White nose syndrome could have devastating impact on local bat ecosystems
Monday, August 26, 2013 3:50 AM
A news release on Aug. 9 by the Minnesota Department of Natural Resources (DNR) confirmed the results of a study done in five Minnesota caves, which confirmed the presence of spores from fungus Pseudogymnoascus destructans at three of those sites. One of those sites was Mystery Cave at Forestville/Mystery Cave State Park, located near Spring Valley.
The report has raised great concern for the future of bat populations within the state as the fungus is strongly associated with white-nose syndrome (WNS), a disease assumed to be responsible for massive bat-kills in Europe, Canada and eastern United States.
Approximately 5.7 million hibernating bats have already died from the disease since the discovery of WNS in 2006. Faced with severe bat population losses and possible species extinction, local DNR naturalist Warren Netherton said, "It will be a sad day to lose them."
WNS has been the source of much frustration due not only to its quick-spreading destructiveness, but also because of how little is known about the disease.
The U.S. Fish and Wildlife Service has set up a National Plan for Assisting States, Federal Agencies and Tribes in Managing White-Nose Syndrome in Bats and given almost $8 million to investigate WNS and discover ways to manage its spread and destructiveness.
Minnesota is one of 27 states and five Canadian provinces that have the fungus for WNS either confirmed present or highly probable.
The fungus grows well in temperatures found in caves and underground mines. Bats, which hibernate in these sites during the winter, come into contact with the fungus and then spread it to other bats they come into contact with.
The disease is named WNS because infected bats typically have the fungus growing on their noses and wings. Although the science backing up the claims is incomplete, it is thought that the fungus interrupts the bats hibernation, causing them to more quickly burn the fat they have stored for the winter. Many die of starvation. Others die when they fly outside into frigid temperatures. The fungus may play a role in confusing bats.
The costs have been incredible with mortality rates among hibernating bat populations within the 90 to 100 percent range.
Since information regarding WNS is still forthcoming as studies are completed and analyzed, increasing public awareness of the disease has become a major goal for naturalists and cave owners.
Netherton said the initial discovery of the disease caused the "Draconian" closure of caves and state forests throughout the eastern states.
"There is a great frustration in wanting to do something, but not being able to do something about it," he added.
Being able to share the plight of the bats is natural at Mystery Cave, which over 2,000 bats call home during the winter months.
Netherton, who manages the cave, said it isn't unusual to see bats flying around in the cave during the spring and fall, "to the delight of visitors whether they like them or not."
Bats were the occasional discussion topic on tours before the Aug. 9 announcement, but now they are mandatory. Any visitor to the cave today will see the usual informational notices in the visitors' center, but they will also hear a message about WNS during their tour.
"The story about WNS is one that saddens people, especially when people see the bats flying around," said Netherton. Mystery Cave has its own bat culture, with night programs, exhibits and sculptures, all telling the story of the bats that live there.
Of the seven hibernating bat species that live in Minnesota, Mystery Cave sees four of them: little brown, big brown, tricolored, and northern-eared. All are susceptible to the fungus and WNS, albeit at varying degrees.
The little brown and big brown bats are known to die off more quickly than the other species. Female bats usually only have one to two pups per year, which would mean decimated populations would have a difficult time resurging. Extinction is even possible for several species, including the grey bat and Indiana bat.
Since the report of the presence of the fungus in Minnesota, the DNR has been evaluating other ways to prevent its spread. The DNR is currently gathering information from caves which installed "bio mats" to remove spores from visitors' feet as they leave the cave. The technology is a mat that looks like artificial grass and is about 75 percent effective in removing spores.
DNR resource coordinator for parks and trails Ed Quinn said the mats would need to be custom made for the cave and ensure safety and ADA compliance.
A second possible decontamination technology would be a mat saturated with a disinfectant. Quinn said the first technology would most likely be the only one installed at Mystery Cave.
Netherton also recommended visitors not wear the same clothes they wear in Mystery Cave at other caves since spores may travel on other clothing. The fungus is not harmful to humans, at least in the direct sense.
"The impacts are huge to the ecosystem," explained Netherton.
He estimated the 2,000 bats in Forestville State Park consume 30 pounds of insects each night during the summer months.
"If we lose the bats, we'll have half a ton more insects flying around each month. Thirty pounds is a conservative number," he stressed.
Many of those insects cause anything from simple human irritation to serious crop damage. "Bats are the only major predator of night flying insects," stated Netherton.
That increase of crop-damaging insects would drive up pesticide use, which would increase costs to farmers and consumers throughout the United States.
Increased pesticide use would also affect the health of humans and other species.
One glimmer of hope is through natural selection. Those bats that have a genetic mutation allowing them to survive the ravages of WNS would be those from which future bat populations would be started.
DNR information officer for the Nongame Wildlife Division Lori Naumann reported that European bat populations have already started to show signs of growth because of immune bats.
Studies based in Canada have been experimenting with mating susceptible North American bats with immune European bats to see if the immunity trait is passed on to offspring.
However, much of the research has been developing slowly while the fungus and effects of WNS continue to cripple bat populations.
Naumann said the long-term effects of losing a vast majority of bats cannot be known yet. Until the feared inevitable population collapse commences locally, cavers, farmers and naturalists alike will be hoping for a solution to come forth.