Extrapolated Offshore Occupancy Predictions for Three Bat Species

We generated an extrapolated surface of predicted occupancy values offshore for the little brown bat (Myotis lucifugus), northern long-eared bat (Myotis septentrionalis), and tri-colored bat (Perimyotis subflavus). Values were generated for each grid cell in the Continental United States (CONUS) Grid-Based Offshore Sampling Frame which extends from coastal areas (i.e., 10 kilometer [km] x 10 km grid cells that line the coastline) out to the Exclusive Economic Zone (Cox et al., 2022). Using land based occupancy predictions from the most recent North American Bat Monitoring Program (NABat) status and trends products (Udell et al., 2022; Udell et al., 2023; Wray et al., 2024), we used a kernel-based extrapolation with an exponential decay function to estimate species-specific occupancy from coastal grid cells to the Exclusive Economic Zone boundary. Occupancy predictions used for extrapolation represent occupancy probabilities in the pre-volancy season in the summer (May 1–July 15) averaged across 2017–2022 for northern long-eared bat and tri-colored bat, and the entire summer (May 1–August 31) from the most recent prediction year available for little brown bat. Each model also included a winter-to-summer connectivity metric to incorporate spatiotemporal influences of known winter range on summer occupancy. We used the mean documented dispersal distance for each species of interest as the maximum distance (Cockrum 1956, Fenton 1970, Griffin 1945, Griffin 1940, Nagorsen and Birgham 1993, Norquay et al. 2013, White et al. 2017) at which an extrapolated prediction could be made. We also calculated credible interval widths for each of the three species for each grid cell along the coastal shoreline as a measure of uncertainty using the upper and lower credible intervals from Udell et al., 2022, Udell et al., 2023, and Wray et al., 2024.