Environment DEC
From the January 2010 issue
Bat Populations Down 90 Percent in Caves Affected by White Nose Syndrome
Populations of some bat species have plummeted more than 90 percent in northeast caves impacted by "white nose syndrome" (WNS) according to an extensive investigation by the New York State Department of Environmental Conservation (DEC). Surveying 23 caves at the epicenter of the bat die-off in early 2009, researchers found an alarming decline-91 percent on average-in the number of hibernating bats. The study included 18 caves in eastern New York, four in western Massachusetts and one in Vermont.
Not all species have reacted the same to WNS. Those that prefer warmer, wetter roosting spots have been impacted most severely. For example, the little brown bat has declined by an average of 93 percent (little browns account for 85 percent of all the bats that hibernate in the Northeast).
Populations of the endangered Indiana bat have declined less severely than the Little brown bats.
A separate survey of the endangered Indiana bat showed it declined 53 percent on average. DEC bat specialist Alan Hicks-who gave a standing-room-only presentation at DEC headquarters on this topic-said roost conditions may explain part but not all of the difference. Indiana bats prefer a colder, dryer hibernating area. Also, the survey of Indiana bats found stark contrasts between sites. For example, two former mines in Ulster County showed Indiana bat declines of 97 and 29 percent respectively, with no obvious physical differences other than humidity.
The disease was first discovered in some New York State caves in winter 2006-07. The most obvious symptom is a white fungus encircling the noses of some, but not all, of the bats.This fungus (Geomyces destructans) is a prime suspect as a causative agent although that has not been confirmed. Impacted bats deplete their fat reserves months before they would normally emerge from hibernation and die as a result.
Survey Prompts Recommended Closures
DEC, with the help of officials from the U.S. Fish and Wildlife Service (USFWS), other states, academia and volunteers, began an extensive cave survey in January 2009. This typically involved spending hours trekking deep into caves, snapping thousands of photographs of hibernating bats, then counting the individual bats and preparing a database. These counts were then compared to previous surveys.
Dead bats litter the floor of this cave. Because bats congregate in high numbers in a few areas, WNS spreads quickly through each cave.
Bats are particularly vulnerable to disease during hibernation because they congregate in large numbers in caves in clusters of 300 per square foot in some locations. The majority of hibernacula surveyed are found in eastern New York, especially in Schoharie and Albany counties. The 23 caves surveyed are estimated to have once harbored roughly 55,000 bats, approximately 10 percent of the regional bat population. The U.S. Fish and Wildlife Service recommended closing access to caves that have not been impacted by WNS to reduce its spread while scientists work to better understand a cause and find a way to stop the mysterious disease.
Video Surveillance
In mid-October, DEC biologists helped set up video cameras in a mine where WNS has severely impacted hibernating bats. The U.S. Geological Survey (USGS) and National Park Service planned and funded the project. The video surveillance will monitor for aberrant behaviors of hibernating bats, such as excessive grooming, unusually long periods of activity or winter flight. USGS researchers are assessing whether such behaviors could be the link between skin infection by the fungus and death by starvation after premature depletion of winter fat reserves. Preliminary results are expected by late spring 2010. More information is available on DEC's website.
