Ungulate substrate use in fauna passages

Fauna passages are increasingly constructed at major roads and railways to mitigate the negative effects of infrastructure and traffic on wildlife. The function of such passages depends on design, including the construction materials, soil, and vegetation. Providing ‘naturalness' in fauna passages may entail significant costs, yet its benefits are unclear. By using camera trap data, we examined ungulate (moose Alces alces , roe deer Capreolus capreolus , reindeer Rangifer tarandus tarandus , and white‐tailed deer Odocoileus virginianus ) substrate use in seven passages serving both fauna and local roads (overpasses) and fauna and watercourses (underpasses) in boreal Sweden and Finland. While all substrates were used, during snow‐free periods, the general pattern was that ungulates used smoother surfaces (fine‐grained topsoil, grass, artificial fiber mat, and dirt road) more than expected based on their availability. Coarser surface (stony/rocky ground), shrub, and water were used less than expected. The