One by one, they slide a dozen feet down the dirt embankment on the inside and cautiously stand as their eyes adjust to the yellowish light cast by their headlamps. The experienced cavers who have accompanied them have cautioned: Don’t let your helmet knock the stone overhead. Don’t touch the walls or stumble against them. Some of the partially detached stone slabs—as large as a dining room table—that surround the visitors appear to be hanging from the walls and ceilings at crazy angles. This was an active mine a century ago, and manmade tunnels and underground rooms are far less stable than those carved by nature. No one wants to find out what it would take to make one of the overhanging slabs break free.

The cave is in Schoharie County, but it looks like another planet, with walls and ceilings of gunmetal-colored rock glimmering with a metallic sheen. The reflective appearance of the stone comes from bacteria that grow on the rock surfaces in this damp, cool underworld and pick up the headlamp light with a silver, gold or blue color, depending on which variety they are.

In some places, the ceiling buckles so low that you have to hunch your shoulders and drop your head. Underfoot, it looks like the floor has fallen through. Broken slabs of stone lie where they dropped, creating little crevasses that collect water and are, on this late winter’s day, patched over with dirty ice. Upside-down icicles grow from the rock floor of the cave, their pointed ends reaching toward the ceiling. They form when the constant drip from above begins to freeze, and repeated drops hitting the same spot build up into slender columns of ice two and three feet high.

This cave is one of many where several of the nine bat species found in New York state spend the winter, and bats are what these explorers are seeking. The kind of winter sleep that bats normally experience is often described as “hibernation,” but it is not the same deep, unresponsive state that turtles and frogs enter into in the fall, and which lasts unbroken until spring. When bats “hibernate,” they go for long stretches without moving, but they can be awakened and they will briefly move around and even open their wings if disturbed.

In a normal winter, the bats would quickly go back to sleep if disturbed. They would continue to live off of stored body fat that they had packed on in the fall from their diet of insects. And in a normal winter, without the daily demands on their energy that flying requires, the bats would survive until spring on that stored fat, until they left the cave and the insects returned.

But the past few years in New York have not been normal for bats. Hundreds of thousands of them have died in the throes of a mysterious illness that has drained the fat from their bodies in midwinter and has driven them from their normal winter sleep into the kind of activity and hunger that they should not experience until April.

Emaciated and famished, the bats have left their snug caves and flown outside into an upstate winter. And there in the open they have plummeted to the ground and died, often leaving pathetic trails behind them in the snow as they struggled to crawl away. The ravens and crows have had rich pickings at the mouths of these caves. Often, biologists find only a few dark flecks in the snow to mark where the bats died.

Most of the dead bats have had one common symptom: A fungus has grown over their face, obscuring their features with an off-white fuzz, like the cover of a used tennis ball. And so scientists have given the bat deaths the name “White-Nose Syndrome.”

The Capital Region is the epicenter for this disease, which has so far stymied researchers in several countries as they work overtime to find a way to stop it. White-Nose Syndrome started in Schoharie County and has since spread to eight other states. Although scientists know the broad general scientific group that the fungus belongs to, no one has yet been able to identify the exact species, says Jeremy Coleman, a biologist with the U.S. Fish and Wildlife Service in Cortland who is coordinating the national response.

Al Hicks, the mammal specialist for the state Department of Environmental Conservation’s Endangered Species Unit, fears that some bat species risk dying off altogether. White-Nose Syndrome has hit some species particularly hard—one is the Little Brown Bat, best known to homeowners as the bat most likely to blunder inside on a summer night—and some hardly or not at all, including the Big Brown Bat and some species that migrate to Southern states in the winter instead of hibernating.

The disease is not only bad news for the bats. Bats are often reviled and misunderstood, but they are actually very beneficial animals that consume enormous numbers of insects. Humans who understand bats are justifiably both frightened and saddened at the ferocity with which White-Nose Syndrome has devastated New York’s bat population.

“At the rate it’s spreading, at the rate it’s killing the bats,” Hicks says, “we will potentially lose species within a few years.”

Al Hicks spends a lot of time in caves, surveying the bat population, and he has gotten to know many of the people in the Capital Region who go caving as a hobby. This day’s expedition starts with a hurried conference with three cavers in the parking lot of a convenience store to discuss strategy and location. The cavers include Joe Armstrong, who is a housepainter by day, and Eliah Kagan and Kevin Pieluszczak, both students at Syracuse University and members of the college outing club.

“We’re trying to get the local caving community involved in these surveys, because there’s a lot of them, and not a lot of us,” Hicks explains as the group sets out again in separate trucks. “And Joe knows his bats very well. The caving community has been very good; they’ve helped us since 1980, when we first started doing this. We’ve never done any big site without them.”

The three cavers, for their part, are trying to keep curiosity seekers out of the caves, so as to avoid disturbing the bats, and also to keep people who know nothing about caving from going into these old mines and natural caverns. In keeping with their request, the caves that Hicks will go into this day will not be identified.

Unbeknownst to this group, the U.S. Fish and Wildlife Service will soon ask even experienced cavers to curtail their underground explorations. White-Nose Syndrome is believed to spread from bat to bat in infected caves, but it’s also been found in caves long distances apart, prompting federal wildlife authorities to suspect that humans may play a role in the transmission, even though humans do not catch the disease.

“We suspect that White-Nose Syndrome may be transmitted by humans inadvertently carrying White-Nose Syndrome from cave to cave where bats hibernate,” U.S. Fish and Wildlife Director Marvin Moriarity said in a release issued on March 26.

The agency is asking cavers to use only clothing and gear that has never been in affected states, and to avoid caves in the winter altogether. But in the end, Fish and Wildlife can only appeal to the sense of responsibility that prevails in the caving community—careless cavers don’t have long careers—because there are hundreds of caves in the Northeast, and it would be impossible to police them or limit access to them.

The warning to cavers comes as the rapid die-off of bats is shocking researchers.

“Over two years, mortality rates have ranged anywhere from 80 to 90 to 97 percent,” Hicks says. Caves in the Capital Region that once would have held thousands of hibernating bats now have only a handful. As of this writing, Hicks was still tallying the winter bat survey, but said that “it’s clear that numbers are continuing to decline throughout the state. Some places are declining dramatically.”

One cave in Ulster County that had 10,000 hibernating bats two years ago contained slightly more than 100 bats this winter, Hicks says.

In addition to the visible fungus, most of the dead and dying bats are emaciated. One question researchers are trying to answer now is whether the bats are entering hibernation at the proper weight, or if for some reason they aren’t able to prepare properly for hibernation in the fall.

An early hope that the bats that did not die last year in affected caves might have some natural genetic immunity to the disease is proving false, says Jeremy Coleman at U.S. Fish and Wildlife.

Now, Coleman says, it appears that “the survivors from last year were just lucky.” And for many of those initial survivors, their luck ran out this winter.

Inside the cave, Hicks or ganizes the group into a line that searches the cave in a circular pattern. The interior of the cave is like an enormous open room with passages leading off in several directions. Bats sometimes hang from rock faces or ceilings in plain sight, but they also sometimes crawl into tiny cracks. As the group moves around, a few bats can be seen.

Hicks inspects those that he can see clearly without disturbing; so far, all appear to be healthy. Just a little more than two years ago, a day like this would have been an enjoyable trip in the field, and Hicks might have seen hundreds or even thousands of bats in a cave, instead of a few dozen.

In January 2007, a man exploring a cave in the hilltowns of western Albany County noticed bats in the cave clustered near the entrance. When the DEC heard about the unusual sighting—bats normally would be deep in the caves at that time of year—the agency asked another caver to verify the report. Around the same time, Hicks and the State Health Department started hearing odd reports of bats flying around in the winter. Then in March, some DEC biologists conducting a bat survey at a cave in Albany County made a hideous discovery.

“They called me from the site and said, ‘There’s thousands of dead bats,’ ” Hicks recalls. He examined the photographs the biologists brought back, and started sending them to bat researchers around the country.

“It was absolutely clear to me that this was something new,” Hicks says. “Nobody had ever seen anything like it before.”

In February 2008, a caver contacted Hicks to show him some photographs of bats he had taken in a cave in Schoharie County in January 2006. Because of the close connection between cavers and bat biologists, word of the strange bat disease was circulating in the caving community, and the man had reviewed his earlier photographs. One of the bats in his photos had the fungus, something the man had not recognized at the time. Hicks now had a confirmed sighting dating to 2006, and confirmation of the disease in separate counties, at locations many miles apart.

One theory on White-Nose Syndrome suggests that it is an introduced pathogen, possibly brought into a cave on the boot of a traveler from another part of the world. Introduced pathogens have gotten a lot of attention in recent years, because as international air travel and cargo shipping have reached into ever more remote parts of the globe, the potential for a new disease to make the return trip has increased.

“This has never been observed in North America,” Hicks says. “We don’t know what it is. It seems very clear that it is a pathogen, and the only suspect is the fungus.”

“I think the only reason it’s affecting bats is because bats hibernate, so in that sense it’s not a ‘disease’ in the normal sense of the world,” he adds. “All it has to do is disrupt their hibernating cycles in some way, and they use up their fat reserves and die. It’s taken these species millions of years to evolve this habit of eating insects in the fall, and you throw something in the mix and they’ll be in trouble—and they’re in big trouble.”

Some researchers, including Ward Stone, the state wildlife pathologist, think that global warming may play a role in White-Nose Syndrome. As Stone notes, climate change has been connected to other animal deaths in New York. West Nile Virus, a mosquito-born disease of Africa that can be fatal to humans and birds, is one recent example: The first time it was found in North America was in New York City, a decade ago. Stone was instrumental in helping to identify West Nile in dead birds.

The summers of 2006 and 2007 were unusually dry in New York, Stone notes, and many of the insects that bats eat require ample water during their development. Whether the fungus that causes White-nose Syndrome was already present and just needed the right combination of factors to overwhelm the bats, or whether it was introduced, it may be that the bats—already feeling the effects of an inadequate food supply—were more susceptible than they might normally have been.

“There’s no reason to think that bats haven’t faced fungal infections before in hundreds of thousands of years, even millions of years,” Stone says. “So much movement of humans and goods could help a fungus move, and to places it hasn’t been before.”

In his lab at the Five Rivers Wildlife Resources Center in Delmar, Stone is supervising the preparation of cultures of the fungus in an effort to learn more about the conditions under which it grows. Two Cobleskill College student interns, Sami Kadhim and Joseph Hoyt, have been working with Stone on the culturing project, and the list of what the fungus grows on seems endless: wood, lichens, grass clippings, dead spiders, sheep’s blood, mushrooms, bird seed, banana slices, corn husks. It is a cold-loving fungus that grows well in temperatures ranging from the 40s to the 50s—about the same as a refrigerator—and “it will grow on just about anything,” Stone says.

“One thing it did not grow on is Stewart’s bread—we tried wheat, we tried white,” Stone says. That’s because many commercially produced breads contain a synthetic additive to inhibit mold. Additional tests conducted in the pathology lab indicate that some common household cleaners, including Lysol, and a disinfectant used in hospitals kill the fungus.

Stone has also discovered that a bacterium known as “Pseudomonas Fluorescens” at least inhibits the growth of the fungus. One of the students cultured the fairly common bacterium from the fur of a dead Big Brown Bat found hanging on a building on downtown Albany’s Broadway this winter.

These findings—agents that kill the fungus; bacteria that interrupt its growth—provide useful information in the all-out effort to control White-Nose Syndrome, Stone says, but they do not necessarily mean that researchers are going to find a cure anytime soon. Still, he is optimistic about the progress that has been made so far, and impressed by the cooperative effort among researchers from different states and even different continents.

“There’s hundreds of people now involved in doing the research,” Stone says. “We’re rapidly gaining ground on this. We’ve got a lot at stake, but the bats have more.”

The possibility that something already naturally present in the environment such as the bacterium cultured in Stone’s research is of great interest, Hicks says. If a treatment could ever be developed, it might be applied to the bats by misting the entrances of certain caves in the fall.

“Conceptually, I think that’s one of the best chances we have that we find something out there in the environment that kills this fungus,” Hicks says. “I think that will have to be the avenue we have to take if we’re going to beat this: Find something out there that can out-compete the fungus.”

In the cave in Schoharie County, there is ample evidence of coming and going. The remnants of a campfire can be seen in one secluded corner, where people evidently sat and talked and drank. A small songbird, the Eastern Phoebe, likes to nest in caves, just near the entrances; it attaches its cup-shaped nest of mud and plant fibers to a small niche in the wall, and several Phoebe’s nests can be seen in this cave. They are vacant in the late winter, but they evoke the springtime image of parent birds coming and going, swooping in and out of the caves and possibly helping to spread the fungus.

Hicks finds one very sick bat in this cave; it is a Tri-Colored Bat, and its face is covered with fungus. Hicks removes the bat, kills it instantly by breaking its neck, and then seals it in a bag.

“He was about as sick as he could get,” Hicks says, examining the specimen.

Hicks and the cavers soon head out of the old limestone mine and travel a short distance to another cave in Schoharie County. The entrance here is wide enough to walk into, and a tunnel with a stream running through it disappears down into the darkness. A few minutes into the tunnel, the water is suddenly knee deep with runoff from recent heavy rains, and wading through this forceful stream is an unnerving sensation when the only way out is the receding square of daylight now far behind the group.

A little farther down the tunnel, the walls narrow and the ceiling becomes much lower, so that everyone has to duck their heads and hunch over for next 100 feet. Hicks has been in much tighter spaces in caves; he recalls one time when he had to squeeze through an hourglass-shaped opening in a cave so narrow in the middle that he felt the rock sides pressing on his ribs.

Then the tunnel opens up into a space like an underground church, with soaring ceilings and rounded, curved walls. Bats can be seen clinging here and there on the walls and the ceiling, and one of them—in a barely accessible portion of the wall above a rock shelf—looks like it has the fungus. Hicks climbs the shelf, balances carefully on the narrow space as the cavers spot him, and removes the bat from the wall. The bat slowly wakes up and stretches its wings. A closer examination reveals that this bat is not sick—at least, not visibly so—it’s simply got some dirt on its fur that at first looked like the powdery smudge of fungus.

In a morning that hasn’t had a lot of good news, this is one small bright spot. Hicks gently replaces the barely awake bat back on its roosting spot, and heads back into the tunnel, back toward daylight.