Wildlife crossing structures are proven to be successful at passing a variety of species safely across the road however these structures are unlikely to be used as frequently or by the entire suite of local species, perhaps because of the presence of vehicle traffic on the road. We evaluated the effect of traffic on wildlife use of a crossing structure in Wilsonville, Oregon, USA, by comparing wildlife tracks on sand track pads for summers during three two-year time periods: after the road was initially opened, when it was closed to traffic, and after it was re-opened.
Results/Conclusions
Initial data explorations show that average weekly detections of animals increased during the road closure years compared with the periods before the closure and with the period after the road re-opened. Individual species showed variability in their response with the majority of species detections peaking during closure (coyote, deer mice, rabbit, tree frog), decreasing during closure (vole) or showing a pattern of detection that appears to be independent of road closure status (Columbia black-tailed deer, striped skunk, mink). While additional factors, such as changes in vegetation and surrounding land use are likely influencing species activity and detection at the Boeckman Road crossing structure there is nonetheless a clear positive response in the wildlife community when traffic is absent but the physical structure of the road remains. Hence, our findings suggest that many wildlife species demonstrate avoidance behavior and are less active in under-road passages when there is traffic on the roads above, even for mainly nocturnal species, which could partially limit the utility of crossing structures for habitat connectivity. Demonstrating that a complete lack of traffic resulted in increased species activity, additional experimental work investigating the impacts of a range of traffic volumes would further our understanding of how species respond to the presence of vehicles and inform mitigation decisions that could reduce the barrier effect of roads.