Spatial occupancy patterns of the endangered northern long-eared bat in New England

Abstract

Aim: White-nose syndrome has caused severe declines in eastern North American cave bats, leading to the federal listing of the northern long-eared bat (Myotis septentrionalis) as endangered in the United States and Canada. This has heightened the importance of long- term monitoring to inform species status assessments. We employed a combination of long-term repeated and single- eason acoustic survey data to assess the regional presence, spatial distribution, occupancy, and detection probability of northern long- eared bats. Location: New England, United States. Methods: We analysed acoustic data from 2357 detector sites, aggregated by year, using Bayesian single-species occupancy models. We investigated the influence of habitat characteristics, climatic variables, and year (2015–2022) on occupancy and the effects of weather conditions and survey month (May to August) on detection probability. Spatial random effects were included to address residual spatial autocorrelation, with a 1-km resolution chosen based on significant positive autocorrelation observed in a non- spatial model. Results: Occupancy was highest on steep, forested hillsides with minimal anthropogenic development, higher in warmer regions, particularly along coastlines and on offshore islands, and declined across survey years. Including a 1-km spatial random effect reduced residual autocorrelation and suggests northern long- eared bats utilise resources at small to medium landscape scales. Detection probability was highest earlier in the maternity season, but declined when monthly precipitation or temperature exceeded average conditions. Conclusions: Conservation efforts that focus on steep, forested hillsides in warmer regions with low anthropogenic development could be beneficial. Our analysis supports the use of spatial random effects at a 1-km2 scale, highlighting the importance of survey designs that capture ecological variation at species- specific resolutions. Additionally, early- season acoustic surveys conducted during favourable weather conditions may improve monitoring effectiveness. Acoustic sampling and spatial occupancy modelling offer powerful tools for monitoring remnant populations of northern long-eared bats and guiding conservation practices.