Bat Disease Concerns Biologists
By M. Keith Hudson, Wildlife Biologist, Alabama Division of Wildlife and Freshwater Fisheries
A rapidly-spreading affliction among bats, causing 95 percent mortality in some bat species at some sites, is a concern for wildlife experts. Biologists have named it white-nose syndrome (WNS) after the white, cotton-appearing fungal growth that most often appears around an infected bat’s nose, ears or wing membrane. WNS is affecting hibernating, cave-dwelling bats in the eastern United States. The affliction was first documented at four sites in New York state during the winter of 2006-07.
WNS is apparently caused by a newly identified fungus of the Geomyces type that thrives in cold and humid conditions such as that of caves used by some bats during hibernation. Signs of the affliction include the presence of the white fungus on bats, bats flying outside during the day in cold weather, bats clustered near the entrance of their hibernating caves and abnormal numbers of dead bats around cave entrances. Several species of cave-dwelling bats have been affected, including the Tri-colored, little brown, northern long-eared, big brown, small-footed and Indiana bats. WNS is not known to affect humans.
On March 1, 2012, a team of surveyors from Alabama A&M University and the National Park Service, coordinated by the Alabama Bat Working Group, were conducting a bat survey in Russell Cave in Jackson County, Ala. where they saw numerous bats displaying symptomatic white patches of fungus on their skin. Two tri-colored bats and tissue samples from a northern long-eared bat from the cave were sent to the Southeastern Cooperative Wildlife Disease Study unit at the University of Georgia for testing, which confirmed the presence of white-nose syndrome.
So, regrettably, white-nose syndrome is now in some of Alabama’s bats and the Alabama Department of Conservation and Natural Resources is very concerned about how it will impact the state’s bat population. Of particular concern is the potential for WNS to inflict the gray bat, an endangered species, which uses caves year round. The Tennessee Valley region of north Alabama is “gray bat central” and contains several large gray bat colonies. These include the species’ largest summer roosting colony at Sauta Cave National Wildlife Refuge, where as many as half a million spend the summer, and the largest winter hibernating colony at Fern Cave National Wildlife Refuge, where several million gray bats hibernate during the winter. Most biologists feel it is just a matter of time before WNS spreads to gray bats, with the potential to devastate this endangered species. Scientists are also particularly concerned about the Indiana bat, also an endangered species, whose status was precarious even before WNS showed up.
Across the eastern United States, biologists have rapidly mobilized in an attempt to control WNS by taking three approaches: research, monitoring/management and outreach. Wildlife pathologists are continuing to study the fungus and its effect on bats, hoping a cure or treatment can be found. The U.S. Fish and Wildlife Service and U.S. Forest Service have closed all caves on these federal lands in states where WNS has been found. The U.S. Fish and Wildlife Service has also recommended a voluntary cessation of all recreational caving in affected states and states that adjoin them. Many state wildlife agencies in affected states have followed suit and also closed their state-owned/managed caves.
Though WNS is likely spread from bat to bat, there is some evidence that caving activities by humans may also play a role by spreading fungal spores from cave to cave via footwear and caving gear. Voluntary cessation of recreational caving is quite controversial within organizations of recreational cavers, often called cavers or spelunkers. However, caving organizations such as the National Speleological Society have been, for the most part, very helpful, understanding and concerned about the spread of this devastating fungus.
It is possible that nothing can be done to halt the spread of WNS. Until a treatment or cure can be found it will likely be bad news for Alabama’s cave-dwelling, colonial bats. If so, the bats that have a natural immunity to this fungus (as they do for other non-lethal fungi) may survive. The few bats of each species that are naturally resistant to WNS would pass this genetic resistance to future generations. We might see natural selection before our eyes…survival of the fittest – that is, the evolution of bats naturally resistant to the affliction. Hopefully, we will not lose entire species of bats or the benefits they provide in the process.
Bat photo by Dr. William E. Stone courtesy of the US Fish and Wildlife Service.