Flying in the Dark

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More than a million bats in the eastern United States are estimated to have died since white-nose syndrome was first detected in 2006.

by Madeline Bodin

© Michael Durham/Minden Pictures

© Michael Durham/Minden Pictures
Fresh snow covered the ground on a cold day last March as Marvin Moriarty trudged up the short, steep hill to the entrance of the Greeley Mine in Stockbridge, Vermont, to see first-hand the effects of white-nose syndrome in bats.

As regional director of the U.S. Fish and Wildlife Service’s northeast region, Moriarty had already seen the pictures of bats with fuzzy white fungus mustaches and knew about the ever-widening circle of affected caves in his region, starting with New York, Vermont, Massachusetts and New Hampshire in 2006 then expanding to New Jersey, Pennsylvania, Virginia and West Virginia. This spring it was confirmed in Maryland, Tennessee, Missouri, Oklahoma and the Canadian provinces of Quebec and Ontario.

Moriarty knew that thousands of bats had once hibernated in this mine and that it had been stricken with white-nose syndrome the year before. But as he and other members’ of his group donned white Tyvek cover-alls—to protect the bats, not themselves—and limboed through the bars of a gate that blocks people but lets bats pass freely into the mine, he wondered what he would find.

At first, they found nothing. Moriarty had expected to see bats lining the cave’s ceiling, but the group looked for 10 minutes before they found a bat. “The few bats that I saw did not have that classic fuzz on their noses,” he says. “They were nailed to the side of the cave with the mycelium of the fungus attaching them to the cave wall. It was on their abdomens, on their wings, it was everywhere.”

What Jonathan Wood, secretary of the Vermont Agency of Natural Resources remembers most is the pile of tiny, toothpick-like bat bones. Trained as a forester, Wood knew bones like that don’t last long in the wild. This was a fresh tragedy. As much as he knew about white-nose syndrome before visiting the mine, “It doesn’t sink home until you see the results right there in front of you,” Wood says.

They counted about 30 bats in the cave that day, but, Moriarty reports, that given their condition, none of those bats were likely to survive. “It was a powerful experience to see what a vibrant, living cave could turn in to,” Moriarty says. “It’s one of those things I don’t think I’ll forget for a long time.”

More than a million bats in the eastern United States are estimated to have died since white-nose syndrome was first detected in 2006. “White-nose syndrome is causing one of the most precipitous wildlife declines in North America in the last century,” says Nina Fascione, former vice-president for field conservation programs at Defenders of Wildlife. “I can’t overstate how huge it is. There will be significant environmental and economic consequences.”

Every bat eats up to half its body weight in insects each night. The loss of a million bats means that billions of flying insects—mostly moths and beetles, but also mosquitoes—have gone uneaten. Some of those moths and beetles are crop pests, meaning that farmers will have to use more pesticides or grow less food. As the syndrome spreads south, entire bat species are at risk of extinction. Scientists are racing to unravel the details to better understand how and where the syndrome may spread and to take action to slow it.

While the white fungus is the most obvious symptom of the syndrome, scientists have been careful not to assume it is the cause. However, in examining samples from affected bats in the low brick building that houses the U.S. Geological Survey’s National Wildlife Health Center in Madison, Wisconsin, a pattern emerged.

After analyzing more than 100 bats, microbiologist David Blehert noticed that 10 of the affected bats from different caves in different states each had the same unusual, unknown fungus growing in their skin. Further tests showed that the fungus was found everywhere white-nose syndrome was found, but not where the syndrome wasn’t present.

It’s very unusual for a fungal infection to make a warm-blooded animal sick, Blehert says. Fungi that live on the skin of warm-blooded animals are called dermatophytes. A typical dermatophyte is athlete’s foot. Generally these fungi stay in the top-most layer of skin, and while itchy, rarely kill their hosts.

The fungus Blehert discovered, however, is different. It grows right through the dead skin cells of the epidermis into the living cells of the dermis below. Further, this fungus loves the cold. It grows best in temperatures between about 41 to 50 degrees F and doesn’t grow at all at temperatures above 70 degrees. This fungus would never grow on human skin. It’s too warm. But, Blehert notes, during hibernation, bats’ body temperatures drop to within a degree or two of the temperature of the cave they are hibernating in, a temperature range that brings them within the fungi’s growth range.

Most, but not all, scientists studying white-nose syndrome agree, but Blehert is convinced that the fungus he discovered is not only the most obvious symptom of the syndrome, but also its cause. He is curious where the fungus came from and has reports of a similar fungus on bats in Europe, although that fungus does not appear to be fatal. Are North American bats merely more susceptible to the same fungus? Tests are underway to find out.

Blehert says the fungus he believes causes white-nose syndrome has the potential to spread to wherever bats lower their body temperatures in hibernation. That means scientists fear for the huge bat hibernation caves in Kentucky and Tennessee where a million or more bats may hibernate in a single cave.

One subspecies of bat is already in great peril of extinction. Just 15,000 Virginia long-eared bats hibernate in a handful of caves in Virginia, West Virginia, Kentucky and North Carolina. Because there are so few of them, the species is on the federal endangered species list. Last winter white-nose syndrome was discovered in one of the Virginia big-eared bats’ hibernation caves.

An attempt to raise 40 Virginia big-eared bats at the Smithsonian Institution National Zoo Conservation and Research Center in Front Royal, Virginia last winter, succeeded only in giving scientists valuable information about how to care for the species in captivity. Most of the bats died from stress or infections unrelated to white-nose syndrome. “We are saddened by the way things have gone,” says Luis Padilla, the center’s veterinarian. However, “we have learned some techniques that will be helpful in keeping this type of bat in a captive colony in the future.”

Other last-ditch efforts being evaluated by scientists include installing a solar-powered warming box in a cave, disinfecting a cave with a fungicide and having wildlife rehabilitators nurse sick bats back to health. In each case, the hitch is that millions of bats could be affected by white-nose syndrome, and most of those bats hibernate in inaccessible caves. “It’s enough of a crisis that we sure shouldn’t rule anything out when looking for solutions,” says Fascione.

So the scientists continue their research. At Vermont’s Greeley Mine, they want to see what will happen when rescued or rehabilitated bats are released back into the wild. Will the bats fly back to the nose-stricken caves the bats once hibernated in and can they catch the syndrome from the cave itself?

Last fall scientists gathered outside Greeley Mine in the evening’s waning light. Two scientists had just returned from a 27-hour drive to the northwest corner of Wisconsin and back. They had retrieved 80 little brown bats from a mine that has long been studied by the Wisconsin Department of Natural Resources and is known to provide a hibernation site to a robust population of bats, free of white-nose syndrome.

The bleary-eyed scientists drove through the day and night to get the bats to Vermont as quickly as possible, while the bats rode in four large white coolers stocked with icepacks to mimic the temperature, if not the ambiance, of the Wisconsin and Vermont mines. Each bat traveled inside a new, white tube sock, which, hung from the lid of the cooler, giving it something to cling to and preventing it from flying away when they opened the cooler.

Three sets of screens at the mine’s entrance prevented local bats from entering and the Wisconsin bats from leaving. The seams of the screening were further sealed with quick-hardening insulation foam. “We chose this site because there was an alternative nearby,” says Vermont bat biologist Scott Darling. Any bats returning to the Greeley Mine site would have a similar mine just yards away on the hillside.

How white-nose syndrome gets from bat to bat, from cave to cave and from region to region is still largely a mystery. By taking healthy bats from a region of the country where white-nose syndrome is unknown and having them hibernate in a mine that was affected by white-nose syndrome, the scientists hope to learn the role of the hibernation environment in the syndrome’s transmission. “We think it’s primarily a bat-to-bat fungus but we don’t know. That’s why we are doing this experiment,” Darling says.

Deep inside the cave, two scientists removed half of the bats from the socks and placed the bats’ feet against the cave wall. Most of these bats, not waking from their torpor, clung to the mine wall. Others needed coaxing to settle into their new home. Two more scientists guarded the flaps in the two inner screens so no bats could fly from the cave.

“We cannot let these bats go,” says Darling, holding the outermost screen closed. While the chance is slight that an escaped bat could somehow fly more than 1,000 miles back to Wisconsin and infect the bats there with white-nose syndrome, the scientists were not taking any chances.

The work at Greeley Cave is just one of many white-nose syndrome research projects attempting to further unravel the syndrome’s mysteries. Other scientists are testing fungicides that might rid a cave of the white-nose syndrome fungus without harming other life in the cave, creating video tapes of bats in an affected cave to study their behavior, studying bats’ genetic susceptibility to the syndrome, and investigating ways to decontaminate caving gear, such as ropes, so that white-nose syndrome isn’t spread from cave to cave.

Darling and the other scientists left two of the team behind to seal the three-screen portals with innumerable staples. They hiked down the short, steep hill in darkness. The scientists would repeat everything they had done at Greeley Mine with the remaining 40 bats at another cave several miles away and were eager to get on their way. Their plan is to return this spring. The results of the experiment will guide efforts to curb white-nose syndrome and aid the bats’ recovery. The future of the most common bat species in the East, and some of the rarest, depends on the work of scientists like these. And that night, the exhausted scientists could only trudge on. There was still work to be done.

Madeline Bodin writes from Vermont and specializes in natural sciences.

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