If the goal for mitigation is merely to stop animals from being killed on roads, then fencing is a potential solution, and one which is popular with a public concerned by the toll that wildlife-vehicle collisions are taking on motorists. A 2016 study by Rytwinski et al.4 on the effectiveness of road mitigation at reducing roadkill produced a meta-analysis of 50 studies that evaluated different types of mitigation measures. Findings indicated that fences, either implemented alone or as buffers around wildlife crossing structures such as overpasses, reduce roadkill by 54%, compared to unmitigated control areas. Fences are not an ideal solution, however, for many reasons. Fences are expensive to install and maintain, and people are sometimes opposed to fences for the aesthetic reasons of wanting their scenic drives to appear wilder3. If they are to be implemented correctly, planners have to consider length, height, mesh size, whether an animal can dig under the fence, how to deal with the inevitable fence-end issues, and what level of yearly maintenance is needed to reduce replacement costs4,5. Short fences less than 5 km in length are less effective at reducing collisions than long fences6, resulting in higher incidences of roadkill at fence ends which wildlife are more likely to find and use over shorter distances than over longer distances4.
If the goal for mitigation is to stop animals from being killed on roads and to allow wildlife to move freely, then fencing on its own is not enough.