Interstates, highways, roads – these all act as barriers to movement for plants and animals. Efforts to build underpasses and overpasses in places such as Banff National Park or the Netherlands wildlife have helped keep large animal populations connected and reduced wildlife-vehicle collisions. While these wildlife crossings are often surrounded by fencing to funnel individuals safely, there is little guidance for managers on how long to make the fencing and how effective it may be.
A recent study by Huijser et al. looks at fencing length around wildlife crossing structures in western Montana to better understand how different management approaches might influence wildlife-vehicle collisions and provide safe passage for large mammals. Through a combination of camera traps at crossing structures and a review of past literature, the study shows a striking difference in the effectiveness of fencing as it gets longer. When fencing was at least 5 km long, there was an 80% reduction in vehicle-wildlife collisions. Shorter fences were less effective overall and more variable in their effectiveness, and the fencing location and use of fence-end treatment make an impact on effectiveness.
Several management recommendations emerge from the study:
- Including wildlife fencing when designing highways and crossing structures can have a large impact on vehicle collisions and the probability of animals moving safely across.
- If the primary goal of an underpass is to reduce collisions with large wild mammals (ungulates in particular), then fencing should be at least 5 km long.
- Short sections of fencing can be more effective in reducing collisions when fence-end treatments are included, and when fencing covers collision hotspots and adjacent buffer zones.
- Use of the crossing structure is highly influenced by location, and although longer fence lengths don’t guarantee greater use, a well-placed crossing structure with long fencing can have a large impact.
Huijser, M. P., E. R. Fairbanks, W. Camel-Means, J. Graham, V. Watson, P. Basting, and D. Becker. 2016. Effectiveness of short sections of wildlife fencing and crossing structures along highways in reducing wildlife-vehicle collisions and providing safe crossing opportunities for large mammals. Biological Conservation 197: 61-68.