Bats of Petersburg National Battlefield following white-nose syndrome

Abstract

I conducted bat surveys at Petersburg National Battlefield Park (PETE) 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), the federally-endangered northern long-eared bat (Myotis septentrionalis) and Indiana bat (Myotis sodalis) (USFWS 2007, USFWS 2022a), as well as the tricolored bat (Perimyotis subflavus), which has been proposed for endangered status (USFWS 2022b). I sampled sites with acoustic bat detectors from the summer of 2016 through fall 2021 and conducted capture surveys using mist nets from 2016-2019 to characterize seasonal occurrence of bat species with a focus on documenting WNS-imperiled species. Surveys also sought to document potential over-wintering of bats at PETE, especially northern long-eared bats, which have recently been discovered wintering in the Coastal Plain of North Carolina. Acoustic results identified the presence of nine 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, Indiana bat, evening bat (Nycticeius humeralis), tricolored bat, and Mexican free-tailed bat (Tadarida brasiliensis). Northern long-eared bats were identified acoustically by software, but identifications were invalidated by visual review. Acoustic misidentifications also occurred for little brown and Indiana bats, but diagnostic calls were confirmed. Capture surveys documented big brown bats, eastern red bats, evening bats, and a single little brown bat. 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, hoary, silver-haired, and Mexican free-tailed bats was highest in open habitats. Little brown and eastern red bats were most associated with mixed forest habitats. Evening bat activity was highest in deciduous forests. Habitat type was not a significant predictor of activity for Indiana and tricolored bat activity. 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, tricolored, and evening bats was highest during summer. Activity identified as Indiana bats was very low overall but was also highest in the summer. Activity of tree bat species hoary, silver-haired, and Mexican free-tailed bat was highest during the dormant season and peak activity appeared associated with migration. Dormant season results suggest some winter activity for most bat species identified as present in the park.