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WASHINGTON (Reuters) - A previously unknown fungus that thrives in chilly temperatures may be the culprit behind the deaths of at least 100,000 bats hibernating in caves in the northeastern United States, scientists said on Thursday.
The fungus is a white, powdery-looking organism found on the muzzles, ears and wings of dead and dying bats hibernating in caves in New York state, Maine, Vermont and Connecticut in the past two years, they wrote in the journal Science.
"Essentially, hibernating bats are getting moldy as they hang from their cave ceiling," David Blehert, a microbiologist with the U.S. Geological Survey who led the study, said in a telephone interview.
"It's decimating the cave-bat populations," he said.
Bats play a vital role in keeping down insect populations, pollinating plants and spreading around plant seeds.
The disease is affecting all six species of hibernating cave bats in the northeastern United States -- little brown bats, big brown bats, northern bats, tricolored bats, Indiana bats and the small-footed myotis, Blehert said.
At least 100,000 and perhaps as many as 200,000 bats have died since the so-called white-nose syndrome linked to the fungus first appeared in the winter of 2006-2007, he said.
The fungus was found to have colonized the skin of about 90 percent of the 117 bats examined after they died.
Migratory tree bats, which live in the same region but fly to warmer locales in the winter rather than hibernating in caves, have not been affected, Blehert added.
Based on bat population counts done in two caves in New York state, the disease may be killing off more than three quarters of the winged mammals as they hibernate.
The culprit may be a previously unknown species of the fungi genus Geomyces, which is present in soil and eats organic matter. The new one thrives in temperatures like those seen in caves, 36 to 59 degrees Fahrenheit (2 to 15 degrees Celsius).
The scientists said they have not yet determined whether this fungus is the only factor in the bat deaths. Most of the bats also are emaciated.
They are trying to learn whether the disease emerged because the fungus somehow was introduced into the caves, or whether it already was there and began harming bats only after the animals were weakened by some other unknown cause.
The researchers likened the threat to that posed by another fungus that causes a skin infection and is linked to large declines in amphibian populations globally.
Editing by Sandra Maler