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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 25 states and five Canadian provinces. The fungus that causes WNS has been found in three additional states. Ten different bat species, including three that are federally endangered and one proposed as endangered, 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% in caves that have experienced multiple years of infection.
Scientists and biologists throughout North America are working diligently to try 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 membranes are invaded by the fungus. Consequently, the hibernation strategy of WNS-infected bats often includes a number of harmful behaviors. An example is exiting caves during cold winter days, which appears to be triggered by their inability to regulate essential metabolic activities.
More detailed information about WNS can be found at whitenosesyndrome.org.
Progression of WNS in Indiana
Impacts of WNS on Wintering Bats in Indiana
DFW biologists in Indiana conduct population counts of hibernating bats every other winter. This biennial schedule minimizes disturbance yet still provides important information needed to monitor the status and health of winter bat populations. Since the initial detection of WNS in Indiana in 2011, biologists have obtained estimates of bat populations from 15 caves that have been infected with WNS for at least three winters. In these sites, the total population of all species combined has dropped from about 127,000 bats in the first winter to about 100,000 by the third winter, a decline of approximately 21%. The impact of the disease, however, appears to differ by species. During the same period, biologists tallied the following numbers for Indiana’s most common winter bat species:
Counts scheduled for the upcoming 2014-15 winter will provide the first opportunity to evaluate the impact of WNS on bat populations in Indiana’s most significant hibernacula, most of which will have been infected for five winters.
Status of WNS
For more information on WNS and the federally endangered Indiana bat, click on the following links:
Public Access to DNR-owned Caves
In response to a growing concern for bat populations in Indiana affected by WNS, the Indiana Department of Natural Resources (DNR) has closed public access to caves, sinkholes, tunnels, and abandoned mines on DNR-owned land until further notice. Exceptions to the closure are select caves at Spring Mill State Park, Cave River Valley Natural Area, and McCormick’s Creek State Park. This action, made in consultation with the U.S. Fish and Wildlife Service in 2009, 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 the bats.
In 2014, the Indiana DNR 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 by groups on an interim basis beginning in May 2014. Groups wishing to gain access 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.