Bats of Richmond National Battlefield Park following white-nose syndrome: Public version

Abstract

I conducted bat surveys at Richmond National Battlefield Park to assess the status of bat communities following potential impacts of the disease white-nose syndrome. This disease, caused by the fungus Pseudogymnoascus destructans, has severely reduced populations of several bat species in the eastern United States, threatening some with regional extirpation. Most affected species include the little brown bat (Myotis lucifugus), northern long-eared bat (Myotis septentrionalis), Indiana bat (Myotis sodalis), and tricolored bat (Perimyotis subflavus). During the summers of 2016–2020, I sampled sites with acoustic bat detectors and conducted capture surveys using mist nets to characterize bat communities with a focus on documenting WNS-imperiled species. I also conducted non-reproductive, or dormant, season acoustic and capture surveys from 2017–2021, to investigate potential local wintering by bats, especially northern long-eared bats, which have recently been discovered wintering in the Coastal Plain of North Carolina. Acoustic results identified the presence of ten bat species by echolocation calls: big brown bat (Eptesicus fuscus), eastern red bat (Lasiurus borealis), hoary bat (Lasiurus cinereus), silver-haired bat (Lasionycteris noctivagans), little brown bat, northern long-eared bat, Indiana bat, evening bat (Nycticeius humeralis), tricolored bat, and Mexican free-tailed bat (Tadarida brasiliensis). Capture surveys documented big brown bats, eastern red bats, silver-haired bats, and evening bats. To examine habitat associations of bat species, I used generalized linear mixed models of a selection of variable candidates: habitat type, distance to water, minimum nightly temperature, and nightly precipitation to predict summer activity. Activity of big brown, eastern red, hoary, and Mexican free-tailed bats was highest in open habitats. Myotis spp. were most associated with mixed forest habitats. Tricolored bat activity was highest and evening bat activity was lowest in riparian and wetland habitats. To examine seasonality in bat species occurrence, I modeled acoustic activity in passes/night by Julian date using generalized additive models. Activity of big brown, eastern red, little brown, and tricolored bats was highest during summer. Activity of northern long-eared and Indiana bats was very low overall but was also highest in the summer. Tree bat species hoary, silver-haired, and Mexican free-tailed bat activity was highest in the spring and fall. Dormant season results suggest some winter occurrences for most bat species. Visual validation of echolocation calls revealed misidentifications were problematic for Myotis spp. little brown bat, northern long-eared bat, and Indiana bat, but diagnostic calls of all three species were recorded. Acoustic passes identified as northern long-eared bats suggest some individuals may be wintering nearby, but winter activity was very low and not indicative of large overwintering populations. An internal NPS version of this document that includes an appendix with capture survey site coordinates is available and may be requested as needed.