Al Hicks was standing outside an old mine in the Adirondacks, the largest bat hibernaculum, or winter resting place, in New York State. But bats dying from a mystery illness have been found in the snow in daylight hours.
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.
“This is probably one of the strangest and most puzzling problems we have had with bats,” said Paul Cryan, a bat ecologist with the United States Geological Survey. “It’s really startling that we’ve not come up with a smoking gun yet.”
Merlin Tuttle, the president of Bat Conservation International, an education and research group in Austin, Tex., said: “So far as we can tell at this point, this may be the most serious threat to North American bats we’ve experienced in recorded history. “It definitely warrants immediate and careful attention.”
This month, Mr. Hicks took a team from the Environmental Conservation Department into the hibernaculum that has sheltered 200,000 bats in past years, mostly little brown bats (Myotis lucifugus) and federally endangered Indiana bats (Myotis sodalis), with the world’s second largest concentration of small-footed bats (Myotis leibii).
He asked that the mine location not be published, for fear that visitors could spread the syndrome or harm the bats or themselves.
Other visitors do not need directions. The day before, Mr. Hicks saw eight hawks circling the parking lot of another mine, waiting to kill and eat the bats that flew out.
In a dank galley of the mine, Mr. Hicks asked everyone to count how many out of 100 bats had white noses. About half the bats in one galley did. They would be dead by April, he said.
Mr. Hicks, who was the first person to begin studying the deaths, said more than 10 laboratories were trying to solve the mystery.
In January 2007, a cave explorer reported an unusual number of bats flying near the entrance of a cavern near Albany. In March and April, thousands of dead bats were found in three other mines and caves. In one case, half the dead or living bats had the fungus.
One cave had 15,584 bats in 2005, 6,735 in 2007 and an estimated 1,500 this winter. Another went from 1,329 bats in 2006 to 38 this winter. Some biologists fear that 250,000 bats could die this year.
Since September, when hibernation began, dead or dying bats have been found at 15 sites in New York. Most of them had been visited by people who had been at the original four sites last winter, leading researchers to suspect that humans could transmit the problem.
Details on the problem in neighboring states are sketchier. “In the Berkshires in Massachusetts, we are getting reports of dying/dead bats in areas where we do not have known bat hibernacula, so we may have more sites than we will ever be able to identify,” said Susi von Oettingen, an endangered species biologist with the United States Fish and Wildlife Service.
In Vermont, Scott Darling, a wildlife biologist with the Fish and Wildlife Department, said: “The last tally that I have is approximately 20 sites in New York, 4 in Vermont and 2 in Massachusetts. We only have estimates of the numbers of bats in the affected sites — more or less 500,000. It is impossible for us to count the dead bats, as many have flown away from the caves and died — we have over 90 reports from citizens across Vermont — as well as many are still dying.”