News Report bat colonies to protect endangered bats

MassWildlife is working to ensure endangered bats do not disappear forever.
  • Division of Fisheries and Wildlife
  • MassWildlife's Natural Heritage & Endangered Species Program
Little brown bats in an attic.

The past two years, MassWildlife asked you to report bat colonies to help better assess where bats are during the summer months in Massachusetts. Your help is needed again this year. If there is a colony of 10 or more bats on your property, please report colonies here. Colonies may be found in trees, buildings, attics, barns, sheds, or other outbuildings. This information will be used to help conserve the state’s endangered population of little brown bats. 

Since the onset of white-nose syndrome (WNS) in Massachusetts, the state’s population of little brown bats has dwindled to less than 1% of what it once was. In one abandoned mine, almost every bat hibernating over the 2008/2009 winter died from WNS—nearly 10,000 bats dropped to just 14. First seen in bats hibernating in a cave near Albany, New York in 2006, WNS is caused by a fungus that grows on cave-hibernating bats during the winter. The growing fungus rouses the bats from hibernation, causing them to use up precious fat stores before fully waking in the spring, leading to starvation. As a result of the drastic mortality from WNS, all species of cave bats that hibernate in Massachusetts are now listed as endangered on the Massachusetts Endangered Species List.

Two species of bats—the little brown bat and the big brown bat—form summer colonies in trees, buildings, attics, barns, sheds, and other outbuildings in Massachusetts. Little brown bats also hibernate in caves during the winter, where they can contract WNS. Before WNS, little brown bats were the most common bat species in the state. Now, they are one of the species most affected by WNS in Massachusetts. MassWildlife is especially interested in understanding the post-WNS status of little brown bat populations, including knowing the size and location of their colonies.

During the 2018 summer bat maternity season (June–July), MassWildlife partnered with the Biodiversity Research Institute (BRI) to survey bats throughout Massachusetts and to locate little brown bat maternity colonies where mothers group together to raise their young. Bats were located by listening for their calls with special acoustic detectors, mist netting, radio telemetry, and visits to reported roost sites. BRI captured 32 individual bats of three species and tracked two little brown bats to three roost sites. The highest emergence count at a roost site was 125 individuals.

Also in 2018, a second contractor surveyed known historic little brown bats colonies to determine the presence or absence of this species post-WNS. Unfortunately, only a few little brown bat colonies from the historical database still remain. However, this is an ongoing effort and several sites still need to be surveyed.

MassWildlife is committed to reducing the vulnerability of the surviving populations of little brown bats. “This is a great opportunity for the residents of Massachusetts to help in the conservation of an endangered species right in their backyard,” says Jen Longsdorf, who is a part of MassWildlife’s Natural Heritage and Endangered Species Program. Many thanks to those who previously reported bat colonies and roost sites throughout Massachusetts. Since MassWildlife began tracking public reports of bat colonies in 2017, over 200 reports have been received. These reports will result in the location of additional new little brown bat maternity colonies that can be monitored and protected in Massachusetts. 

Learn more about white-nose syndrome in Massachusetts.

Division of Fisheries and Wildlife 

MassWildlife is responsible for the conservation of freshwater fish and wildlife in the Commonwealth, including endangered plants and animals. MassWildlife restores, protects, and manages land for wildlife to thrive and for people to enjoy.

MassWildlife's Natural Heritage & Endangered Species Program 

The Natural Heritage & Endangered Species Program is responsible for the conservation and protection of hundreds of species that are not hunted, fished, trapped, or commercially harvested in the state, as well as the protection of the natural communities that make up their habitats.