It's a condition as mysterious as it is deadly: white-nose syndrome (WNS), a bizarre fungal infection that has killed half a million bats in the U.S. Northeast since it was first observed two years ago.
Despite the name, WNS isn't actually the cause of the deaths—it's a symptom. The cold-loving fungus that causes it, now believed to be a member of the genus Geomyces, grows on bats' facial skin and flight membranes, possibly causing them to starve. No one knows where the fungus came from, or if it is what is directly killing the bats. But in caves where it has been observed, bats have suffered morality rates ranging from 75 to 100 percent.
Evidence of WNS has now been found in New York, Vermont, Massachusetts, Connecticut, New Hampshire, New Jersey, Pennsylvania, and West Virginia. It has affected several species of bats, including the Indiana bat (Myotis sodalis), an endangered species whose population has already dropped by 50 percent in the past 30 years.
With no cure in sight, and further deaths likely, a possible stopgap has now been proposed. Biologists Justin Boyles of Indiana State University, Terre Haute, and Craig Willis of the University of Winnipeg constructed computer models that suggest adding extra heat to bat caves during the winter may give the animals the energy they need to fight off, or at least survive, the fungal infections. Their research was published this week in the journal Frontiers in Ecology and the Environment.
"This is actually an idea we came up with several years before WNS was discovered," Boyles says. "The original idea was that it could help increase survival in hibernating bats that were already endangered, such as the Indiana bat." At the time, the idea was considered unconventional, and "we put it on the back burner," he adds. "But given the scale of the WNS problem and our modeling results, it seems like an unconventional idea that is at least worth thinking about and testing."
In their computer models, Boyles and Willis examined how the disruption of normal hibernation patterns and physiology could have created the mortality rates associated with WNS. They then modeled adding artificial warming zones within hibernation caves, which would lessen the energy costs of the bats' periodic awakenings. In the model, the bats that were provided with additional heat were able to retain enough energy to fight the fungal infection, and survival rates increased by up to 75 percent.
The researchers based their models on the little brown bat (Myotis lucifugus), which has been well-studied. They say that aspects of their model would be applicable to other species in varying degrees. "For example," Boyle says, "the Indiana bat is very similar to the little brown bat morphologically, behaviorally, and ecologically, so the model should be highly applicable to that species as well."
Given the success of their computer models, the authors are now developing a system, using wooden boxes and heating coils, to create toasty pockets in bat caves. They plan to start testing it in the next few weeks, thanks to about $28,000 in funding from the U.S. Fish and Wildlife Service. "We'll be testing it initially in a little brown bat hibernation site in Manitoba, Canada," Boyles says, "well outside the affected area, to eliminate the chance we might increase the rate that the disease spreads."
Since the fungus only grows at temperatures below 68 degrees Fahrenheit (20 degrees Celsius), "We still don't know if the disease can be spread during the summer when the bats are warm," Boyles says. "There's a chance that increasing over winter survival of infected bats might have little effect on the rate that the disease spreads, but we'd want to be very sure of that before testing on WNS affected caves."
Even if their plan works, Boyles is quick to point out that this isn't a cure for WNS. “I can’t even guess what the cure or the solution to this is going to be,” he said in a statement. “We’re going for a stopgap.”
Image of little brown bats (Myotis lucifugus) affected by white-nose syndrome at a graphite mine by Al Hicks, New York Department of Conservation. Used with permission.