Road mortality of water snakes in active versus protected floodplains in light of landscape structure and traffic volume in north-eastern Hungary

Abstract

Abstract Flood protection measures can have large impacts on ecosystems and their biodiversity, yet direct comparisons of active and inactive floodplains are rare. We compared the number of roadkilled individuals of two semiaquatic water snakes (Natrix natrix and N. tessellata) on 58 km of road sections bordered either by an active floodplain or a flood-protected former floodplain in NE Hungary based on surveys conducted once every two weeks in three years. We found unexpectedly high road mortality of snakes, which was rather similar across years. Mortality had a spring and an autumn peak, corresponding to the times when snakes emerge from and return to hibernating sites. Road mortality was more severe and more predictable in the flooded than in the flood-protected area, even though traffic was more intense in the latter. Our results show that small-scale spatial differences in road mortality are mediated by landscape structure along the road, while the effects of traffic intensity and the age and sex of the individuals were negligible. For conservation implications, our study suggests that establishing culvert passages under the road and artificial hibernating sites on the floodplain-side of the roads in critical sections to reduce the road-related mortality.