Bats are dying at an alarming rate in the Northeast, and wildlife biologists fear the outbreak could lead to the extinction of the already endangered Indiana bat.
A typical bat cave during winter months is dark, quiet and smells faintly of guano. The winged mammals are usually found hanging upside down in a state of torpor, the decreased physiological activity of hibernation. Some hibernate alone; some in clusters.
But an epidemic has swept through bat populations in the northeastern United States, disrupting the lives of the wintering cave bats. And scientists are puzzled as to what is causing it.
The so-called “white-nose syndrome” has ravaged bat colonies in Vermont, Massachusetts and New York, leading to deaths in large swaths of the region. In caves where bats normally spend the winter hibernating, biologists are finding them emaciated and awake, or lying dead in the snow. Some have a coat of white fungus blanketing their nose and other parts of their bodies.
Bats have been spotted flying around in greater numbers than is normal for this time of year. Scientists suspect they may be starving and searching for food in a desperate attempt to survive.
Of the roughly 500,000 bats hibernating in the caves affected by the syndrome, Scott Darling, a bat biologist with the Vermont Fish and Wildlife Department, estimates that the fatality rate has exceeded 90 percent. And he fears the toll is rising.
“At this time, biologists are not optimistic that we won’t lose all of those 500,000 bats,” he said.
The cause of the deaths is unknown. Nearly all of the bats are noticeably gaunt, with extremely low fat reserves. But pathologists have found no indications of any known infection, bacteria or virus that would help pinpoint a cause. And the name, white-nose syndrome, could be misleading, as only a portion of the bats have the white fungus.
Susi von Oettingen, an endangered species biologist with the U.S. Fish and Wildlife Service, suspects the cause may be a complex interplay of factors.
“It may be environmental,” she said. “It may be a combination of something environmental and a pathogen the bats encountered in the fall. We’re looking at everything and letting our imaginations run wild.”
Scattered across the country, scientists in 10 different labs are trying to target the source of the epidemic. When a deceased bat arrives at the lab, pathologists inspect its ears, nose, eyes, wings and fur. Then they slice open the carcass, inspect the organs and collect tissue samples for testing.
Scientists also take cultures of bacteria, examine fungus found on the bats and test for rabies, said Kimberli Miller, a wildlife disease specialist with the USGS National Wildlife Health Center. “We’ve been looking at parasites, and we’ve been examining the tissues microscopically. But so far, it’s not coming together neatly.”
Among those threatened is the Indiana bat, which is already on the federal list of endangered species.
“If we lose the Indiana bat, we’re losing a species from the Northeast,” von Oettingen said. “The whole species may be gone. To me, that’s almost incomprehensible that on our watch, we’d lose a species.”
But Darling considered the little brown bat an even greater concern, since they make up a much larger portion of the bat population. About 22,500 of the 23,000 bats in Vermont’s Aeolus Cave, for example, are little brown bats.
Bats are chowhounds, capable of consuming as many as 1,000 insects in an hour — and biologists predict that this year’s die-off will cause insect populations to swell.
“When you do the math and you figure the bats might be feeding five to six hours a night — that can add up to an awful lot of insects,” Darling said.
He points to caterpillars in particular, which eat leaves and farm crops. Bats also eat beetles, flies and mosquitoes, and are believed to play a vital role in controlling outbreaks of these insects.
“We may be living in an ecological experiment that will demonstrate the role of bats,” Darling said.