Building a Bat Cave to Battle a Killer
By JAMES GORMAN; nytimes.com
CLARKSVILLE, Tenn. — For about six years, Cory Holliday, the Nature 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.
White Nose Syndrome impacting the northeast(in brown)
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.
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.
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.