White-Nose Syndrome Killed Over 90% of Three North American Bat Species

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White-nose syndrome has killed over 90% of northern long-eared, little brown and tri-colored bat populations in fewer than 10 years, according to a new study published in Conservation Biology. Researchers also noted declines in Indiana bat and big brown bat populations.

Annual change in winter colony size of little brown bats (2000 – 2019) as WNS spread across the eastern U.S. and Canada. Shrinking red circles indicate bat colony size; expanding gray shading depicts WNS-positive counties by detection year. (Public domain.)

The findings, detailed in “The scope and severity of white-nose syndrome on hibernating bats in North America,” underscore the devastating impacts of the deadly fungal disease. The research tapped into the most comprehensive data set on North American bat populations to date, which includes data from over 200 locations in 27 states and two Canadian provinces.

The findings represent the work of 60 individual collaborators, 37 organizations and hundreds of field technicians and volunteers who participated in winter surveys of bats over a 23-year period. The data was compiled by the North American Bat Monitoring Program (NABat), which was established by the U.S. Geological Survey and U.S. Fish and Wildlife Service (Service), along with many partners, to improve conservation science for bats.

The Service leads the national response to white-nose syndrome through a collaborative effort that includes coordination among state, federal, tribal and non-governmental partners. The agency also offers grants to institutions and natural resource management agencies to advance disease research and identify new solutions. Since 2015, NABat has been building infrastructure and coordinating efforts in response to the need for continental-scale monitoring to inform management of white-nose syndrome, as well as other threats to bats.

“The impacts of white-nose syndrome on bat populations have been swift and severe, but we are not without hope,” said Jeremy Coleman, national white-nose syndrome coordinator for the Service and an author on the paper. “Through strong collaborative efforts like this analysis, we continue to learn more about the dynamics of this disease and we will build the infrastructure we need to conserve native bats for future generations.”

White-nose syndrome is a disease that affects hibernating bats and is caused by an invasive, cold-loving fungus. The fungus grows on bats’ skin, disturbing their hibernation and resulting in dehydration, starvation and often death. First documented in New York in 2006, white-nose syndrome has since spread to 35 states and seven Canadian provinces and has been confirmed in 12 North American bat species.

“The severity of the impact of this disease on bat populations is staggering. We found that nine out of 10 bats of the most vulnerable species are now gone,” said Winifred Frick, chief scientist of Bat Conservation International and an author on the paper. “Bats are essential to our ecosystems, and our results that stem from working with so many biologists across the United States and Canada focus our efforts on how best to protect these important mammals.”

Northern long-eared bat with visible symptoms of WNS

This Northern long-eared bat shows growth of the fungus that causes white-nose syndrome. (Credit: Steve Taylor, University of Illinois)

“With this collaborative study, we clearly illuminate the scale of the loss resulting from white-nose syndrome, which is both quantitatively severe and geographically pervasive,” said Carl Herzog, senior wildlife biologist for the New York State Department of Environmental Conservation and an author on the paper. “The story it tells is grim, to be sure, but having a clear view of what we are up against is an important precursor to mounting an effective management response.”

Limited multi-state, range-wide analyses of once common bat species have made it difficult to understand the role of local populations in overall species viability. Ongoing declines in northern long-eared bats led the Service to protect the species under the Endangered Species Act and to initiate reviews of little brown bats and tricolored bats. Individual states and Canada have also enacted additional protections for bats.

“State fish and wildlife agencies welcomed the opportunity to collaborate on this important evaluation,” said Jenny Dickson, wildlife division director for the Connecticut Department of Energy and Environmental Protection and chair of the Association of Fish & Wildlife Agencies Bat Working Group. “We are pleased to be able to share data collected through projects frequently funded by federal grants to help quantify the extent of this conservation challenge. It helps others understand what we’ve seen firsthand – once common species have declined by over 90% in less than 10 years.”

There is no known cure for white-nose syndrome, but scientists worldwide are working together to study the disease and determine how it can be controlled. Bats eat insects and are critical pest controllers. In the United States alone, bats are estimated to save farmers at least $3.7 billion per year in pest control services. The loss of so many nighttime insect predators can have cascading effects on the environment, with potential to affect forestry, agriculture and human health.

For more information about white-nose syndrome, please visit www.whitenosesyndrome.org.