Bats in Pennsylvania are leaving their caves after a season of hibernation, but their colonies are much diminished. Scientists say white nose syndrome has caused a massive number of deaths in Western Pennsylvania hibernacula for the first time this winter.

"Last year we had the fungus there," said Greg Turner, endangered mammal specialist with the Pennsylvania Game Commission. "This year we had mortalities starting at those sites and some neighboring sites, and we were able to confirm it across a much larger geographic area."

Turner said of the two sites he monitored, he guesses mortality rates to be about 70 to 80 percent. About 90 percent of affected populations along the East Coast have died.

White nose syndrome is characterized by white fuzz that develops on the ears, nose and wings of hibernating bats. Scientists still don't know exactly how bats are dying, but the illness strikes and may be spread during hibernation. This winter was an important one for research in Pennsylvania.

DeeAnn Reeder, a biologist at Bucknell University and leading white nose syndrome researcher, ran experiments trying to determine exactly why bats are dying, and looking into possible preventive measures.

She and colleagues ran an experiment in a mine shaft near Allentown to see if anything could prevent the growth of the fungus. They built mesh cages and put bottles of different compounds underneath, with the idea that the evaporating liquids might protect the bats in the cages above.

Instead, the cages made the bats a target for a different threat: raccoons.

"It was an incredibly disheartening day," Reeder said. "When we got in there, we went to the first cage and saw that it had been ripped open and all the bats were gone. My heart sank and I was pretty sure we would find all the other cages in the same condition, and, in fact, we did."

Turner said the team did not expect raccoons to descend that far underground. What's worse, of the 3,000 to 4,000 bats that were alive in the cave last fall, fewer than 200 were left this spring.

Cases of the mysterious disease were confirmed for the first time in Indiana, North Carolina and Kentucky this winter.

Reeder, Turner and others from around the country will meet in Arkansas next month to share research from experiments conducted during this winter's hibernation.