White Noise Syndrome: An emergent disease battering North American Bat populations

Brilee Coleman

Originally published March 5, 2015

Photo by: Brilee Coleman

If you think bats flying out of haunted houses are scary, imagine finding thousands of bat bodies lying around in the woods one morning. This is exactly what happened when White Nose Syndrome, or WNS, was discovered in 2006, and Myotis lucifugus (little brown bats) were discovered strewn outside of caves in New Albany, New York. WNS is a fatal disease named for a fungal infection found on the noses of hibernating bats. The disease kills bats by causing them to rouse from hibernation prematurely, after which bats wander out into the daylight in the middle of winter, where they die from lack of food and low temperatures. Typically, hibernating bats venture deep into caves where they seek shelter for the winter, called hibernacula. Bats affected by WNS, however, can be found hibernating at the mouths of caves, where temperatures are less stable. These changes in bat behavior have resulted in a loss of 5.7 million to 6.7 million bats of at least 11 different species since the discovery of WNS in 2006. It is believed that WNS was brought to North America from Europe, where the disease is present, but bats are unaffected. Because bats do not travel between continents, it is likely that WNS was transported on the shoes of cavers traveling from Europe to the United States. Since its arrival in North America, WNS has been documented in 25 states and several Canadian provinces.

So how does having a “white nose” result in strange hibernation behavior and death in bats? Hibernating bats have decreased metabolic activity, which allows them to survive the winter by slowly burning off fat stores for energy. Unfortunately for the bats, decreased energy expenditure also leads to suppressed immune function, leaving them vulnerable to infections. Research has shown that WNS is caused by a previously unidentified fungus, Pseudogymnoascus destructans. P. destructans is a psychrophilic (cold-loving) fungus that only functions at temperatures below 20°C, making bat hibernacula perfect environments for fungus growth. Infection of bat tissue with P. destructans leads to more frequent arousals during hibernation, which can result in increased energy expenditure and premature emergence from hibernacula. In the event that bats do survive through the winter, they emerge from hibernation in a weakened state. Because of WNS, even the little brown bat, the most common bat species in the United States, is in danger of extinction.

Why is preventing WNS important?

Bats are critical members of North American ecosystems, and humans benefit greatly from their presence. They are excellent pest control agents, consuming over 1,000 mosquito-sized insects per bat every hour. Many of these bugs are forest or agricultural pests that we would otherwise spend an estimated $3 billion per year paying to control. While bees may get most of the credit for pollination, bats are often-unsung heroes of pollination themselves. If you enjoy having tequila made from agave plants with a side of guacamole made from avocados, thank the bats responsible for pollinating both. Among other plants, bats are also known to pollinate bananas, mangoes, cocoa, and guava. Downstream of initial loss of pest control and pollination of avocado crops, the extinction of North American bat species would likely have major unknown consequences on both economic and ecological health in affected areas.

In addition to having an ecological impact, bats have also served as inspiration for human innovation. Bat Simultaneous Localization and Mapping (BatSLAM) is a radar system modeled on bat echolocation. BatSLAM helps solve the problem of robots navigating and localizing themselves in complex environments, allowing for the development of more autonomous robots.  In addition, biomimetic skins modeled on bat wing properties have allowed for unprecedented flying capabilities in small aerial vehicles, such as controlling various wing shapes and flight modes mid-flight.  Without access to bats for research purposes, these efforts would likely come to a halt.

What is being done about WNS?

There is currently no cure for WNS, although it remains an active area of research. In the absence of a cure, conservation of bat habitats and quarantine of affected caves are critical steps in the effort to prevent the spread of WNS. Current approaches include closing off caves known to be contaminated with WNS and using biosecurity measures to prevent cavers from introducing WNS to caves that are known to be clean. Some things that everyone can do to help prevent the spread of WNS are reporting strange bat behavior, such as flying during the day, to the Georgia Department of Natural Resources, staying out of bat hibernation sites, limiting disturbances to natural bat habitats around your home by reducing outdoor lighting and minimizing tree clearance, and educating others on the many values of bats.  For those interested in actively participating in bat conservation, the Georgia Department of Natural Resources provides information on how to build bat roosting boxes and other volunteer opportunities at their website: http://www.georgiawildlife.com/Conservation/Bats. For more information about WNS, visit: https://www.whitenosesyndrome.org/.