Forage resource partitioning of Appalachian bats at the Radford Army Ammunition Plant in Radford, Virginia

Background/Question/Methods

Insectivorous bats are important pest control in North America, however their populations have been declining due to white-nose syndrome, wind-turbine collisions, and habitat loss. The US Department of Defense (DoD) is a large federal landholder charged with balancing military training and biodiversity conservation and provide habitats for a large number of threatened and endangered species. For land managers to effectively conserve bat populations and maintain environmental compliance, robust estimations of species occurrence, distribution, and habitat use are needed. The Radford Army Ammunition Plant (RFAAP), in Southwest Virginia, potentially hosts 12 bat species. The objectives were to relate foraging habitat variables (canopy cover, forest density) and spatial partitioning of bats across the RFAAP. Remote ultrasonic bioacoustics monitors (Wildlife Acoustics) were deployed to record bat echlocation. Thirty-two survey locations were stratified by major physiognomic habitats and sampled to avoid temporal and spatial pseudoreplication. Units recorded for 7-14 nights (total 264) at each location from 02 June – 11 August 2020. A ten-factor wedge prism was used to measure basal area, and a convex spherical crown densiometer to estimate canopy cover. Acoustic analysis followed US Fish and Wildlife Service guidelines for Indiana bats using Kalidoscope pro v4.2, BCID 2.8d, and hand verifications.

Results/Conclusions

We acoustically detected nine bat species at RFAAP and summarized the number of calls correctly classified into a nightly activity index for each species. Silver-haired bats (Lasionycteris noctivagans) and Big brown bats (Eptesicus fuscus) were the two most active species at RFAAP (X̄= 12.7, 8.4 calls/night, respectively), In addition, we documented the endangered Gray bat (Myotis grisescens, 0.64 calls/night), and two Virginia Species of Greatest Conservation Need, Little brown bat (Myotis lucifugus, 4.5 calls/night), and Tri-colored bat (Perimyotis subflavus, 1.6 calls/night). Activity was equated to measured habitat variables using a generalized linear model approach. Canopy cover measurements ranged from 0-98% and basal area ranged from 0-20 stems per acre across the survey locations. As canopy cover/density decreased, the presence of open-adapted foraging species (Big brown bat; and Hoary bat; Lasiurus cinereus) increased. As canopy cover/density increased, the presence of clutter-adapted foraging species (Eastern red bat Lasiurus borealis; and Evening Bat; Nycticeius humeralis) increased. Determining species preference for basal area and vegetative cover will assist RFAAP natural resource managers facilitate effective land management practices to promote bat foraging behaviors and mitigate potential impacts.