CHESTER, Mass. -- A mysterious bat ailment is leaving dead bats on the ground outside caves in the Berkshires.

The Berkshire Eagle reported the illness, dubbed “white nose syndrome,” for the white powdery fungus it creates on the bats’ noses, has already killed thousands of bats in Vermont and New York.

Tom French, assistant director of the endangered species program at the Massachusetts Division of Fisheries and Wildlife, has seen the ailment’s effects first-hand in the Berkshires.

He said he found bats flying in and out of caves in broad daylight.

"They shouldn't be out of their caves during the daytime, and especially during the cold winter months," he said.

Tests show the bats’ fat reserves are depleted much earlier in the year than usual.

"This is unprecedented," French said. "International scientists have never seen anything like this before."

French said Massachusetts has a winter bat population of about 12,000 bats, with about 1,000 of those in Berkshire County.

The condition was first discovered in January 2007 in a cave near Albany, N.Y.