To the Bat Bunker!

Cold War–era military shelter promises fungus-free hibernation

How do you protect bats from the fungus that has already killed millions of animals and threatens several species with extinction? A Cold War–era military bunker that once held a 40,000-pound nuclear warhead might provide some answers.

The 80-foot-long bunker—part of the decommissioned Loring Air Force Base—is located in Aroostook National Wildlife Refuge in Maine, just two miles south of the Canadian border. Because of its construction and remote location, the bunker’s temperature and humidity are just about perfect for hibernating bats, says Steve Agius, assistant manager at the refuge. “The humidity hovers around 95 percent, and even if it gets to 35 degrees [Fahrenheit] below zero outside, the inside of the bunker stays at about 37 degrees.” But the bunker has one major advantage over natural caves: it can be decontaminated after the bats finish hibernating.

Wildlife officials have been searching for sites of just this kind to serve as hibernacula for bats threatened by Pseudogymnoascus destructans, the fungus that causes white-nose syndrome (WNS). Some scientists have tried creating artificial caves; The Nature Conservancy spent $300,000 to build one in Tennessee. But the Maine bunker already existed and was converted at very little cost.

Biologists first monitored conditions inside the bunker during the winter of 2011. This past winter, they stocked the bunker with 30 little brown bats carried to Maine from Vermont and New York—all of which carried traces of the fungus but did not yet show signs of illness. A motion-activated video recorder monitored the bats’ activity after that; Agius snowmobiled three miles out to the bunker twice a week to check on them. They behaved just as they would have in a cave, he reports. “Every once in a while a bat might wake up, swoop down, take a sip out of one of the drinking pools, and go right back to sleep.” Nine of the bats survived the season, better odds than they would have faced in their native, contaminated caves, where WNS can have a fatality rate of 90 percent or higher.

Biologists spent the summer and fall verifying steam-cleaning techniques to sterilize the bunker. As winter approaches, they plan to use audio recordings of swarming bats to attract new animals to the fungus-free bunker. Similar techniques have been successfully used at the artificial cave in Tennessee. Bats that populate the cave naturally won’t experience the stress of being handled and moved, so Agius expects more bats to survive.

With an area of 2,000 square feet, the bunker could house thousands of animals for the winter. And despite its age, the bunker isn’t going anywhere: as a historic landmark, it can’t be torn down. “It will remain, for perpetuity, as long as the concrete holds up,” says Agius. With luck, the bats will remain as well.

—John R. Platt

Photo ©USFWS/Steve Agius

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