The distribution of vertebrate roadkill varies by season, surrounding environment, and animal class

Abstract

Due to rapid human expansion in the last century, wildlife roadkill is becoming a concerning threat to biodiversity and human safety. The frequency of roadkill events depends on factors related to specific traits of the road—tortuosity or the presence of fences, among others—and the animal ecology—such as activity patterns, reproductive season, or thermoregulation. These, in turn, are related to environmental factors, with seasonal variations. Here, we assessed roadkill mortality of terrestrial vertebrates over the year. To do this, we sampled 10 road sections (of 3 km, by walk) in the south of Spain for a full year, registering the carcasses of run-over vertebrates. Then, we analysed the spatiotemporal patterns of roadkill events for the four vertebrates’ classes and the effects of road traits (presence of fence, tortuosity, distance to water point) and environmental variables (mean temperature and precipitation). Mammals suffered the highest mortality by roadkill (45.72%). The frequency of collisions was independent of tortuosity, presence of fences, and precipitation, while mean temperature significantly increased the probability of collision of mammals, birds, and reptiles. There was a seasonal effect in the number of collisions, which spatial pattern depended on the class of vertebrates. All this leads us to conclude that, to reduce the impact caused by roadkill mortality on wildlife, we need specific measures to be taken timely in each critical place and for each vertebrate group.