Carcass Persistence and Detectability: Reducing the Uncertainty Surrounding Wildlife-Vehicle Collision Surveys

Carcass persistence time and detectability are two main sources of uncertainty on roadkill surveys. In this study, we evaluate the influence of these uncertainties on roadkill surveys and estimates. To estimate carcass persistence time, three observers (including the driver) surveyed 114km by car on a monthly basis for two years, searching for wildlife-vehicle collisions (WVC). Each survey consisted of five consecutive days. To estimate carcass detectability, we randomly selected stretches of 500m to be also surveyed on foot by two other observers (total 292 walked stretches, 146 km walked). We expected that body size of the carcass, road type, presence of scavengers and weather conditions to be the main drivers influencing the carcass persistence times, but their relative importance was unknown. We also expected detectability to be highly dependent on body size. Overall, we recorded low median persistence times (one day) and low detectability (道路动物尸体留存时长与可探测性是道路致死调查中两大核心不确定性来源。本研究针对这两类不确定性对道路致死调查及估算结果的影响展开系统性评估。为估算动物尸体留存时长，研究团队由3名观察员（含驾驶员）组成，以汽车为观测载体，每月对114公里路段开展为期两年的跟踪调查，每次调查连续开展5天，全程搜寻野生动物车辆碰撞（Wildlife-Vehicle Collisions, WVC）事件遗留的尸体。为估算尸体可探测性，我们随机选取292段总长146公里的500米路段，由另外2名观察员以步行方式开展调查。我们推测，尸体体型、道路类型、食腐动物存在情况及天气条件是影响尸体留存时长的主要驱动因素，但其相对重要性尚不明确；同时我们认为，尸体可探测性高度依赖于尸体体型。总体而言，本次调查记录到的尸体留存时长中位数较低（仅1天），且可探测性偏低（