Night in and night out, bats go about their business with little fanfare, providing important benefits to our environment by eating thousands of mosquitoes, crop-damaging insects and even helping to pollinate plants in certain regions of the country.
Depending on one's perspective, they can be seen as cute or creepy, but few ever thought that one day some once-common species of bats might suddenly be threatened with extinction. For the past five years, a deadly disease called white-nose syndrome has been spreading through Pennsylvania's hibernating bat colonies, wreaking havoc on populations.
First detected in a cave in New York in 2006, the disease is now found in 22 states and five Canadian provinces and has killed an estimated 6.5 million bats in seven years. In Pennsylvania, the Pennsylvania Game Commission monitors 200 important bat hibernation sites out of approximately 6,000 occupied caves and mines statewide.
According to PGC endangered mammal specialist Greg Turner, most of the bat populations at these sites were increasing before WNS arrived. One of the most dramatic examples of how the disease has wiped them out is a well-known and studied mine at Canoe Creek State Park in Blair County, once home to tens of thousands of little brown bats.
"It was gated in 1983 and had about 3,000 bats in there, but over the course of 20 years the population grew exponentially to almost 35,000 bats," Turner said. "Then white-nose syndrome came and those 35,000 bats went down to 155 in two years, and the population was 236 last year, so it's still declining.
"For little brown bats, we're looking at a 99.5 percent population reduction in our monitored sites. That was our most common species prior to white-nose syndrome by far, and to see that many of them go that quickly has certainly raised some concerns."
The U.S. Fish & Wildlife Service said that white-nose syndrome is spread from bat to bat and is also believed it can be transmitted accidentally by humans transporting it from cave to cave on their clothing and gear. Bats affected by the disease develop a white fungus on their muzzles, and it can also be found on their wings and ears.
One theory on how WNS is killing bats is they are aroused frequently from their hibernation, which causes them to burn fat reserves and/or fly out of their hibernacula and freeze to death or fall victim to predators. It is also theorized that they may be suffering from severe dehydration, which can lead to neurological problems.
"We're probably looking in truth at a combination of these two things," Turner said. "If there is hope for bats, it lies in whether survivors of WNS can develop immunity to the disease and pass it on to their young.
"Remaining adults appear to get WNS every year and from what I can tell appear to survive it every year at this point. If the young-born have the same 99 percent mortality rate once they reach the hibernation site for their first year, I seriously doubt these species will be around in 20 to 30 years, but, if they do have a resistant trait that helps them survive, then we'll likely have some stabilization and eventual recovery."
This summer, the PGC is encouraging landowners, environmental groups and Scout troops to take part in the Appalachian Bat Count. Turner says individuals who have a bat colony in their barn or home, or know of a colony somewhere, can go out and count the bats that emerge 1-2 nights a year, which will help provide valuable data for researchers.
To participate, access the PGC website at www.pgc.state.pa.us, click on the link for "Wildlife" in the menu bar at the top of the homepage, click on "Wildlife" in the drop-down menu, then scroll down and click on "White-Nose Syndrome" in the Wildlife Disease section.