Kristina Ernest (Biological Sciences)
Roads destroy, degrade, and isolate wildlife habitats. Despite the ecological importance of bats and the effect roads have on bats’ access to foraging, breeding, and roosting habitat, relatively few studies have investigated whether wildlife crossing structures (under- and overpasses) facilitate bat movements in road-fragmented areas in North America. Washington State Department of Transportation has created multiple wildlife crossing structures along Interstate-90 (I-90), a major highway near Snoqualmie Pass in the Cascades. We evaluated species presence and activity of insect-eating bats along I-90 where it intersects with wildlife underpasses to investigate whether bats preferentially cross the highway at crossing structures to avoid traffic. To monitor activity patterns and species composition of bats, we recorded echolocation calls at locations along the highway with and without underpasses and in adjacent forest habitats. We used statistical modeling to examine differences in bat activity between these site types. All bat species detected in the adjacent forest habitats were also detected along the highway. Total bat activity was higher near the highway than in the forest habitats, but did not differ between locations with underpasses and those without. Several factors other than the presence or absence of underpasses could explain these differences. However, our study provides baseline information on bats in the area. We recommend more intensive monitoring to better understand the effectiveness of crossing structures in reducing the impacts roads have on bats.
Keywords: Bat, Activity, Crossing structure, Interstate, Cascades, Acoustic monitoring