Noninvasive Technique for Identifying Bat Populations Tested by US Government Researchers

Wildlife biologists studying the deadly white-nose syndrome that's ravaging bat colonies across North America have begun recording the bats' echolocation calls in order to identify different bat species in a study region.

Writing in the Journal of Ecology and the Natural Environment, researchers from Virginia Tech, the US Geological Survey and the US Army report that recording bat calls is the most efficient and least intrusive way of identifying bat species in a given area.

Recording bats also provides insights into which populations have been affected by white-nose syndrome, or WNS, the killer bat disease that has led to the deaths of more than 6 million bats in North America since it was first detected in 2006.

"Acoustic sampling is a noninvasive sampling technique for bats, and its use often allows for the detection of a greater number of bat species in less time than traditional sampling methods such as netting," said study co-author W. Mark Ford, a USGS scientist at the Virginia Cooperative Fish and Wildlife Research Unit at Virginia Tech.

"Low population numbers make netting both time and cost prohibitive," Ford said. "Netting also has low capture rates for WNS affected species. Moreover, acoustic sampling minimizes the handling of bats, which lessens the chance of unintended cross-contamination and exposure to the white-nose fungus from one bat to another or from equipment and personnel to uninfected bats."

WNS has taken a toll on the endangered Indiana bat, the little brown bat and the northern long-eared bat, each of which has experienced severe disease-related declines, particularly in the Northeast and central Appalachians.

Working in Fort Drum, N.Y., where the terrain is a mixture of wetlands, mature forests, newly regenerating sites and a large river corridor, gave the researchers an optimal habitat to study both little brown bats and Indiana bats.

Bats were abundant in the Fort Drum region before WNS was reported there in 2008, Ford said.

"These species have not been eliminated, but because of white-nose syndrome they occur in low numbers," Ford said. "Acoustic sampling allows us to sample for affected bat species and determine where on the landscape they are and what habitats they continue to use. At Fort Drum, these data are critical for the Army's land managers and the US Fish and Wildlife Service's regulators in working together to conserve endangered and declining bat species while providing range conditions necessary for the military mission."

Wildlife and forest managers are seeking non-intrusive ways to survey bats in their regions, the researchers said, adding that their acoustic monitoring technique could be adopted by seeking alternative methods to determine the presence of bats.

"This long term data collection effort made the study particularly useful for managers, including the US Fish and Wildlife Service, which, because of white-nose syndromes devastating effects, announced a proposed rule to list the northern long-eared bat as an endangered species in 2013," Ford said.