunnel might be perfect for curing blue cheese. Clemson bought the tunnel in 1951 and used it as the ideal place to cure cheese until 1956.

On this fall day, we walk across the pea-gravel floor of the public part of Stumphouse Mountain Tunnel, the sound of our footfalls echoing off graffitied granite walls.

“We’re going all the way to the back of the tunnel,” Sirajuddin says. “Then we’ll set up the equipment as we work back toward the entrance. We can talk, but it’s best to whisper so we don’t disturb any bats we find.”

The bats we find will be few and far between on this day. It isn’t cold enough yet for them to begin hibernating in the tunnel, and white-nose has already taken a devastating toll on the Stumphouse bats. Their numbers have plummeted from 321 individuals in 2014 to just 37 in 2017.

The numbers of Stumphouse bats have plummeted from 321 individuals in 2014 to just 37 in 2017.

Sirajuddin’s mentor, Susan Loeb, follows closely behind. Loeb is a renowned Southeastern bat researcher, Clemson adjunct professor and research ecologist for the U.S. Forest Service Southern Research Station. She co-leads a robust multipronged bat research group with David Jachowski, assistant professor of wildlife ecology in Clemson’s Department of Forestry and Environmental Conservation.

The light from the tunnel entrance is still reaching us when we arrive at a gate of iron bars, secured by a heavy chain and padlock because of instances of falling rock. Sirajuddin opens the gate, and we step through. We are at the midway point of the tunnel, and a 16-by-20-foot airshaft punched into the mountain above us extends upward 200 feet to the surface. The upper rim of the airshaft is ringed by mountain laurel and rhododendron. We are now standing in ankle-deep water and a snarl of decaying boughs fallen through the airshaft over the years.

Sirajuddin closes and locks the gate behind us, and we turn on our headlamps and stumble our way through the fallen branches and slick rocks to a pathway bordered by railroad ties. Sirajuddin is out front. “Copperhead to the right,” she stage-whispers.

A few more steps and the shafts of light from our headlamps find the snake on the path, head slightly raised and looking mildly perturbed.

For this particular team of scientists, research goes beyond microscopes, shiny laboratory equipment and pristine white lab coats. Here, it takes the brute strength of pack mules, the technological skill of computer networkers and the soul of an explorer to be on the forefront of a national effort to understand why bats across North America are dying in tragic numbers and to divine how this massive die-off is shifting the structure of bat communities and altering fragile ecosystems.

A SPREADING PLAGUE

THE FUNGUS Pseudogymnoascus destructans causes white-nose syndrome, the disease that is destroying North America’s bats.

Imagine every few hours, night after night, an unknown irritant wakes you from your sound sleep. Imagine how this would affect your physical and mental health and how disorienting it would be.

This is what happens to bats with white-nose syndrome. Pseudogymnoascus destructans is spread by microscopic spores carried by the bats’ fur, and it 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, killing 6 million to 8 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. Ten counties in the state have now been reported to have the fungus, with three of those added in March 2018. 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 destructans 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.

Susan Loeb makes adjustments to monitoring equipment in Stumphouse Mountain Tunnel.

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 costs of pesticide applications that would 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 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. Currently 40 states and all 10 Canadian provinces participate in the NABat survey and data collection system.

The value of bats to the North American agriculture industry is roughly $53 billion per year, according to the U.S. Geological Survey.

“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.”

From 2003 to 2011, Jachowski and colleagues at Virginia Tech led a study of bats in upstate New York that was published in the journal Diversity and Distributions. The study spanned the time immediately prior to and following the first appearance of white-nose syndrome in the region. The researchers found that before the disease outbreak, the species of bat known as the little brown bat was five to 53 times more active than all other bat species. Little brown bats were also consistently detected during evening hours.

Following the arrival of white-nose syndrome in 2006, little brown bats and other cave-roosting bat species have been decimated. Results from the New York study suggest that the direct die-off of little brown bats is causing behavior changes in other bat species not directly impacted by white-nose syndrome. The unaffected bat species are filling the spatial void left in the less-occupied night skies. The ecological implications of this shift are unknown.

Jachowski believes this could have major implications for how biologists and land managers try to identify areas to protect and conserve remaining vulnerable populations.

South Carolina is home to 14 bat species.

CREATING SANCTUARIES FOR THE SPECIES

IN A PROJECT FUNDED by a grant from the U.S. Department of the 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 prior to and following 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 2016-17, the Clemson researchers conducted a pilot study of tricolored bats roosting under bridges in the upper Coastal Plain of South Carolina. The preliminary data suggest 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 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 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 show that the roosting tricolored bats are less susceptible to white-nose syndrome, then the roosts may warrant special conservation strategies.

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

Pallavi Sirajuddin prepares to attach a radio transmitter to a bat.

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 air shaft drips down upon them.

Wearing their Tyvek coveralls and rubber boots and carrying replacement battery packs, 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 makes them look alone and vulnerable.

Sirajuddin and Goodman put down their backpacks, battery packs and laptops and set up a makeshift workstation. They put on surgical gloves, and Sirajuddin walks deeper into the tunnel, returning moments later with 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.

Pallavi Sirajuddin preparing bat to attach transmitter.

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 lesions. The skin of the bat’s wings is translucent as tissue paper.

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 pliers 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 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 with her research to ensure its future. 

Jonathan Veit is communications director for Clemson PSA and the College of Agriculture, Forestry and Life Sciences.