Bats of Colonial National Historical Park following white-nose syndrome

Abstract

I conducted bat surveys at Colonial National Historical Park to assess the status of bat communities following potential impacts of white-nose syndrome (WNS) since its arrival in Virginia in 2009. 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. In the East, 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 in Yorktown and Jamestown Island with acoustic bat detectors from the spring of 2019 through the spring of 2021 and conducted capture surveys using mist nets in 2019 and 2021 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 COLO, especially northern long-eared bats, which occur year-round in the Coastal Plain of North Carolina. Acoustic results identified the presence of eleven bat species by echolocation calls: big brown bat (Eptesicus fuscus), eastern red bat (Lasiurus borealis), hoary bat (Lasiurus cinereus), silver-haired bat (Lasionycteris noctivagans), southeastern bat (Myotis austroriparius), little brown bat, northern long-eared bat, Indiana bat, evening bat (Nycticeius humeralis), tricolored bat, and Mexican free-tailed bat (Tadarida brasiliensis). Acoustic results included diagnostic echolocation calls of little brown, northern long-eared, and Indiana bats, however, presence should be interpreted with caution due to similarities of call structures among Myotis spp. bats. Capture surveys documented seven species: big brown, eastern red, hoary, silver-haired, southeastern, evening, and tricolored 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 by significant predictors. Activity of hoary, silver-haired, little brown, evening, tricolored, and Mexican free-tailed bats was highest in open habitats. Big brown bat and Indiana bat identifications were most associated with forest habitats. Eastern red bat activity was high in both forest and open sites. Southeastern bat activity was highest in wetland sites and was largely confined to these habitats. Northern long-eared bat activity was not significantly different among habitat types. 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, hoary, little brown, northern long-eared, tricolored, evening, and Mexican free-tailed bats was highest during summer. Silver-haired bat activity was highest in March indicative of seasonal migration. Hoary and Mexican free-tailed bat also exhibited high activity on several nights in the spring suggestive of migratory movement. Dormant season results suggest some winter occurrence for all identified bat species except Indiana bats. Very few characteristic calls of northern long-eared bats were observed from December through February, suggesting they winter locally in far lower abundances than in the Coastal Plain of North Carolina to the south.