News Release

Retired military bunkers used as artificial bat hibernacula at Aroostook National Wildlife Refuge in Maine

April 9, 2013

Steve Agius, 207-328-4634, Ann Froschauer, 703-358-2636,

Little brown bat populations in New England have been decimated by White-Nose Syndrome (WNS), a disease that is responsible for 75 to 90 percent declines in the species population since 2007. WNS is caused by Geomyces destructans (Gd), a fungus of unknown origin in the U.S. that infects bats while they hibernate. As their population continues to decline, the long-term survival of little brown bats in the Northeast is of particular concern.

Wildlife biologists in some states where hibernating bat populations are reaching critically low levels are working toward strategies to monitor and conserve surviving bats, and reduce mortality rates on WNS-affected bat populations.

In an effort to address mortality rates of little brown bats, biologists from the U.S. Fish and Wildlife Service, Maine Department of Inland Fisheries, Vermont Fish and Wildlife, New York Department of Environmental Conservation and Bucknell University have investigated the potential for using decommissioned military bunkers on national wildlife refuges as artificial hibernacula for imperiled bats. These sites could offer predator-free winter habitats for bats where biologists can monitor behavior and implement possible treatments against WNS. These sites may also be decontaminated during summer when bats are absent, which may slow or delay progression of the disease in individuals housed there the next winter.

Aroostook National Wildlife Refuge in Limestone, Maine, has taken the lead in the Northeast on developing and evaluating artificial bat hibernacula as a component of a conservation and recovery strategy for WNS-affected bats. In 2011, the refuge began monitoring and managing temperature and humidity conditions in multiple bunkers to mimic conditions found in caves and mines in the northeast to determine the feasibility of creating artificial cave habitats in which bats could hibernate successfully.

One bunker at Aroostook National Wildlife Refuge was temporarily modified by adding various roosting substrates and shallow pools of water to provide drinking water and increase humidity. In December 2012, 30 hibernating male little brown bats collected from two hibernacula in New York and Vermont and were placed in the Aroostook bunker for hibernation. Motion-sensitive, infrared cameras were used to monitor bat activity and behavior for three months . Throughout the winter, bats were observed hibernating in clusters on the bunker wall, and occasionally flying and drinking water from pools. In late March 2013, biologists entered the bunker to collect all bats, evaluate their conditions, and transport them back to their original caves for release. Although there was mortality among the bats (30 percent survived transport and hibernation), this project has demonstrated that abandoned military bunkers can be managed to create suitable habitat for hibernating little brown bats and may provide a useful strategy to conserve bats affected by WNS. Information collected from this project will help managers enhance bunkers and other potential hibernation sites to provide remnant populations safe hibernation habitat.

Visit our white-nose syndrome blog for more information about the bunker project at Aroostook National Wildlife Refuge:

For photos of the project, visit

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