Document Type

Thesis

Date of Degree Completion

Spring 2022

Degree Name

Master of Science (MS)

Department

Biology

Committee Chair

Kristina Ernest

Second Committee Member

Clay Arango

Third Committee Member

Allison Scoville

Abstract

Roads force wildlife to navigate degraded and fragmented habitats across the globe, creating barriers to movement and increasing the risk of mortality. This includes bats, whose movements between foraging and roosting habitats may be impeded by roads. Wildlife crossing structures (WCS) are a common mitigation strategy to increase connectivity, but investigation into bat activity in and around these structures is limited. I investigated bat species presence and activity along Interstate-90 in the Cascade Range of Washington State. My goal was to test whether all bat species found in the nearby forest were also active along the highway, and whether bat activity levels were higher at highway locations with WCS than at locations without underpasses. Echolocation calls were recorded at locations with and without underpasses, and in the adjacent forest. Calls were analyzed across all species and separated into 4 guilds based on species-specific frequency ranges. All 8 species detected in the forest were also detected along the highway. Total bat activity was higher along the highway than the adjacent forest but did not differ between locations with vs. without underpasses. Activity for three of the four guilds followed similar trends, but the 50-kHz guild showed significantly higher activity at underpasses than at locations without them. Confounding variables make interpretation challenging, but this study provides important information on bat activity along an interstate highway in Washington State. I highlight the need for more intensive monitoring efforts to better understand the effectiveness of WCS in reducing the impacts roads have on bats in North America.

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