White-nose syndrome decimates North Carolina’s bats
Biologists with the N.C. Wildlife Resources Commission and U.S. Fish and Wildlife Service (Service) have determined that white-nose syndrome (WNS) continues to decimate bat populations in western North Carolina, with some infected locations showing up to a 95 percent decline in hibernating bats over the past one to two years. The disease, which has been confirmed in seven counties in western North Carolina, does not affect people.
Wildlife Commission biologists surveying bat populations have documented declining bat populations by site. The number of bats hibernating in a retired mine in Avery County has plummeted from more than 1,000 bats prior to WNS to around 65 bats in just two years since the disease was discovered. At a mine in Haywood County, the number of bats hibernating dropped from nearly 4,000 bats to about 250 bats in only one year. And at a cave in McDowell County, numbers dropped from almost 300 to only a few bats remaining this winter.
White-nose syndrome continues to spread, affecting bats throughout the mountains. Bats in two additional counties — Rutherford and Buncombe — are now confirmed to have the disease and the disease is suspected in Swain County. First detected in North Carolina in 2011, WNS was confirmed in an abandoned mine in Avery County, a cave at Grandfather Mountain State Park in Avery County, an abandoned mine in Yancey County, Linville Caverns in McDowell County, and from a dead bat found in Transylvania County. In 2012, hibernating bats in Haywood County were confirmed positive for WNS.
In Buncombe County, a dead bat found on the deck of a house was confirmed positive for the disease, while a Rutherford County dead bat in a cave on The Nature Conservancy’s Bat Cave Preserve property also tested positive. In Swain County, two hibernation sites surveyed this year had bats with visible signs of WNS. Laboratory tests later confirmed the presence of the fungus. The fungus can be present on a bat, making that bat “suspect” for WNS, but the bat is not considered to have the disease unless invasion of the skin tissue by the fungus is observed with a microscope.
Across the continent, nine bat species in North America are known to be affected by white-nose syndrome. North Carolina is home to 17 species of bats. While eight of those species have been discovered with the fungus elsewhere, the disease or the fungal spores have been documented on only four species in North Carolina. Those species are the tri-colored, Northern long-eared, big brown, and little brown bats.
Neither the fungus nor the disease 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.
In March 2010, the Wildlife Commission took necessary steps to get ahead of the disease by adopting the “White-nose Syndrome Surveillance and Response Plan for North Carolina” in concert with the Service and many other partners. The plan outlines a number of steps to protect bats while allowing biologists to pinpoint and investigate a possible outbreak as quickly as possible. There is evidence that people may inadvertently spread the disease-causing fungus from cave to cave. Therefore, the most important precaution people can take to help bats is staying out of caves and mines.
The fungus grows on bats in caves during torpor, the hibernation-like state bats enter during winter. Infected bats may spread the fungal spores to other bats and roosts during the warmer summer months. 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 hibernation caves, bat houses are used during the summer months and have no more potential to spread fungal spores than do natural roosts, such as hollow trees.
Bats are important to ecosystems worldwide, including in North Carolina. 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.
Funding for the Commission’s bat and white-nose syndrome research and management comes from Service grants and the Nongame and Endangered Wildlife Fund, which supports wildlife research, conservation and management for animals that are not hunted and fished.
- Carolyn Rickard, North Carolina Wildlife Resources Commission, (919) 707-0124, firstname.lastname@example.org
- Susan Cameron, U.S. Fish and Wildlife Service, (828) 258-3939, ext. 224, email@example.com
- Asheville Ecological Services Field Office
- Big Brown Bat
- Little Brown Bat
- North Carolina
- Northern Long-Eared
- Tri-Colored Bat
- Virginia Big-Eared Bat
- White-Nose Syndrome
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