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See more photos in this audio slideshow with the bat biologists talking about their work!
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By Madeline Bodin
Turning his truck off the highway, Scott Darling sees the signs everywhere. In broad daylight, bats skim a recently thawed pond, and they flutter about in the roadway to the trailhead. They should still be hibernating — it is early spring, and there are no flying insects around for the bats to eat. Something is wrong.
The bats at The Nature Conservancy’s Mount Aeolus cave in Dorset, Vermont, are dying, and no one knows why. As the Vermont Fish and Wildlife Department’s bat biologist, Darling was the one who discovered a few months earlier that white nose syndrome, a mysterious ailment of bats, had struck here at New England’s largest bat hibernation site.
White nose syndrome gets its name from the white fungus that grows around the muzzle of many affected bats, making them appear as though they have rooted around in confectioner’s sugar. But not all bats have fungus on their muzzles. Some have it on their ears, forearms or wings. Others show no fungus at all.
Darling’s plan for this April day is to hike to the cave to trap and weigh 200 bats. Laboratory tests show that bats afflicted with white nose syndrome have little or no body fat. For whatever reason, they are starving to death. Darling hopes to see how well the bats survived the ravages of the syndrome over the winter.
Every time he visited the cave over the preceding months, the situation looked increasingly dire. Each trek revealed dozens more dead bats and even greater numbers that were dying. With the onset of spring, Darling is not sure what he’ll find. “All we need is one healthy bat,” he says to his three technicians as he hoists his backpack for the mile-long trek up the snow-covered trail to the cave.
Six species of bats are known to hibernate in the Mount Aeolus (e-OH-lis) cave, including the endangered Indiana bat. By far the most prevalent are little brown bats, tiny creatures weighing about 7 grams (as much as three pennies) that can live 20 to 30 years and produce just one pup each year. While many people think of bats as flying mice, they are more closely related to primates.
The mouth of the cave is set in a wall of weathered limestone. Ferns and small trees growing on the cliff ledges give the place the look of a garden grotto. This spring it is a macabre garden, however.
Two hawks wheel above the cave entrance, ready to scoop up addled bats that swoop in and out of the cave. Ravens clack and grawk just out of sight, likely scared away from scavenging bat carcasses by the arrival of Darling and his team.
What look like clumps of brown moss in the crevices around the cave mouth are actually clusters of bats. Scientists believe that as the bats starve, they move closer to cave entrances, where, during the winter months, it is colder than in the deep recesses of the cave, where they usually hibernate and where the temperature is steady. It is perhaps an attempt to save energy by lowering their body temperatures further than is the norm for their winter torpor.
Some, like these at the Aeolus cave, take their chances outside, where temperatures are colder. Whether they move near the cave mouth or outside, it’s a gamble that most bats lose. They continue to starve, if they don’t freeze to death first.
As the team sets up the harp trap that will capture the bats with nylon filaments that their radarlike echolocation can’t detect, a bat flies out of the cave and crashes into the snow nearby. Shivering, it crawls stiffly across the snow on feet and thumbs, like an ape. As it inches across the snow, Darling scoops it up and hangs it by its toes on the cliff wall at the mouth of the cave.
Bats collected at Aeolus and the information Darling and his team gather are providing insight for scientists investigating the cause of the syndrome. About 25 laboratories and government agencies are in on the research. Several are investigating infectious agents such as fungus, bacteria and viruses. Others are examining the bats’ food supply, weight and fat composition. Some labs are studying environmental contaminants like mercury and pesticides. Still others are looking into whether the bats are rousing too often during hibernation.
Aeolus has provided clues for nearly every aspect of the ongoing research on white nose syndrome. And right now, clues are about all researchers have to go on.
Nature picture credits: Photos © Landon Nordeman
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