On an August night in the dense pines of Sumter National Forest in northwestern South Carolina, Susan Loeb and Pallavi Sirajuddin were examining a net stretched across a hiking trail for bats. As the duo were examining the net, the lights from their headlamps settled on a small bat squirming for freedom “We’re catching more than usual tonight,” Sirajuddin said as she stepped towards the net. “Sometimes we come out here and leave emptyhanded,” Loeb added as she untangled the bat.
The absence of clouds and abundance of mosquitos gave them premium access to the area’s bats. Loeb, a U.S. Forest Service research ecologist and Clemson professor, and Sirajuddin, a graduate research assistant, wanted to know how bat populations had changed in the forest since the appearance of white-nose syndrome, a deadly fungal disease that has caused millions of bats to die around the country.
From May to August, the two researchers captured and identified bats at 11 sites in the Sumter and Chattahoochee national forests. They also used acoustic devices to record bats’ echolocation calls, which were used to count the number and species of bats flying overhead at night.
In September, the researchers compared their results to data previously collected at 18 sites in the two forests in 2007, the year white-nose syndrome appeared in the United States. In October, the group presented their findings in San Antonio at an annual conference on managing the country’s struggling bat populations.
Their findings are unsettling.
The group found that some bats have completely vanished from the surveyed sites. Their data suggest that white-nose syndrome, which has killed at least 6 million North American bats, is continuing to spread across areas of northwestern South Carolina and northeastern Georgia.
White-nose syndrome, which is not a threat to humans, targets hibernating bats in caves and abandoned mines. South Carolina has seven of those species, including the big brown bat, little brown bat, small-footed bat, Northern long-eared bat, tricolored bat, Southeastern bat and Rafinesque’s big-eared bat.
Five bat species have tested positive for the disease in South Carolina.
In 2013, the S.C. Department of Natural Resources found a dead tricolored bat at Table Rock State Park in Oconee County and later confirmed it had the disease. “We knew it was coming when it hit the Appalachian chain,” said Mary Bunch, a wildlife biologist with SCDNR. “I’d say it’s living up to expectations.” The disease was later confirmed in Pickens County and Richland County.
Population declines are significant because bats do not reproduce rapidly. “Bats just don’t bounce back from these declines. It can take years to rebuild colonies – and that’s if they even rebuild at all. Most species only have one pup a year, and there’s a high mortality rate when they’re young,” Loeb said. “It’s not looking good for these important mammals.”
The ecological consequences of population reductions are not yet known. But bats are crucial to the ecosystem. Forty-five bat species occur in the United States and Canada, and they represent more than 10 percent of mammals in the region, according to the U.S. Geological Survey.
Because bats eat large amounts of mosquitoes, they can help control viruses spread by insects. That includes West Nile virus, which has been contracted by 44,000 people across the U.S. since 1999, according to the Centers for Disease Control.
They also provide economic benefits.
Bats can save the agriculture industry up to $53 billion per year, according to the U.S. Geological Survey. That accounts for the amount of money that farms didn’t have to spend on insecticides because bats had already eaten the insects.
Some species can eat more than 70 percent of their body weight in insects per night. One little brown bat can eat up to 1,000 insects in a single hour, according to the U.S. Beurea of Land Management. But that number of insects being eaten by bats is dwindling.
For example, one million little brown bats that have already died from the disease could have eaten between 660 and 1,320 metric tons of insects in one year, according to the U.S. Bureau of Land Management.
“The disease has progressed faster than I thought it would,” said Loeb. “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.”
Loeb is working alongside several Clemson University researchers, including Sirajuddin, to understand how the massive bat die-off is altering ecosystems and the structure of bat communities across the Southeast. That team also includes Clemson wildlife biologist David Jachowski and wildlife biology graduate students Katie Teets and Ben Neece.
Together, with an array of federal and state collaborators, the bat researchers are using radio transmitters and acoustic technologies to conduct studies that could have implications for the future management of bats.
A Blueprint for Conservation
The researchers’ efforts are rooted in the life work of Loeb, who has become one of the leading bat researchers in the Southeast. “Her work throughout has established a lot of the basic ecological information we have about bats in the Southeast. I don’t think our projects could have happened without her,” said Sirajuddin.
Loeb graduated from the University of California – Davis in 1987 with a doctorate degree in ecology and joined the U.S. Forest Service’s Southern Research Station in Asheville, N.C. She was then assigned to the Upland Hardwoods Research Unit and located to Clemson University, where she later became an adjunct professor. Throughout the 1990s, Loeb studied flying squirrels and red cockaded woodpeckers. But then the Forest Service redirected her to bats in 1999. Since then, Loeb has devoted her career to answering questions about bat ecology and conservation.
But she’s also worked to minimize the effects of white-nose syndrome.
No one knows for sure how the disease arrived in North America. Though a recent study by the Royal Veterinary College suggest that the disease as brought over from Europe by humans.
The disease was first detected in New York State in 2007. It has since spread throughout 31 states, including South Carolina, and five Canadian provinces.
In 2007, Loeb started catching bats in northwestern South Carolina and Georgia in order to collect data before the disease began to decimate bat populations across the Southeast. “I knew we’d need that data some day,” said Loeb. “I’m just glad we collected it. Because it allowed us to see those declines.”
Loeb partnered with scientists from the National Park Service, U.S. Fish and Wildlife Service, U.S. Geological Survey, Canadian Wildlife Service and other wildlife and conservation groups to create the North American Bat Monitoring Program. “With white-nose spreading, we needed a monitoring program that would allow agencies and researchers to document the impact on bat populations. So the goal was to develop a program that could identify priority species for conservation and measure the effectiveness of our actions to mitigate stressors,” Loeb said. “There really wasn’t anything like it at the time.”
Eventually, Loeb published “A Plan for the North American Bat Monitoring Program,” providing the details that researchers and managers needed to start monitoring bat populations and contributing their survey results to a database. The plan includes four approaches to gathering bat population data:
- Hibernaculum counts made of bat populations in caves and mines in winter;
- Counts of bats in maternity colonies in summer;
- Mobile acoustic surveys along road transects; and
- Acoustic surveys at stationary points.
The program allows researchers to input their data into a Bat Population Database. As data accumulates, the program will issue reports to biologists and managers that reveal trends in the abundance and distribution of North American bats. It will also release periodic reports focused on individual species that are threatened.
Thirty-one states and 10 Canadian provinces use the program.
In March 2015, Loeb was honored with the Forest Service’s “Wings Across the Americas Research Award” for her contributions to the North American Bat Monitoring Program.
She has since continued to research bats, develop conservation plans and coordinate recovery efforts across the Southeast.
The First Statewide Bat Population Study
One of those efforts is the Carolinas Acoustic Bat Survey.
Last spring, Loeb helped Neece secure funding from the U.S. Fish and Wildlife Service for the first statewide bat population study in South Carolina, which he is currently completing with help from SCDNR. “The goal is to find out more about bat distribution throughout the state,” Neece said.
For the past two summers, Neece has collected bat echolocation calls from more than 30 areas across the state. He selected the locations for habitat variety, bat species diversity and low clutter that would interfere with recording. Each summer, Neece started in the Lowcountry and worked his way up to the Upstate. Neece used stationary acoustic samples and mobile acoustic routes to detect the high-pitched frequencies emitted by the flying mammals as they capture bugs and navigate through the dark.
“Bats are notoriously difficult to study. They are active at night, can detect nets and traps, and are fairly secretive when roosting,” said Neece. “So the acoustic surveys really helped me effectively monitor these elusive animals.”
For the mobile acoustic routes, Neece had to drive in each area for two consecutive nights with a bat detector and stainless steel microphone attached to the cab of his green pick-up truck. He would then drive at least 20 mph in order to capture the echolocation calls accurately.
For the stationary surveys, Neece had to place several bat detectors at select spots within the survey areas for up to four nights at a time. The process had to be repeated in the same week each summer.
Neece completed the first phase of his study earlier this summer in Oconee County. Now, he is using classification software to help him identify the calls by species and abundance.
North America has more than 150 bat species, 47 of them in the U.S. “Many bat calls sound the same,” said Neece. “But there are subtle differences by species. The computer software helps me identify them visually since bat calls are at frequencies humans can’t hear.”
His analysis of the second survey should be done next spring. He will then turn over his data to SCDNR, where it will be uploaded to the database and used as the foundation of future North American Bat Monitoring Program efforts in the state.
“The goal is to establish these routes and perhaps add more routes in areas that haven’t been surveyed. It is wonderful that so many people have pulled together to make this happen. After we have the kinks worked out, this can provide a volunteer opportunity for citizen scientists,” Bunch said.
Neece recorded about 30,000 bat calls after noise-filtering technology cut insect sounds and ambient noise. He detected no tricolored bats in several areas of Oconee County.
Trouble for the Tricolored Bat
The tricolored bat has one of the highest mortality rates among bats affected by white-nose syndrome. Throughout areas of the Northeast, the mortality rate for tricolored bats has exceeded 98 percent, according to the Center for Biological Diversity.
“These bats tend to hibernate in the deepest parts of caves, where temperatures and humidity are highest, which are ideal growing conditions for the fungus that causes white-nose syndrome,” Loeb said.
She added that they also hibernate longer, which increases their exposure to the fungus.
In June, the Center for Biological Diversity and Defenders of Wildlife petitioned the U.S. Fish and Wildlife Service to protect the tricolored bat under the Endangered Species Act. The act currently protects the northern long-eared bat and could potentially protect the little brown bat, which is under consideration.
“The tricolored bat is in grave trouble, and it’s time the federal government took action to keep this species from tumbling off the cliff of extinction,” said Mollie Matteson, a senior scientist with the Center for Biological Diversity. “Among the three bats most devastated by white-nose syndrome, the tricolored bat has been virtually forgotten, but that can’t continue if this species is to survive.”
Sirajudden and Loeb received grants from the U.S. Fish and Wildlife Service and U.S. Forest Service last year to understand the vulnerability of tricolored bats to white-nose syndrome in the South. They plan to test whether the skin temperature of tricolored bats during hibernation is within the range for the growth of the fungus Pseudogymnoascus destructans, which causes white-nose syndrome.
Pseudogymnoascus destructans grows in caves with a temperature range of 39 degrees to 59 degrees Fahrenheit, according to a study in the Journal of Applied and Environmental Microbiology. South Carolina caves typically range between 50 degrees to 58 degrees Fahrenheit, according to the U.S. Beurea of Land Management.
Sirajuddin and Loeb will be studying a cave not far from Clemson University that has suffered a major population decline. Its tricolored bat community has been reduced from 321 individuals in 2014 to 67 individuals in 2016, according to Sirajuddin.
In late November, the researchers will dress head-to-toe in white Tyvek suits and venture head first into the darkness with their headlamps. With surgical precision, they will affix small temperature-sensitive radio transmitters to tricolored bats, which are about as small as a wine cork. A nearby radio receiver and data logger will record torpor temperature and duration as well as arousal temperature and duration.
Torpor is the state of decreased physiological activity in hibernating animals. It results in reduced body temperature and metabolic rate. The duo is trying to understand how these patterns make bats more susceptible to white-nose syndrome.
In North America, cave-dwelling bats that hibernate in groups contract the fungus from other bats that have already been infected, often when spores lands on their wings. The fungus then spreads throughout the bat’s body, causing a white growth to form on its nose and wings, according to Sirajuddin.
The disease causes bats to wake up more often during the winter. “The 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 said.
Bats with white-nose syndrome exhibit unusual behavior, including flying outside during the day and clustering near the entrances of caves and mines. The increased activity and lack of food leads to starvation and death. The fungus can also produce lesions on the delicate skin of the wings, disrupting flight and causing dehydration.
The study will also test the assumption that bats come out of their hibernation to forage on warm days during the winter. That tactic could help them survive even if they were infected with white-nose syndrome.
“A lot of scientists thought that as the disease moved south, our bats wouldn’t be hit as hard because of our short, mild winters. They also thought that some of these bats would be able to forage more during the warm days of winter. But obviously, we know that many bat populations are declining despite that prediction,” Loeb said.
The researchers plan to travel to Florida this winter to collect similar data. They have also teamed up with the U.S. Army Research and Development Center, which will collect data from a bat colony in Mississippi for comparison.
Unlike other species affected by white-nose syndrome, tricolored bats extend as far south as Florida and Texas, where they also go into deep hibernation, according to the U.S. Fish and Wildlife Service. “Comparing the results will help us understand whether or not the other bat colonies are vulnerable to white-nose syndrome,” said Sirajuddin. “We’ll be able to somewhat predict how these bats might react to the disease throughout the Southeast.”
She added that their findings would be submitted to the U.S. Fish and Wildlife Service and U.S. Forest Service, which will use it to predict the spread of white-nose syndrome across the region and design more effective treatment applications.
The Caves are Changing
The disease could have significant ecological impacts if it continues to spread.
The average population decline among bat species with white-nose syndrome is 73 percent, according to a 2015 study by Duke University. However, some bat experts estimate that the fungus kills between 75 and 90 percent of an infected cave, according to the U.S. Fish and Wildlife Service.
From 2003 to 2011, Jachowski and his colleagues at Virginia Tech led a study of bats in New York. They observed and collected data before and after the appearance of white-nose syndrome at several sites in Virginia. The researchers found that little brown bats were up to 53 times more active before the disease appeared at the site. And they also found that the disease had decimated the population.
“There’s evidence that the presence of high numbers of certain bat species can suppress other bat species through competition, but we don’t know a lot about the effect of bat species decline on the overall structure of bat communities. Essentially, we are seeing a reshuffling of where and when remnant bat communities are using the landscape. It appears that areas formerly dominated by little brown bats are being made available to other, historically imperiled bat species,” Jachowski said.
He added that the “reshuffling” of these communities could have major implications for how biologists and land managers try to identify areas to protect and conserve the remaining bat populations.
Clemson University graduate student Katie Teets won a U.S. Department of Interior grant earlier this year to partner with Jachowski and Loeb to find out more about how white-nose syndrome is altering the structure of individual bat species.
Teets and Loeb spent the summer capturing bats at survey sites that were sampled during previous studies prior to the arrival of white-nose syndrome. They partnered with a group of researchers at Virginia Tech who completed the same process earlier this summer at survey sites across New England and the Mid-Atlantic.
“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 said.
The researchers will complete the study in 2018.
Saving the Bats
The efforts by Clemson researchers are part of a bigger picture.
“Our goal is to help forest managers and policy makers,” said Susan Loeb. “They can then use our findings to focus treatment efforts; implement better forest management techniques; and protect certain species under state or federal law.”
Loeb said that an endangered species listing is the best option for Southeastern bat populations at the moment. She says, “There is no cure for the disease. But there are a few treatments being tested. Really, conservation is the only option for now.”
In 1973, Congress passed the Endangered Species Act to protect and recover imperiled species and their surrounding ecosystems. The U.S. Fish and Wildlife Service and the National Marine Fisheries Service oversee the program and maintain a listing of imperiled species, ranging from mammals to insects.
Species may be listed as endangered or threatened. The term “endangered” means that a species is in danger of extinction throughout all or significant portions of its range. And the term “threatened” means that a species is likely to become endangered in the future, according to the U.S. Fish and Wildlife Service.
The law requires the U.S. Fish and Wildlife Service to ensure that management actions don’t threaten the listed species. That includes the destruction of habitats. The law also prevents the “taking” of any listed species from its habitat.
Designating a bat species as threatened or endangered triggers regulations and protective measures designed to help boost the species population and protect them from harassment from humans. That includes restricting some tree removal from forested areas, especially in the summer months when newborn bats are nesting.
South Carolina also offers similar protection through the state Nongame and Endangered Species Act. SCDNR also maintains a list of native species that need protection. That list includes bats.
Twelve of South Carolina’s 13 bat species are on the list of South Carolina’s “Species of Greatest Conservation Need.” The Rafinesque’s big-eared bat is South Carolina’s only endangered species, and the Eastern small-footed bat is the state’s only threatened species, according to Bunch.
SCDNR also assesses population data for species and ranks them. That ranking decides how the state allocates resources to protect species. “The rankings are flexible,” said Bunch. “It’s also based on input from researchers, like Susan and David. We’re actually adjusting our current rankings now.”
Bunch added that the state recently sent a survey to bat researchers across the state. That survey will gauge their input and research results. The state plans to complete the survey in November. “The research influences priorities. So we look at these studies and their findings to determine the best course of action,” Bunch said.
She added that the listings could be complete by 2017.
SCDNR then plans to update its Bat Conservation Plan, which provides natural resource managers and researchers with the updated rankings and a detailed guide to the methods and regulations that must be used to protect bats.