Urban wildlife use of existing highway crossings and access points
Roads and traffic are a significant source of mortality for many wildlife species and compromise habitat integrity. Despite widespread recognition that maintaining or restoring wildlife population connectivity is the single most effective mitigation measure for species conservation, roads and highways are rarely designed or modified to facilitate safe wildlife crossing. Understanding wildlife reactions to roads and existing crossing structures is critical for the development of effective conservation programs, minimizing property damage, and reducing human casualties caused by vehicle collisions. Here, we used camera arrays to quantify the extent to which six common mid- to large-bodied mammals associated with near urban environments used safe (i.e., underpasses and culverts) and risky (i.e., gaps in fencing which allow wildlife direct highway access) passages to cross a high volume, 8-lane Interstate highway in a major metro area. We then analyzed spatial and temporal variation in species-specific detection or risky movements. Our results suggest preferences that vary by species and crossing type, and though raccoons, gray foxes and coyotes were more likely to be detected at safe crossings than unsafe crossings, nearly all study species were frequently detected at unsafe crossings near the highway. Our research illustrates the diversity and frequency of wildlife using the land on the highway edge, helping explain why this section of highway has some of the highest incidence of wildlife-vehicle collisions in California. To make the highway safer for both wildlife and drivers, we suggest sturdy and well-maintained exclusionary fencing in conjunction with modification of already-available crossing structures (culverts and underpasses) for use by wildlife.