Bad news for everyone s favorite flying mammals: The U.S. Fish and Wildlife Service has confirmed that bats at Fern Cave National Wildlife Refuge in Alabama have white nose syndrome. The disease is a fungus that grows on hibernating bats, causing them to exhibit often fatal behavior such as flying outside in cold weather. In eastern North America alone. 5.7 million to 6.7 million bats have died of white nose syndrome. Fern Cave is the winter home for multiple bat species, including the largest documented colony of gray bats, which are federally endangered. So far, the U.S. Fish and Wildlife Service had detected the syndrome in two groups of tri colored bats in the cave.