A continental-scale study of acoustic phenology to improve population monitoring and inform management of hibernating bats

Science Center Objects

Bat Research

Research collaboration: Winifred Frick (Bat Conservation International), Theodore Weller (U.S. Forest Service), Wayne Thogmartin (UMESC), Craig Willis (University of Winnipeg), and Brian Reichert (FORT)

White-nose Syndrome (WNS) has caused severe declines in bat populations over the past 10 years and colony sizes at winter hibernacula have decreased on average by >90% for three species (Myotis septentrionalis, Myotis lucifugus, and Perimyotis subflavus). These three species are listed as endangered in Canada. In the United States, M. septentrionalis was listed as Threatened under the Endangered Species Act (ESA) in 2016 (https://www.federalregister.gov/d/2016-00617)) and M. lucifugus and P. subflavus have been petitioned for listing.  These species are a top priority for monitoring and management attention based on their severe declines at hibernacula and regulatory status. 

We compiled winter counts of hibernating bats collected by a consortium of state and federal biologists at 222 sites across 25 states and provinces spanning 23 years from 1995-2018. This effort represents the most comprehensive dataset to date of winter colony counts of bats. These data are now integrated into the NABat Monitoring Program to allow current and future assessment of population impacts from WNS.  NABat was initiated in 2015 as the first broad-scale coordinated effort to monitor bat species across North America (Loeb et al. 2015). For most hibernating bat species, winter colony count data have been the most reliable data to measure WNS-related declines. However, some resource managers have expressed concern that internal surveys at hibernacula may have adverse effects on hibernating bats. Acoustic monitoring at cave entrances during spring emergence could provide NABat monitoring partners with a less invasive, low-cost alternative to internal counts for obtaining reliable indices of local abundance without the need to enter the hibernacula. 

Tightly clustered roosting bats

Little brown bat (Myotis lucifugus) in the Shipp Room, Hellhole cave

(Credit: Alan Cressler. Public domain.)

We will determine if acoustic activity following NABat protocols during spring emergence at hibernacula can be used as an alternative monitoring option at sites when counting hibernating bats is not feasible or desired. By collecting data at a continental scale (Fig. 1), we will develop the first systematic and quantitative accounting of hibernation phenology and duration, allowing for testing hypotheses related to survival and population persistence for vulnerable species.

Map showing 120 hibernacula with winter colony counts of Myotis lucifugus and Perimyotis subflavus

Figure 1.  (A) Map showing 120 hibernacula with winter colony counts of Myotis lucifugus and Perimyotis subflavus forming an initial sampling frame for site selection across the latitudinal gradient of WNS. (B) Example inset of a NABat GRTS cell with focal hibernaculum with a phenology detector and 4 sites selected for stationary NABat sampling in the surrounding landscape.

(Public domain.)