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.

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. 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.

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