North Carolina Wildlife Resources Commission

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Winter Bat Surveys Document Spread of Deadly Fungus

  • 26 May 2017
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Winter Bat Surveys Document Spread of Deadly Fungus
White nose-syndrome apparent on tri-colored bat. Photo by Corrine Diggins

ASHEVILLE, N.C. (May 26, 2017) — White-nose syndrome, a fungal disease that has killed millions of bats in the eastern United States since it was first detected in 2006, continues its deadly spread in North Carolina.

During winter bat surveys in January and February, biologists with the N.C. Wildlife Resources Commission and N.C. State Parks, documented the first case of WNS in Stokes County, which marks the farthest east record of WNS in North Carolina and the first record of visible WNS in the Piedmont.

Historically, biologists had conducted most bat surveys in the western part of the state because that is where the most bat hibernacula (caves and mines) are found. However, this winter, biologists expanded the survey range to include hibernacula across the state.

In the Stokes County hibernaculum, they found four tricolored bats with visible signs of WNS — a whitish, fuzzy fungus growing on their noses, wings and ears. The only other documentation of WNS outside of the mountains in North Carolina was a site in Stanly County that tested positive for the WNS fungus in 2015. However, during subsequent surveys in 2016 and 2017, biologists found no bats exhibiting the tell-tale signs of WNS. Just to be certain the Stanly County site was WNS free, they took swabs from bats this year and submitted them for testing. Results, which came back this week, indicate WNS was present only in the bats from Stokes County.

While the results provided a bit of good news in an otherwise bleak situation, biologists continued to see low numbers of bats in all the caves and mines they surveyed in western North Carolina, indicating that the large declines in bat populations have already occurred, according to mammalogist Katherine Caldwell.

“What we’re seeing now at these sites is WNS’ devastating aftermath,” Caldwell said. “Most sites we surveyed in western North Carolina had over 90 percent declines in bat populations from their pre-WNS counts, with some declines as high as 99 percent.”

While the steep declines of bat populations in western North Carolina are dismaying, the surveys did reveal a bit of good news: bats in the Piedmont and Coastal Plain were faring better than their western counterparts.

“While we don’t have as much data on sites in the Piedmont and Coastal Plain, we did document the highest number of bats at two of the sites that we have been monitoring for the past four years,” Caldwell said. “Even better, we found a cave in Onslow County that had eight hibernating tri-colored bats, all of which appeared to be WNS free. Caves are relatively unknown in the Coastal Plain so it was real treat to be able to survey this cave.”

White-Nose Syndrome in North Carolina

Biologists first detected WNS in North Carolina in February 2011, in a bat from Avery County. Since that time, the disease has been found in 10 counties in western North Carolina, though WNS is likely present throughout the mountains based on bat decline data. White-nose syndrome has been found in eight bat species, but the largest population declines have occurred in four species — northern long-eared, little brown, tricolored, and Indiana bat. The other four species affected by WNS are big brown, gray, eastern small-footed, and southeastern bat. Why some bat species are hit harder by WNS than others is still a mystery to biologists, but several hypotheses are currently being tested.

 “We know that this fungus only grows in a narrow temperature range, between 41-56 degrees Fahrenheit, in high-humidity conditions like those of a cave/mine so only cave hibernators are at risk,” Caldwell said. “But some species that hibernate in caves are not affected even though they hibernate in caves where other species have the disease.

“As the disease continues to spread west across the continent, other species could be affected. We really just don’t know at this point.”

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 in the two species of big-eared bats that occur in North Carolina, including the federally endangered Virginia big-eared bat.

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 by reducing the number of bats in North American ecosystems.

“Bats in these ecosystems are insectivorous and may consume their body weight in insects in a single night,” Caldwell said. “Many insects eaten by bats are crop and forest pests.”

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 North Carolina, concentrating their efforts on caves and mines in the Piedmont and Coastal Plain. But first they need to find hibernacula to survey— a task that is easier said than done, according to Caldwell.

“If landowners have a cave or mine on their property that they’d allow us to survey, that’d be great,” Caldwell said. “They can contact me at katherine.caldwell@ncwildlife.org for more information.”

How You Can Help

While WNS is transmitted primarily from bat to bat, it can be spread to new sites by humans who inadvertently carry fungal spores from cave to cave on their shoes, clothing and caving gear. The Commission encourages 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.

Other ways North Carolinians can help bat populations in the Tar Heel state are by:

Media Contact:

Jodie B. Owen
919-707-0187
jodie.owen@ncwildlife.org

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