Spying on Bats
By Lori Pruitt
Bloomington Ecological Services Field Office
Wyandotte Cave in Indiana’s O’Bannon Woods State Park is the site of a collaborative study led by the Indiana Department of Natural Resources to examine hibernation behavior of bats that roost in sites infected with White-nose Syndrome. The project, funded primarily by the Service’s White-nose Syndrome Grants to States, uses multiple technologies to assess behavior of hibernating bats.
Technologies deployed at the site include near-infrared and thermal cameras to obtain video imagery of hibernating bats, a beam-break gate that detects and records the dates and times that bats enter and leave the site, and an acoustic bat detection system. We are hopeful that data gathered through these multiple passive surveillance systems and analyzed comprehensively will allow for insights into WNS that no single system would provide.
White-nose Syndrome is caused by a newly-described fungus (Geomyces destructans) that invades the skin tissue of the nose, ears and wings of cave-dwelling bats during hibernation. While the prolific white fungal growth that forms on the nose may be the most striking sign of infection, scientists believe bat wings may be the most important 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, vital to survival, are disrupted when healthy wing membranes are digested by the invading fungus.
WNS-infected bats can exhibit a number of harmful behaviors including, increased activity during hibernation that may include leaving the hibernaculum, even during daylight hours. These behaviors appear to be triggered by their inability to regulate metabolic activities and maintain homeostasis (steady internal conditions). Recording these behaviors is the target of the surveillance systems deployed at Wyandotte.
Wyandotte Cave, which was found to be infected with WNS in January 2011, houses the country's largest known winter population of the endangered Indiana bat (60,000 in 2011). The 2012-13 winter marks the second consecutive year of multiple surveillance methodologies at this historic cave.
In February 2013, a team of biologists entered the site to conduct a survey of hibernating bats. This visit will enable us to estimate the current size of the population in the cave, once all the surveillance data are analyzed. Our active WNS surveillance will help us identify abnormal behaviors in hibernating bats, such as bats arousing too often or movements in and out of the cave entrance. Results of this survey will also help to assess how well our passive surveillance systems reflect the status and impact of WNS at this site.
Collectively, the research and surveillance activities at Wyandotte Cave will help scientists define the processes through which dermal infection by Geomyces destructans results in the onset of disease and, ultimately, causes mortality. Understanding these mechanisms is critical to efforts to manage WNS-affected sites.