Danger under wheels: mammal roadkills in the threaten lowland Atlantic Forest in southeast Brazil

Understanding the ecological impacts of roads on mammals requires periodic monitoring of roads, and identification of both temporal and spatial distribution of roadkills (i.e., roadkill hotspots). The main aim of the study was to identify the most roadkilled mammals and evaluate the temporal and spatial distribution of roadkills in the RJ-122, a highway that crosses the threaten lowland Atlantic Forest in the state of Rio de Janeiro, southeast Brazil. Between October 2017 and January 2020, an intense monitoring study was conducted, with the carcasses of the roadkilled mammals being collected three times a week. Overall, we recorded 295 roadkilled mammals belonging to 22 species, resulting in 11 roadkills per month for the RJ-122 highway. The black-eared opossum, Didelphis aurita (N= 149, 51%) stood out as the most roadkilled mammal, followed by porcupine, Coendou spinosus (N= 24, 8%), crab-eating fox, Cerdocyon thous (N= 23, 8%), nine-banded armadillo, Dasypus novemcinctus (N= 23, 8%), and white-tufted marmoset, Callithrix jacchus (N= 20, 7%). Roadkills on the RJ-122 varied throughout the year, being more frequent in the rainy season (N= 180) than in the dry season (N= 115), and were concentrated in two hotspots, indicating some critical points with high roadkill frequency. Hotspots were associated with areas with dense natural vegetation, which can function as forest corridors in this fragmented landscape. Based on our results, several mitigation measures are recommended for the RJ-122 highway.