Use and Effectiveness of Wildlife Crossing Structures with Short Sections of Wildlife Fencing

Our growing transportation infrastructure in the United States has many direct and indirect impacts to wildlife populations. Humans are also impacted by the interaction of roads and wildlife in terms of wildlife-vehicle collisions (WVC’s); which annually result in: hundreds of human fatalities, tens of thousands of human injuries, and billions of dollars in property damage. In response to concerns for wildlife and human safety, road mitigation measures are becoming an increasingly important tool for transportation agencies to minimize the risks of WVC’s. The construction of multiple wildlife crossing structures in combination with wildlife fencing have been shown to reduce WVC’s by over 80% where extensive continuous wildlife fencing (covering many miles) has been implemented, and by 50-60% in areas where more limited fencing (covering 1-3 miles) has been implemented. In areas where land use is dominated by humans (agriculture, housing, access roads, etc.) such mitigation measures are not always possible or desirable. This results in a push towards more isolated crossing structures with little to no wildlife fencing to provide frequent road access and preserve landscape aesthetics. The effectiveness of isolated crossing structures with short sections of fencing (only a few hundred meters or less) is not well documented in terms of potential WVC reduction or wildlife use of the structures. In this study I investigate: the use of isolated crossing structures and fence ends by target species, the effect of fence length on at-grade crossings, and the ability of short sections of fencing to keep wildlife off the road. Overall, 82% of wildlife used the crossing structures for crossing as opposed to going around fence ends. Over the length of fence lengths sampled (3m-256m) there was no relationship between fence length and the number of crossings at fence ends. Deer were often foraging at fence ends, with nearly half of all foraging events occurring in the right of way (closer to the road than the fence is/would be). Overall, deer generally choose to use the crossing structures to get to the other side of the road, but they will still often be present in the right of way where they are not excluded with fencing. This indicates that while isolated crossing structures with short fencing may provide wildlife safe access to habitat on either side of the road, they may not provide the desired reduction in WVC’s