Highway widening and underpass effects on vertebrate road mortality

Road widening (a.k.a. road dualling) and the presence of mitigation structures may have opposing effects on the number of animal-vehicle collisions. Their influence in tropical areas is poorly quantified, and we know little about how modifications of road structure affect fauna roadkill and mitigation. We evaluated how road widening and proximity to a wildlife underpass affect roadkill of medium and large mammals, using roadkill records from before and after the widening of 150 km of road with new and old wildlife underpasses. Roadkilled species were divided into three groups based on mobility and sensitivity to human disturbance. Four out of 16 species exhibited significantly higher roadkill after widening. Roadkill near underpasses was generally higher than by chance, despite our expectation of reduction of roadkills. This result indicates that we must adopt more effective mitigation measures, such as appropriate fencing combined with underpasses.

道路拓宽（又称道路复线化）与生态缓解设施（mitigation structures）的布设，可能对动物-车辆碰撞事故的发生数量产生相反影响。目前此类措施在热带地区的影响尚未得到充分量化，学界对道路结构改造如何影响野生动物路杀（roadkill）及相关缓解措施的成效亦所知有限。本研究依托一段150公里道路拓宽工程实施前后的路杀监测记录（该路段配有新旧野生动物下穿通道（wildlife underpass）），评估了道路拓宽以及与野生动物下穿通道的距离对大中型哺乳动物路杀事件的影响。研究团队依据各物种的移动能力与对人类干扰的敏感性，将16种受测路杀物种划分为三组。结果显示，16个物种中有4个在道路拓宽后路杀事件显著增多。尽管我们原本预期下穿通道附近的路杀事件会有所减少，但该区域的路杀率普遍高于随机概率水平。这一结果表明，亟需采用更为有效的生态缓解措施，例如将适配的围栏与下穿通道相结合的方案。