As winter approaches and many animals prepare to enter hibernation, biologists in Maine and throughout the Northeast are gearing up once again to monitor for a bat-killing fungus that scientists fear could wipe out some bat species in the region.
Since 2006, biologists have watched with alarm as white-nose syndrome has gradually spread in bat populations in the Northeast and beyond. An estimated 1 million little brown bats — one of the most common types of bat found in New England — already have died of a disease that afflicts the animals while they hibernate.
And with no easy way to fight the fungus linked to the disease, biologists fear white-nose syndrome could decimate one of nature’s most effective forms of insect control.
“It is pretty grim. The prognosis right now is not good for bats throughout the Northeast,” said Ann Froschauer, communications leader for the U.S. Fish and Wildlife Service’s white-nose syndrome program.
Last May’s announcement that biologists had confirmed the presence of white-nose syndrome in two Maine caves where bats hibernate was no surprise. At the time, the bat-killing fungus had been found in every other New England state except Rhode Island and had been documented in the Canadian provinces that neighbor Maine.
John DePue, a biologist at the Maine Department of Inland Fisheries and Wildlife, said crews plan to conduct additional surveys of bat wintering locations — known as hibernacula — beginning in March. The two infected caves identified so far were both in Oxford County.
DePue said it is hard to tell how the disease is affecting Maine bats, other than anecdotally.
After the announcement that white-nose syndrome had been documented in Maine, DePue received calls from residents saying they were experiencing more insects and seeing fewer bats this summer. But the biologist said he also has been impressed by the number of people calling to report bats in their attics — something that his colleagues in other Northeastern states are hearing less and less.
“We do still have little brown bats living in people’s houses and attics, and to me that is encouraging,” DePue said.
As implied by its name, white-nose syndrome’s most obvious symptom is a white fungus that grows on bats’ muzzles while they hibernate. While bats hibernate, their immune system is suppressed and their body temperatures drop to almost the same temperature as the surrounding cave, making them susceptible to the fungus in the caves. Infected bats have been observed flying in daylight during winter outside of hibernacula.
One of the challenges of tracking the effects of white-nose syndrome in Maine is that, because of the state’s hard-rock geology, the Pine Tree State has relatively few caves where bats hibernate. Most of Maine’s summer and spring bat residents spend their winters elsewhere in southern New England, the northeast or eastern Canadian provinces — in other words, in areas already hard-hit by the disease.
“Most of those [areas] have been infected by white-nose syndrome,” DePue said.
Counting bats in spring and summer can be difficult because of the fact that the species found in Maine often live in small groups. This past summer, DIF&W biologists began acoustic studies that will enable biologists to gauge how many individual bats and how many species were observed during each listening session.
But DePue said it will take time to have the data analyzed. And biologists will need several years of results to glean any information about how Maine’s bat populations have been affected by the disease.
The news has not been encouraging from other states where such studies have been ongoing for several years.
Canadian researchers recording little brown bat “echolocation” calls along New York’s Hudson River during spring and summer from 2007 to 2009 reported a 78 percent decline in bat activity since the disease first appeared locally, according to a research paper published in the June 2011 edition of the journal Biology Letters.
Meanwhile, an August 2010 study published in the journal Science suggested a 99 percent probability of “regional extinction” of little brown bats within the next 15 years. With more than 1 million bat deaths reported already, the U.S. Fish and Wildlife Service is calling white-nose syndrome “the worst wildlife health crisis in memory.”
Froschauer with the U.S. Fish and Wildlife Service said once the fungus infects a site, it likely will remain infected and continue to plague bats that return there in the future.
Froschauer said researchers are exploring possible treatments for the disease. But the fungus that causes white-nose syndrome does not simply infect the bats’ exterior; it actually gets into their tissues as well. So many of the compounds effective at killing the fungus also can kill the bats.
Additionally, bats burn critical fat reserves every time they are disturbed during hibernation, to the point where several disturbances during the winter can be fatal to even healthy bats. Many treatments could require multiple applications to be effective.
“So it is much more difficult than … other fungal infections,” Froschauer said.