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US Fish & Wildlife Service FieldNotes

Did You Hear? U.S. Fish and Wildlife Service Drafts Acoustic Survey Protocols for Indiana Bats

Region 3, September 26, 2012

Over the past year and a half, U.S. Fish and Wildlife Service biologists from Regions 2, 3, 4 and 5 have led a multi-agency team in drafting revisions to the current summer survey guidelines for conducting presence/probable absence surveys for the federally endangered Indiana bat (Myotis sodalis). As currently proposed, acoustic surveys would become the primary technique for determining if Indiana bats are present during the summer in proposed project areas and would be followed by mist net surveys and radio-tracking studies if the species was positively detected. The new protocols were drafted in response to several factors: (1) the existing Indiana bat survey protocols published in 2007 recognized the potential role that acoustic monitoring can play, but only provided protocols for using mist nets; (2) increasing frequency of use of acoustic monitoring at wind-energy projects without standardized protocols; and (3) documented declines in mist-netting capture rates and detection probability in areas with declining Indiana bat populations due to white-nose syndrome.

Acoustic sampling with electronic bat detectors has become a common, powerful technique used by researchers and biologists with government agencies, environmental consulting firms and academics for monitoring the activity of echolocating bats and for collecting behavioral, presence/absence and relative abundance data. The results of research relying on bat detectors inform our understanding of bat ecology and behavior and are increasingly used to guide important wildlife management decisions. Acoustic monitoring is non-intrusive, typically less labor-intensive than mist netting, and capable of recording large quantities of data over extended periods of time. However, the use of this technique is not without some technical difficulties and challenges. For example, accurately differentiating between similarly sounding species may not always be possible, especially when echolocation calls are recorded under less than ideal field conditions.

The Service-led team working on the revised survey guidelines is comprised of state and federal agency experts in one or more of the following subject areas: (1) Indiana bat conservation; (2) federal Endangered Species Act implementation; (3) use of acoustic detection devices and mist-netting; and (4) acoustic-call identification. Individuals outside of federal government who were not state employees serving in their official capacities at the direction of elected state officials were not considered for inclusion in the initial survey protocol team to avoid any conflicts of interest or potential personal/commercial gain and to ensure compliance with the Federal Advisory Committee Act.
The Service conducted a peer review of the first draft of the summer survey guidelines in February 2012 and is currently preparing a second draft that will be available for critical review during a public comment period that will be announced in the Federal Register in the fall of 2012. Implementation of a final version of the revised survey guidelines may occur as early as the summer of 2013.
The first draft of the Indiana bat summer survey guidelines and supporting information is available at the Service’s Indiana bat summer survey guidelines website (http://www.fws.gov/midwest/Endangered/mammals/inba/inbasummersurveyguidance.html).

Contact Info: Larry Dean, 612-713-5312, Larry_Dean@fws.gov