May 1, 2014. White-nose syndrome (WNS), a fungal disease that has killed millions of bats in the eastern United States, continues its deadly toll on North Carolina bat populations.
The cold-weather disease, which can kill up to 100 percent of bats in a colony, was first detected in North Carolina in February 2011, in a bat from Avery County. Since that time, biologists with the N.C. Wildlife Resources Commission and the U.S. Fish and Wildlife Service have confirmed the disease in five bat species in eight counties in western North Carolina, with an additional two counties considered suspect for WNS.
During winter cave surveys conducted in January and February 2014, biologists found that some previously WNS-infected locations showed up to a 99 percent decline in hibernating bats over the last two to three years.
At a mine in Avery County, the number of hibernating bats was down from approximately 1,000 in 2011 to 65 bats last year to just 17 this winter. In a Haywood County mine, the number of bats plummeted from nearly 4,000 bats to about 55 bats in only two years.
Even worse than the drop in numbers is the confirmation that WNS is spreading. For the first time, biologists this winter documented WNS-infected bats in Jackson County and saw telltale signs of WNS on bats in Cherokee County, bringing the total number of counties either confirmed or suspect for WNS to 10.
“We continued to find small numbers of dead bats during this last survey, and we also continue to hear reports of unusual bat behavior, such as bats flying during the day in cold weather and flying erratically, which can be signs of a bat infected with white-nose syndrome,” said Gabrielle Graeter, a wildlife diversity biologist with the Commission.
Among bats that hibernate in North Carolina, five species are known to be affected by white-nose syndrome — the tri-colored, Northern long-eared, big brown, Eastern small-footed, and little brown bat. Species with the steepest declines are the little brown bat, the tri-colored bat, and the northern long-eared bat, which have shown declines ranging from 92 to 100 percent in sites that have been infected with WNS for two or three years.
Neither the disease nor the fungus that causes it has been detected in any of the so-called tree roosting bats, which typically roost individually in or on trees in the warmer months and either migrate south for the winter, or remain in the area, hibernating individually outside of caves. The disease has not been detected on the two species of big-eared bats that occur in North Carolina, including the federally endangered Virginia big-eared bat.
White-nose syndrome is named for the whitish, fuzzy fungus that grows on the noses, wings and ears of bats during winter hibernation. Bats infected with WNS awaken more often during hibernation, which causes them to use up essential fat reserves needed to get them through the winter.
While WNS is a cold-weather disease, infected bats may spread fungal spores to other bats and roosts throughout the year. However, the fungus only grows in a narrow range of temperatures (41 to 56 degrees) in high humidity conditions. Although these conditions are prevalent in caves and mines used for hibernation, bat houses are used during the summer months and have no more potential to spread fungal spores than do natural roosts, such as a hollow tree. More information about WNS can be found atwww.whitenosesyndrome.org.
Biologists believe WNS is transmitted from bat to bat but it may be transmitted by humans who inadvertently carry fungal spores from cave to cave on their shoes, clothing and caving gear. As a result, the Commission urges people to help bats by staying out of caves and mines. Linville Caverns, the only commercial cave in western North Carolina, is helping to reduce the spread of WNS by asking visitors to disinfect footwear after visiting the cave by briefly stepping onto a special decontamination mat outside the cave.
While WNS has a deadly effect on bats, it does not affect people — at least not directly. Indirectly, however, it can have a huge impact on humans, according to Graeter.
“Bats are extremely important to ecosystems in the state,” Graeter said. “They have an enormous impact on controlling insect populations. A nursing female bat may consume almost her entire body weight in insects in one night, including insects that harm crops and forests.”
The U.S. Geological Service estimates that loss of bats in North America could lead to agricultural losses exceeding $3.7 billion annually.
Biologists will continue their long-term monitoring efforts of bats in western North Carolina. This summer, they use mist-nets to capture and count bats in summer roosts, and record bat calls through the N.C. Bat Acoustic Monitoring Program, a citizen-scientist effort to assess the effects of WNS and other threats to bat populations in the mountains over time.
“The Wildlife Commission continues working to understand more about how WNS affects bats, how the disease is spreading, trying to better understand species differences in survival and what we can do to help bats survive this deadly infection,” Graeter said.
Funding for the Commission’s bat and white-nose syndrome research and management comes from U.S. Fish and Wildlife Service grants and the Nongame and Endangered Wildlife Fund, which supports wildlife research, conservation and management for animals that are not hunted and fished.
North Carolinians can support this effort as well as other nongame wildlife monitoring, research and management projects in North Carolina by:
- Volunteering for the N.C. Bat Acoustic Monitoring Program or other bat-monitoring projects;
- Creating bat habitat by installing a backyard bat house;
- Donating through the Tax Check-off for Nongame and Endangered Wildlife Fund, listed on the N.C. state income tax form;
- Registering a vehicle or trailer with a N.C. Wildlife Conservation license plate; and,
- Donating online at www.ncwildlife.org/give.