Forest characteristics predict tri-colored bat activity within novel Colorado habitats

Climate change and other anthropogenic pressures are altering species distributions. Several studies have indicated that tri-colored bats (Perimyotis subflavus) are extending their distributional range westward in the United States. Montane and subalpine habitats consist of a mosaic of forest types including lodgepole pine woodlands and montane meadows, which provide an opportunity to study how a newly arriving species, typically associated with lowland riparian systems, is adapting to novel environmental conditions. The objective of this study is to document tri-colored bat activity in these novel habitats using acoustic surveys and to quantify what factors are influencing activity patterns in habitats and at elevations not previously documented. We selected sites at 2700m elevation that differed in stand structure, driven primarily by beetle kill outbreaks, and were in various stages of secondary succession. We used acoustic monitoring to model habitat activity patterns using nonparametric multiplicative regression. Results showed that tri-colored bats used meadows and lodgepole pine stands undergoing secondary succession following bark beetle outbreaks. Activity was highest in meadows and early time-since-kill (TSK) forests in the beginning of the survey period, and tri-colored bats had increased activity in late TSK forest habitats at the end of the survey period in early August. Temporally, activity was lowest during the middle of the survey period (mid-July) indicating that tri-colored bats moved away from our study area. However, activity significantly returned by the end of the survey. Our study demonstrates that tri-colored bats are not restricting their activity to lower elevation riparian areas in the Colorado foothills, but instead appear to be using high elevation habitat types in areas dominated by lodgepole pine and subalpine meadows. We hope this study will support conservation efforts for this species following the proposed U.S. Fish and Wildlife Service listing.