Where wildlife and traffic collide: Roadkill rates change through time in a wildlife-tourism hotspot

Abstract

Understanding when and where roadkill is most likely to occur is vital to reducing wildlife-vehicle collisions. However, little is known about how roadkill rates change through time and whether or not the key influences on roadkill also change. Understanding changes in roadkill will facilitate the best implementation of mitigation measures. We aimed to determine how roadkill rates have changed between two distinct time periods and assess whether the spatial and temporal drivers of roadkill rates may have changed: with a view to informing taxon-specific mitigation strategies. We assess the spatial and temporal factors that influence road mortalities in two periods (1998–1999 and 2014) at the same site for multiple taxa. Bi-weekly surveys were undertaken from February to May 1998 and 1999 and again from February to June 2014. In total 2479 individual roadkill were recorded throughout the surveys, with 1.59 roadkill per km per month in the 1990s, increasing to 2.39 per km per month in 2014. Roadkill rates increased primarily with road speed limit with mortalities peaking at moderate (60–80 km/h) speeds, however, the structural complexity of roadside vegetation influenced roadkill rates for some taxa but not others. We show that roadkill rates have changed through time with shifts in both the temporal and spatial influences on these roadkill rates. These changes are likely associated with changes in the abundance of taxa and increased vehicle traffic. The spatial and temporal drivers of roadkill rates were found to be taxon specific, and although mitigation measures exist, assessment of their efficacy remains a priority.