Researchers find the little brown bat may be evolving to become more resistant to deadly white-nose syndrome

A healthy little brown bat (U.S. Fish and Wildlife Service photo)

University of Michigan biologists have discovered the first genetic evidence of resistance in bats to white-nose syndrome, a fungal disease that has killed millions of the flying mammals in North America, according to a newly published study.

"The study involved northern Michigan populations of the little brown bat, one of the most common bats in eastern North America prior to the arrival of white-nose syndrome in 2006. Since then, some populations of the small, insect-eating bat have experienced declines of more than 90 percent," Jim Erickson reports for University of Michigan News. "UM researchers collected tissue samples from wild little brown bats that survived the disease, as well as individuals killed by the fungal pathogen. They compared the genetic makeup of the two groups and found differences in genes associated with regulating arousal from hibernation, the breakdown of fats and echo-location."

Translation: Bats that are genetically prone to be a little fatter or sleep more deeply may be less susceptible to the disease. The disease kills bats two ways: When the fungus grows on them while they're hibernating, it causes them to use twice as much energy as normal to maintain bodily functions, and sometimes they waste away before making it to spring. The fungus also kills bats when it irritates them so much that they wake up during hibernation and, disoriented, leave the cave in the middle of the winter and starve.

The rapid genetic changes in those areas suggest the bats are evolving due to natural selection. As bats with these genes reproduce, more bats could survive the disease, say the authors.

"While the study was small—involving tissue samples from 25 little brown bats killed by white-nose syndrome and nine bats that survived the disease—the authors say their sample size is large enough to detect genetic changes driven by natural selection," Erickson reports. "A larger follow-up study is underway, expanding both the number of bats and the areas affected by the disease, to develop a fuller picture of adaptive change that may be key to the species’ survival."

Bats play an important role in ecosystems and contribute at least $3 billion annually to the U.S. agriculture economy by pollinating crops, dispersing seeds and keeping insect populations down. But white-nose has decimated bat populations in at least 33 states and experts say some bat species may go extinct because of it.