Spatial distribution of wildlife road mortality: How important is rigorous data collection?

• We identified hotspots and coldspots at four scales for three confidence levels. • We compared rigorously collected data to data collected by highway patrol personnel. • We found considerably more animals and identified more species than highway patrol. • Rigorous surveys provide a better understanding of impacts of roads on biodiversity. • Installation of fences combined with designated wildlife passages is needed. We conducted 66 road mortality surveys along a 31.5 km stretch of a high-traffic 4-lane highway between Montreal and Sherbrooke in Québec, Canada. Surveys by vehicle between May and August 2019 recorded 212 animal carcasses from 48 species. Hotspots and coldspots for ground-dwelling vertebrates (mammals, amphibians, and reptiles) and birds were identified at four scales. The number of hotspots was higher at finer scales, while the combined length of hotspots was greater at coarser scales. We found significantly more animals and identified more species than the highway patrol, suggesting that rigorous road mortality surveys are beneficial for better understanding road impacts on biodiversity. We estimated that the highway patrol’s reporting probability for medium-sized mammals (more than 0.65 kg, less than 30 kg) was between 21 % and 54 % that of our systematic surveys. We recommend priority locations for mitigation to reduce road mortality and re-establish connectivity between wildlife populations separated by the highway.