From The New York Times:
Al Hicks was standing outside an old mine in the Adirondacks, the largest bat hibernaculum, or winter resting place, in New York State. It was broad daylight in the middle of winter, and bats flew out of the mine about one a minute. Some had fallen to the ground where they flailed around on the snow like tiny wind-broken umbrellas, using the thumbs at the top joint of their wings to gain their balance. All would be dead by nightfall. Mr. Hicks, a mammal specialist with the state’s Environmental Conservation Department, said: “Bats don’t fly in the daytime, and bats don’t fly in the winter. Every bat you see out here is a ‘dead bat flying,’ so to speak.”
They have plenty of company. In what is one of the worst calamities to hit bat populations in the United States, on average 90 percent of the hibernating bats in four caves and mines in New York have died since last winter. Wildlife biologists fear a significant die-off in about 15 caves and mines in New York, as well as at sites in Massachusetts and Vermont. Whatever is killing the bats leaves them unusually thin and, in some cases, dotted with a white fungus. Bat experts fear that what they call White Nose Syndrome may spell doom for several species that keep insect pests under control. Researchers have yet to determine whether the bats are being killed by a virus, bacteria, toxin, environmental hazard, metabolic disorder or fungus. Some have been found with pneumonia, but that and the fungus are believed to be secondary symptoms.