Jochen Jaeger

Associate Professor at Concordia University

The most important mitigation measure for reducing roadkill is wildlife fencing, because more effective measures are often unrealistic, whereas less expensive measures are ineffective. Mortality-reduction graphs can help prioritize road sections for fencing. Theoretically, fencing many short road sections requires less total fencing for the same predicted reduction in mortality than fencing a few long ones if the fences were 100-% effective. However, animals frequently move around the fence ends, which reduces the effectiveness of fences. The trade-off between the number of fence sections and the length of the fences has been called the Few-Long-Or-Many-Short (FLOMS) fences trade-off. How long is long enough for a fence to be effective? We developed a model for predicting the fence-end effect as a function of fence length (L). We consider four variations of the model and compare the predictions with empirical data. In their most basic form, the models predict effective fence-length as: Leff = L – R (Model A), Leff = L – 0.5 R (Model B), Leff = L – 0.4521 R (Model C), and Leff = L – 0.226 R (Model D), where R is the radius of the average home range size of the target species. We predict the minimum length of wildlife fencing that can be expected to be effective for various species. The results can be included in the calculation of mortality-reduction graphs to predict the effectiveness of fencing at reducing wildlife mortality. This approach will help planners design more effective and more efficient configurations of fencing.

Keywords: effective fence length, fence-end effect, FLOMS, roadkill, road mortality, road mitigation, wildlife fencing