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Indiana Department of Natural Resources

Fish & Wildlife > White-nose Syndrome in Bats White-nose Syndrome in Bats

two bats showing visible signs of White Nose Syndrome


White-nose syndrome (WNS) is an infectious disease associated with a recently identified fungus (Pseudogymnoascus destructans) responsible for unprecedented levels of mortality among hibernating bats in North America. WNS is named for the white fungal growth that invades the skin tissue on the muzzle, wings and ears of cave-dwelling bats during winter hibernation. The disease was first noted in New York in 2006 and has since spread unchecked to 26 states and five Canadian provinces. The fungus that causes WNS has been found in three additional states. Twelve different bat species, including three federally endangered and one threatened, have been affected by WNS or exposed to the fungus. The disease has caused the death of an estimated 5.7–6.7 million bats across eastern North America with estimates of mortality often exceeding 90 percent in caves that have experienced multiple years of infection.

Scientists and biologists throughout North America are working diligently to understand the fungus, how it affects bats, and how it might be controlled. While the prolific white fungal growth on the bat’s muzzle may be the most striking sign of infection, it’s their wings that may be the most injurious target. During hibernation, the large surface area of a bat’s wings performs critical physiological services such as regulating the animal’s body temperature, water balance, and gas exchange with its external environment. These life processes, which are vital to survival, are disrupted when healthy wing tissue is digested by the invading fungus. Consequently, the hibernation of WNS-infected bats often includes a number of harmful behaviors that appear to be triggered by their inability to regulate essential metabolic activities.

More information about WNS and its impact on bats can be found at

Progression of WNS in Indiana

  • WNS was first detected in Indiana in January 2011 during routine winter hibernacula surveys conducted by Division of Fish & Wildlife bat biologists.
  • By the end of that first winter, the disease had been found in six caves in Crawford, Monroe and Washington counties.
  • During the following winter, bats exhibiting sign of WNS infection were observed in or reported from 20 additional caves that included six new counties (Greene, Harrison, Jefferson, Lawrence, Martin and Orange).
  • Disease surveillance during the 2012-13 winter resulted in WNS detection from nine more caves that included one new county (Jennings).
  • Two caves and one new county (Vermillion) were added from WNS surveillance during the 2013-14 winter.
  • One cave in Jefferson County was added during the 2014-15 winter.
  • WNS is widely distributed throughout much of the karst region in south-central Indiana and locally established within most of the state’s major concentrations of important bat hibernacula.

Impacts of WNS on Wintering Bats in Indiana

For nearly 30 years, Wildlife Diversity biologists in Indiana have conducted population counts of hibernating bats every other winter. This biennial schedule minimizes disturbance but still provides important information needed to monitor the status and health of the state’s bat populations. At present, there are 22 WNS-affected hibernacula in Indiana that have long-term winter bat population counts. The impact of WNS can be assessed by comparing the last count before the disease was detected in a particular site (2009 or 2011) to its most recent count (2014 or 2015). In these sites, the total population of all species combined has dropped from about 176,000 bats in the latest pre-WNS winter to about 123,000 in the most recent post-WNS winter, a decline of about 30 percent. The impact of the disease, however, appears to differ by species. Using the same approach, biologists have tallied the following numbers for Indiana’s most common winter bat species:

  • little brown bats: 90 percent decline (from 7,603 in latest pre-WNS winter to 794 in most recent post-WNS winter)
  • tri-colored bats: 71 percent decline (from 1,323 in latest pre-WNS winter to 384 in most recent post-WNS winter)
  • big brown bats: 51 percent decline (from 208 in latest pre-WNS winter to 102 in most recent post-WNS winter)
  • Indiana bats: 27 percent decline (from 166,891 in latest pre-WNS winter to 121,582 in most recent post-WNS winter)

Status of WNS

For more information on WNS and the federally endangered Indiana bat, click on the following links:

Public Access to IDNR-owned Caves

In response to a growing concern for bat populations affected by WNS in Indiana, the Indiana Department of Natural Resources (IDNR) closed public access to caves, sinkholes, tunnels and abandoned mines on IDNR-owned land in 2009. This action, made in consultation with the U.S. Fish and Wildlife Service, was a preemptive step in an attempt to slow the spread of the deadly fungus that causes WNS. The fungus can be transported from cave to cave on the boots and clothing of people, as well as by bats.

In 2014, the IDNR initiated a pilot program to allow limited access to select caves at Spring Mill State Park and Cave River Valley Natural Area. The program, in partnership with the Indiana Karst Conservancy (IKC), allows for recreational caving during the summer beginning in May 2014. Groups wishing to gain access to select caves in Spring Mill State Park or Cave River Valley Natural Area must apply for a permit and comply with proper WNS decontamination protocols. Groups must register in advance through the IKC and complete an online training module that explains decontamination procedures to prevent the spread of WNS to other caves and states. To learn more about the interim cave access program click here.