Winter bat die-off remains a mystery

With survivors of the area’s ravaged bat population poised to emerge from hibernation, biologists ar
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With survivors of the area’s ravaged bat population poised to emerge from hibernation, biologists are still trying to find out what caused a mass die-off this winter.

An affliction dubbed “white-nose syndrome” for the specks of fungus found around many of the dead bats’ snouts has decimated hibernation caves in eastern New York, Vermont, Massachusetts and Connecticut. Bats with white nose essentially burn through their fat stores before spring. Many fluttered out of caves this winter in a doomed search for food.

White nose has been detected in about 20 caves in the Northeast, compared to just four caves clustered west of Albany the winter before. Wildlife biologists caution that death counts are hard to estimate accurately, but they say they would not be surprised if more than 100,000 bats died this winter.

“The mortality has been substantial,” said Alan Hicks, a wildlife biologist with the New York Department of Environmental Conservation.

Hicks this winter tapped top research labs around the country to help find the cause. But pathologists have not found any evidence of an underlying virus or bacteria (the white-nose fungus is believed to be a symptom of the affliction, not the cause).

Some researchers suspect mild winters may be forcing bats to burn through their stores faster. Others fear that increased pesticide use in recent years to combat West Nile virus might be interfering with the bats’ metabolism — or killing off their insect food supply.

A number of biologists think it might be a combination of factors.

“Now it’s not a single smoking gun, you’ve got to look at the possibility of a combination of factors,” said Vermont Fish and Wildlife biologist Scott Darling.

Despite some similarities, there is no known link between the bat die-offs and the mystery affliction killing honeybees. But Barbara French of Bat Conservation International noted that some bat researchers are concerned about a new class of pesticides modeled after nicotine, chemicals which also have been mentioned as a possible culprit in the bees’ “colony collapse disorder.”

As bats in this region emerge from caves later this month in search of insects, researchers will continue to test samples and look for clues. They will also weigh some bats as they emerge from hibernation and then again this fall as they head back into caves. Biologists are particularly interested in finding out if bats are beginning their winters underweight.

And scientists will try to answer a number of pressing questions. Why are some bat species, especially little browns, harder hit than others? How can white nose ravage one cave yet leave one nearby relatively unscathed?

And most urgently: Will enough bats emerge this spring to maintain viable long-term populations?

“Are we just going to see a lot less bats on the landscape now, for a long time?” asked Susi von Oettingen of the U.S. Fish and Wildlife Service. “I don’t know.”

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