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Bat Mortality in Massachusetts

 

Bat mortality rates in Massachusetts caves and mines are at an alarmingly high level. Surveys in Massachusetts caves and mines conducted by biologists from the Division of Fisheries and Wildlife (MassWildlife) and the U.S. Fish and Wildlife Service in February and March of 2009 have shown dramatic rates of mortality; perhaps as high as 95 or 100 percent. The state's largest hibernacula located in Chester normally contains 8,000-10,000 hibernating bats in winter, but over the past two winters, apparently all bats have died. Biologists are attributing this die-off to White-Nose Syndrome (WNS), a white, crusting fungus on their muzzles and other parts of their body. Rowe Cave

Bats with the 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. In the winter of 2008-2009 WNS was found in bats throughout the Northeast and in caves as far south as Virginia and West Virginia.

Although the reasons are not well understood, bats with WNS deplete their winter fat reserves too quickly by the middle of winter. The affected bats exhibit unusual behavior, often moving to cold parts of the hibernacula, leaving the cave or mine during the day and during cold winter weather in an attempt to find food during a time when insects are not available.

Wildlife managers are concerned about WNS because bats congregate by the thousands in caves and mines to hibernate during winter months. Bats, and possibly even people, are spreading WNS from one cave to the next. The U.S. Fish and Wildlife Service recommends suspending activities in caves to protect bats from white-nose syndrome. The Massachusetts Division of Fisheries and Wildlife owns caves and mines which may not be entered without a permit.

Little Brown BatBats 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 to biologists because bats have a low reproductive rate. Since most bats raise only one pup per year, it would take decades for a bat population to rebound after a large die-off.

Of the eight species of bats currently found in Massachusetts, it appears that the types of bats most affected by WNS are the widespread and common Little Brown Bat, Eastern Pipistrelle and Northern Long-eared Bat. The rare, state listed Small-footed Bat is also affected by WNS. These bats hibernate in caves or mines. Big Brown Bats which generally hibernate in buildings are not yet seriously affected.

The Division of Fisheries and Wildlife (MassWildlife) is asking anyone with a summer colony of ten bats or more on their property to report that information to agency biologists. Little Brown Bats and Big Brown Bats are the most likely species to be found in buildings. Please report the colony's location, what kind of place it is in, and about how many bats are in the colony, by calling (508) 389-6300 or email mass.wildlife@state.ma.us. Everyone's response to this call will be greatly appreciated.

Biologists from state and federal agencies and other conservation organizations across the country are trying to find a way to protect bats from this deadly fungus. Efforts are underway to understand how this fungus is spreading and killing bats. The WNS fungus has just recently been described as a new species of cold-living fungus, but why it has suddenly become a problem is unknown. One theory is that it is a non-native species from bat caves in Europe that has just recently arrived in North America. Researchers are trying to learn more about WNS, what's causing it, how it is transmitted and how to prevent it. Despite the continuing search to find the source of this condition by numerous laboratories and state and federal biologists, the exact cause of the bat deaths remains unknown.

 

Updated: 09/14/2012