Inside the gaping mouth of Mammoth Cave, hibernating bats sleep in permanent twilight, each huddled in its own limestone crevice. Every fall, these big brown bats (Eptesicus fuscus) squeeze their furry bodies into nooks in the cave walls, where they enjoy protection from the bitter wind and the waterfall that sprays across the entrance. But there’s little a snoozing bat can do about a persistent scientist.
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“Just...let...go...with...your...feet,” coaxes Brooke Slack, a biologist at the Kentucky Department of Fish and Wildlife Resources, as she stands on tiptoes and reaches with gloved hands to pry a bat from the wall.
The bat, visible by the light of her headlamp, lets out a stream of tiny, infuriated shrieks, baring its sharp white teeth in protest. Slack gently loosens the bat’s claws from the rock and slips the four-inch-long animal into a brown paper bag. On this gray December afternoon, Slack and her colleague, a Northern Kentucky University microbiologist named Hazel Barton, are pressing this unlucky bat into service for its species.
Mammoth Cave, the longest known cave in the world, stretches at least 390 miles under the forests of southern Kentucky, and its twisting tunnels have fascinated explorers, scientists and tourists for well over a century. Slack and Barton have come for a different reason: the cave is a front line in the most precipitous decline of North American wildlife in living memory.
With a half-dozen grumpy bats bagged, Slack, Barton and several co-workers lug their gear to the cave’s Rotunda Room, where the limestone forms a grand domed ceiling. On summer days, this natural underground chamber is packed with tourists, but today the scientists have the place to themselves. Clad in disposable white Tyvek suits to avoid tracking microbes into or out of the cave, Slack holds each protesting bat while Barton clips samples of hair and swabs faces and wings.
“Look at you, with your dirty, dusty little face,” Barton coos, shining her helmet lamp on one screaming bat.
Barton and Slack are good friends, and they work together often even though they have different passions. Barton is interested in bats because they live in caves. Slack is interested in caves because they’re home to bats. Barton has a map of South Dakota’s Wind Cave tattooed on her arm. Slack has a tiny silhouette of a bat tattooed behind her ear.
They both know that somewhere in this cave, even on these bats, may lie spores of the fungus Geomyces destructans, which is devastating hibernating bat populations in the Northeastern United States. The fungus appears to be the cause of a disease called white-nose syndrome, which has killed more than a million bats in the past four years. It even threatens some of the continent’s most abundant bat species with extinction.
Mammoth Cave has nearly 500,000 visitors per year, any one of whom could transport spores in or out. So far, despite painstaking searches by Slack and her crew, the fungus has not been found. But the disease has been confirmed in neighboring Virginia, West Virginia and, most worrisome, in a Tennessee cave only 80 miles from Mammoth.
“Oh, look at this,” Slack says to her colleagues. They hear the note of concern in her voice, and the silence is immediate and thick. As headlamps turn toward her, Slack stretches out a bat wing, its thin membrane marked by two half-inch tears. They could be from a run-in with an owl, or a barbed-wire fence. Or they could be a sign that white-nose syndrome has crossed the state line and arrived in Mammoth.