A Refined Technique On Sampling Bat Population Sizes Developed
Brett Smith for redOrbit.com – Your Universe Online
For years, researchers have been using acoustic monitoring technology to assess the bat population in specific areas. Researchers conducting a new study around Form Drum in upstate New York have now developed a refined method on this non-invasive sampling technique.
Published in the Journal of Ecology and the Natural Environment, the new study concluded that transect sampling — installing a row of detectors for a week, then moving them — gathered data on a larger area with greater disparity of habitat than stations set up for the entire season. However, transect sampling requires more time and effort.
The team noted that their work was partially motivated by the Army’s need to determine Fort Drum’s impact on the local bat population. Many bat populations in the area have been decimated by white-nose syndrome, a deadly fungal infection known for the white growths it causes on the nose of infected bats.
“The Department of Defense is compelled to follow the Endangered Species Act,” said W. Mark Ford, the leader of the Virginia Cooperative Fish and Wildlife Research Unit at Virginia Tech. “Hence they are required to monitor the endangered Indiana bat to assess how military training, range sustainment, and other environmental stewardship efforts, such as forestry and ecological restoration, impact the species.”
“The challenge is that, as a result of white-nose syndrome, you cannot monitor bats by catching them because there are too few,” Ford added. “But they are still there, and the act still applies. So we use acoustics to say ‘present here, go slow; absent here, go ahead.’”
The study researcher noted that the big brown bat, which is only modestly impacted by white-nose syndrome, and bat varieties not affected by the fungal infection were easy to find despite the sampling method used to find them. The endangered Indiana bat and little brown bat needed both long-term sampling and transect sampling over a wide area in order to ascertain that they were even present, even though scientists knew their preferred roosting and foraging areas. Not knowing these areas made detection even more difficult for species like the tri-colored and northern long-eared bats.
“For species like the northern long-eared bat or tri-colored bat for which Fort Drum managers do not have as much historic maternity colony data, we have to ‘think like a bat’ and try to monitor in areas of suitable habitat or expected use on what we know about the species’ natural history,” said Laci S. Coleman, who conducted the research as part of her graduate degree in fisheries and wildlife sciences from Virginia Tech.
The researchers concluded that transect sampling “in areas of known previous use, expected use, or suitable habitat is likely more effective than deploying detectors for long periods or at permanent stations.”
“Transect sampling is a time-consuming commodity that busy natural resource managers tasked with maintaining military installations have in very short supply, considering today’s management demands,” Ford said.
However, he added, “knowing how to determine population numbers relatively rapidly in a science-based way is important in order to move several of these species to endangered status and make land-use decisions accordingly.”