- nature.org/artificial bat cave
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- Hear the NPR report on the cave.
- Read the New York Times story on the cave.
- See inside the artificial cave with the CBS Evening News.
To fight white nose syndrome, an epidemic that is causing catastrophic die-offs in America’s cave bat populations, The Nature Conservancy in Tennessee has embarked on a radical idea.
Building an artificial cave next to an existing natural bat cave in Tennessee. The artificial cave can be disinfected of the tell-tale white fungus that causes white nose syndrome—thus creating a healthier haven for bats.
Following expert scientific review of the building plans, The Nature Conservancy began construction on the artificial cave in August 2012 and finished construction in early October to allow bats to take up residence this winter.
Nature.org talked with Cory Holliday, cave and karst program director for The Nature Conservancy in Tennessee.
Extra: Read Nature Conservancy blogger Matt Miller's series about the artificial cave.
Evan McGlinn for The New York Times
A researcher from Boston University collected and tagged bats at a barn in Massachusetts.
LARKSVILLE, Tenn. — For about six years, Cory Holliday, theNature Conservancy’s cave specialist in Tennessee, has feared that white nose syndrome, a devastating fungal disease that kills hibernating bats by the millions, would come to Bellamy Cave. Last winter it did.
A few bats were found with the telltale fuzzy white growth on the muzzle, and Mr. Holliday (a distant relative of the original Doc Holliday of O.K. Corral fame, or infamy) knew it was time to act.
The disease, for which there is no treatment and no cure, was first spotted in New York in 2006. It spread to New England and has steadily moved south and west, crossing the Mississippi and just recently reaching Alabama. More than five million bats have died.
The disease does not affect humans. But bats eat prodigious numbers of insects, and one study estimated that if the death toll continued to rise, the cost to farmers in increased use of pesticides would be in the billions.
In Tennessee, a state with 10,000 caves and 16 species of bats, about half of them hibernating, Bellamy is something special. It is the winter home, or hibernaculum, to 270,000 gray bats, listed as endangered partly because the entire species hibernates in only nine caves, three of those in Tennessee. “This is a species that could wink out in a few years,” Mr. Holliday said.
So he and the Nature Conservancy decided it was time to dig in, literally. They built an artificial cave, roughly 80 feet long and 16 feet wide, with 11-foot ceilings. Completed this month, and buried under four feet of earth, it lies on a slope about 100 yards from Bellamy Cave’s entrance.
The conservancy is betting $300,000 in private funds (some still to be raised) on the cave, a concrete bunker equipped with cameras and a temperature monitor. Most important, it can be scoured each spring after the bats leave, something that cannot be done in the complex ecosystem of a natural cave.
The fungus takes a while to infect a whole colony. “White nose finds its way into a cave,” Mr. Holliday said, “and by Year 3 you’ve got mass mortality.” He hopes that disinfecting the bunker will stop the fungus in its tracks. “But there’s no guarantee,” he said.
First, the bats have to come. Second, the cleaning has to work. Even at best, the bunker or others like it would be a holding action, a refuge for some thousands of bats, while scientists scramble to find another way to fight the disease or surviving bats develop some resistance to the fungus. The University of Tennessee and Southern Illinois University are collaborating with the Nature Conservancy in collecting data on bat behavior in the cave using video cameras and temperature sensors.
“What they’re doing is a fantastic project in many ways,” said Jeremy Coleman, the national white nose coordinator for the United States Fish and Wildlife Service. “But it’s a crapshoot.” Although Mr. Holliday has consulted bat experts on every aspect of the cave — from temperature to airflow to varying the texture of walls and hanging fabric with three different sizes of mesh so that bats have something to hang on to — he believes the effort is a first.
If it works, the technique could be applied to abandoned mines and other built structures where bats hibernate. And whatever happens, the bunker is equipped with cameras and temperature sensors to study bats’ behavior and see if their choice of microclimate affects their susceptibility to the fungus.
The lack of weapons to fight the disease is not surprising, since it was only in 2006 that it was first noticed. Government agencies, research scientists and conservation groups quickly turned their attention to the problem.
The first step was determining the cause of the syndrome, which appears as a fuzzy white growth on the muzzles of sick and dying bats. David Blehert and his colleagues at the United States Geological Survey identified the culprit as a previously unknown species of fungus that they called Geomyces destructans. It is a soil fungus that thrives in the cold temperatures of caves where bats hibernate.
Fungi rarely pose a problem for healthy mammals, so there are few treatments. It’s easy enough to kill a fungus with bleach, but not when it has infected an animal. Amphibians have suffered major losses recently from another fungus. But climate change and habitat loss may have contributed stress. For bats, it seems the problem is simply that the fungus was new to the United States.
The many species of bats that do not hibernate were not affected. Hibernating bats not only have a lower metabolism and body temperature, but they are also densely packed together, so the fungus can spread easily.
Evan McGlinn for The New York Times
Extracting sebum from a bat wing to study it for white nose syndrome, which has killed five million bats.
It eats holes in the delicate, translucent tissue of their wings, and drains the bats’ energy reserves. Sometimes bats fly in middle of winter when they should be hibernating. If the damage is severe enough, they cannot survive.
Evan McGlinn for The New York Times
Researchers from Boston University are trying to figure out how bats can avoid the fungus.
After the fungus was identified, it was found in Europe, where it seemed to have been living in soil in caves and infecting bats for a long time, without the terrible mortality seen here.
The evidence, said Jeff Foster, a wildlife disease ecologist at Northern Arizona University, is that there is “a lot of genetic diversity in Europe” among strains of the fungus and very little in the United States — strongly suggesting that it has been in Europe “for a very long time” and somehow made its way across the Atlantic.
Dr. Foster, who, with colleagues, has sequenced the genomes of about 30 samples of the fungus, said that while this explanation is likely, he will not consider it nailed down until the origin of the fungus in Europe is identified, which he thinks should occur in a year or so. But, he said, the major importance of full genome studies is to track how the fungus spreads in the United States. Because strains here are so similar, tracing the spread can be done only by using the tiny genetic differences that show up in comparing entire genomes.
Bat experts suspect that people who explore caves unwittingly carried the fungus to the United States from Europe, but they don’t know for sure. Many caves in the eastern part of the country — all those on public land in Tennessee, for instance — have been closed to humans, but the fungus still spreads. The pattern, says Dr. Foster, is “consistent” with bats carrying it.
Although the fungus infects European bats, it does not cause the level of damage that it does to American bats, and one hope scientists have is to learn the nature of resistance to the fungus. Do European bats have different behaviors? Are there physiological changes?
To answer some of these questions, researchers around the country are catching, inspecting and banding bats, both to learn what is going on with the populations in general and to see if survivors are breeding and producing resistant offspring.
Nets or other traps are placed at cave entrances or other places where bats are roosting. This summer, Nate Fuller of Boston University captured little brown and big brown bats as they exited a barn in Massachusetts, where they had moved after hibernation to give birth and raise their pups. He measured them, took samples of oily material on their wings, and noted scarring on wings of survivors of white nose.
In Europe, Natalia Martinkova at the Academy of Sciences of the Czech Republic is studying how bats there respond to infection from the fungus. By studying what proteins genes produce during hibernation, she hopes to understand “what genes that might be involved in the immune response.”
In the United States, researchers are pursuing many routes of study, including a project being undertaken by DeeAnn Reeder and Ken Field at Bucknell University that involves 150 little brown bats they are infecting with different doses of the fungus.
Dr. Reeder and Dr. Field will watch the progress of disease in different conditions and track immune activity with blood tests. “We don’t fully understand the nature of immunity in hibernation,” Dr. Field said.
For now, the finishing touches are being put on the Tennessee bat bunker. The mass of concrete and earth was under a baking late-summer sun during construction, and air-conditioners are needed to get the cave down to between 41 and 50 degrees by next week, when it is scheduled to be closed to humans.
Recorded calls of bats will be used to attract them to the cave. Gray bats could begin to gather in the area in prehibernation mode any time now; most will be hibernating by mid-November.
Win, lose or draw, the bet has been laid. And one cannot help think that the original Doc Holliday, known to gamble on occasion, and not one to avoid a showdown, would have approved.
The artificial cave built for bats in Tennessee has a human entrance below and a bat entrance above. In the summer, any fungus left by the bats over the winter will be cleaned up.
A man-made bat cave in Tennessee is looking for tenants. An hour northwest of Nashville, the artificial cave is built to give thousands of bats a haven from a devastating infection called white-nose syndrome.
Millions of bats in the Northeast have died from the infection since it first showed up a few years ago. The culprit is an invasive fungus that grows in caves. When bats hibernate inside, they wake up with faces covered in white fuzz and often wind up starving or freezing to death.
"It's kind of terrifying," says Ann Froschauer, communications leader on white-nose syndrome for the U.S. Fish and Wildlife Service in Massachusetts.
Since it was first found in New England six years ago, white-nose has spread, from Canada to Alabama. Froschauer witnessed firsthand one of the worst die-offs. She says the cave floor was littered with tiny bones like pine needles.
"I knew that that's not what it was, but it was just really impossible for me to understand there's ... an inch-and-a-half- to 2-inch-thick carpet of just bones on the floor here, and skulls," she says, "and if you crouch down and look, you can see there's little clumps of fur and decaying tissue."
Finding A Solution, Quickly
Scientists fear regional extinction for some species in a matter of years, leaving precious little time for a solution. Some are working on treating the infection and developing a vaccine. Biologist Cory Holliday says those approaches are valid, but hard to do on a meaningful scale.
"None of it is environmental changes to treat thousands of bats, or to help save thousands of bats," he says.
That's why Holliday's employer, The Nature Conservancy, fronted a big part of the $300,000 to hire a construction crew and fire up some earthmovers.
The concrete box buried in a hillside is almost as long as a basketball court, but only half as wide. It's high-tech inside, with surveillance cameras that detect heat without getting warm or making any noise — even ultrasonic sound could be a deal-breaker to bats moving in. To power the gear, workers screw in electric panels.
The idea is to offer bats a safe winter home, where every summer humans could go inside and clean out any lurking fungus, keeping white-nose syndrome in check.
Holliday hopes a few hundred bats will make it their home this winter, with more to follow.
"If we get the conditions right, there could be over 200,000 bats here, is what we've estimated," he says.
The clock is ticking. Holliday is hoping to lure bats over from a nearby natural cave, where early stages of white-nose were just found.
"We will be broadcasting sort of ultrasonic bat calls from around the entrance area, just hoping to draw them in," he says.
The disease often takes just a few winters to hit a kind of critical mass and ravage a sleeping population. Holliday hopes before it comes to that, the new cave can prove a viable model. He'd rather count bats in the air, than on the ground.
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In Tennessee, a cave is the winter home to 160,000 endangered gray bats that could be extinct within a decade from white nose syndrome.
"This is a wildlife disease that is unprecedented in our history," says Cory Holliday of the Nature Conservancy.
Scientists are still mystified by this fungus, which shows up as white powdery residue and disturbs the bats' natural sleeping pattern.
"Basically, it causes bats to use up energy they've stored during winter, and they come out of hibernation early -- before there is any food available and while it is still very cold -- and they don't make it through the winter," says Holliday.
"White nose" was first discovered in four caves in New York back in 2006. Now it's in 19 states and moving further west every year.
Ann Froschauer of U.S Fish and Wildlife, which coordinates the patchwork of research programs, says going into a cave where bats have died is "pretty grim."
"You're looking in and it looks like a carpet of pine needles on the floor of the cave, except that you know it's not pine needles, it's bones," she says.
Cory Holliday and the Nature Conservancy are so concerned about the Tennessee gray bat that they're taking a dramatic $300,000 gamble: building a first-of-its-kind, man-made bat cave.
"The bats will come hibernate in the winter time," he says. "After they leave in the spring, we can go in and clean the fungus out of the artificial cave."
Scientists hope that by keeping the cave clean, they'll be able to slow the spread of the disease.
"Eventually, we could easily sustain 10,000 to 20,000," Holliday says. "There's enough surface area, really, for about 200,000."
If it works, other artificial caves could be built elsewhere, which might help save hundreds of thousands o America's most endangered bats.
- Nature Conservancy
- U.S. Fish and Wildlife Service
- Bucknell University research
- Bat Conservation International
The world's first man-made cave for hibernating bats was built in August and September 2012. It provides bats a refuge from deadly white-nose syndrome.