Importance of professional roadkill data in assessing diversity of mammal roadkills

With considerable under-reporting of roadkills, the impact of transport on biodiversity is mostly underestimated. The main goal of this study was to compare official roadkill records with data collected by professional biologists. On roads with different traffic intensities, we compared species richness, diversity indices and species composition with regard to the data sources and performed roadkill hotspot analysis. Biologists recorded more mammal species killed, a higher diversity index and a different composition of dominants in the roadkills, as well as different numbers and locations of hotspots. Traffic intensity and population size explained 63-93% of the variation in roadkill numbers in ungulates. Professional monitoring effort and traffic intensity explained nearly 90% of variation in roadkill numbers, 70% of variation in recorded species and 40% of diversity variation. With greater accuracy than available official data, professional roadkill diversity data should be used in wildlife-vehicle accident analysis and in planning road safety infrastructure.