Help Conserve Massachusetts Bats

After receiving reports in February from Vermont and New York about large numbers of bats dying in caves, biologists from MassWildlife and the U.S. Fish and Wildlife Service investigated caves and mines in western Massachusetts where colonies of bats are known to spend the winter. Biologists observed bats flying around outside of the state’s larges mine when they should have all been inside hibernating, and found dead bats near the entrance of the hibernacula (winter quarters) which were collected for further study. Biologists confirmed that these bats, like the ones in Vermont and New York, were affected with white nose syndrome (WNS), a term used to describe some of the bats found at these sites that look like their faces were dipped in powdered sugar. This white material is a fungus that is growing on the faces of up to 10% of the bats at the affected sites.   Up to 97% of the bats at some affected sites in New York have died.

Bats with crusting white fungus were first found in New York bat hibernacula during the winter of 2006-2007. Mortality was high and aroused concern among the bat conservation community. By winter 2007-2008 the syndrome and associated mortality had spread to many of the largest New York hibernacula and to sites in Vermont and Massachusetts. New sites are still being reported.  Of the eight species of bats currently found in Massachusetts, it appears that the bat species most affected by WNS include widespread and common species such as Little Brown Bats, Eastern Pipistrelles and Northern Long-eared Bats as well as the rare, state listed Small-footed Bats. These bats hibernate in caves or mines. Big Brown Bats which commonly hibernate in buildings are not yet known to be affected.  The Red Bat, Hoary Bat and Silver-haired Bat are migratory and apparently not affected.

Bats at the affected sites have exhibited some unusual behaviors. These behaviors include clusters of bats roosting in the light zone close to cave or mine entrances; dead bats or bat remains found outside of caves in the snow; nearby citizens reporting bats flying during the day in very cold weather (15-20°F) and bats roosting on exterior house walls.  Flying bats have been observed falling to the ground or crash landing and several have been found roosting in woodpiles.  Midwinter necropsies of bats have found the mammals’ fat stores completely depleted, when they would normally last until the bats emerge in spring and begin to feed on flying insects.

Wildlife managers are concerned about the outbreak because bats congregate by the thousands in caves and mines to hibernate during winter months.  If WNS is caused by an infectious agent, this behavior increases the potential that the disease will spread among hibernating bats.  In addition, hibernating bats disperse in spring and migrate, sometimes hundreds of miles away, to spend the summer.  Bats are important predators of mosquitoes and other insects. A study from Boston University estimates that 14 -15 tons of insects are consumed each summer by the 50,000 Big Brown Bats that live within the bounds of Route 128. “High bat mortality is a major concern because bats have a low reproductive rate,” says Dr. Thomas French, MassWildlife Assistant Director for Natural Heritage and Endangered Species. “Most bats raise one pup per year.  It will take decades for bat populations to rebound after a large die-off.”

Currently, scientists do not know what is causing bats to die in such great numbers. It is not clear if white nose syndrome is a cause or a symptom of bat mortality. Currently, there are 9 universities, 4 or 5 federal agencies, state wildlife agencies and health departments from 3 states, and a host of other volunteers, researchers, and cavers working together to gather data, understand this condition and to diagnose the cause.