Macropod roadkill: a citizen science evaluation of the effectiveness of virtual fencing and reducing posted speed limits on a local road

Roadkill across Australia is a significant issue, with estimated annual rates in the millions, resulting in substantial costs to society. Records of macropod roadkill collected by citizen science wildlife-rescue volunteers were obtained from iNaturalist for a 32-month period on a New South Wales south coast local road. These data were used to assess whether mitigation measures, including a virtual fence (VF) and reduced speed limits, decreased roadkill. Previous studies of VF effectiveness have found no significant reduction in wallaby roadkill on higher speed-limit roads. In contrast, eastern grey kangaroos (Macropus giganteus) were the main roadkill in this study and roadkill reductions of approximately 40–60% were recorded after a VF was installed and speed limits were 60 km/h or less, although only a short section showed a statistically significant effect. Sections with no mitigation measures or with changes to speed limits alone, showed random variability. The results suggest that VF may reduce eastern grey kangaroo roadkill in hotspots when combined with speed limits of 60 km/h or less. However, the study highlighted the challenges and limitations of citizen science studies that do not have the proper design, controls, and the more sophisticated statistical analysis of scientific research projects.