From roadkill monitoring to evidence-based wildlife mitigation in the Brazilian Pantanal

Wildlife-vehicle collisions (WVC) are a major threat to biodiversity conservation and human safety, particularly in tropical regions with high wildlife diversity and expanding transportation networks. Despite growing efforts to reduce road impacts on wildlife, there is still limited evidence evaluating the effectiveness of large-scale mitigation strategies in tropical wetlands. Here, we evaluated the spatial and seasonal patterns of wildlife road mortality and assessed the effectiveness of wildlife underpasses and associated fencing along 280 km of the BR-262 highway in the Pantanal–Cerrado ecotone, Brazil. Roadkill monitoring conducted over six years recorded 9,157 individuals from 238 vertebrate species, including 17 threatened species. Reptiles and mammals were the most frequently recorded taxa, with Caiman yacare, Dasypus novemcinctus , and Cerdocyon thous presenting the highest mortality rates. Using a Before-After-Control-Impact (BACI) design, we found that long fenced sections reduced road mortality of Caiman yacare by 70.4%, whereas no significant reductions were detected for Cerdocyon thous and Hydrochoerus hydrochaeris . Spatial analyses identified 589 overlapping roadkill hotspots, providing the basis for prioritizing mitigation measures in the most critical sections for medium- and large-bodied mammals, which are predominantly threatened species and are also associated with the most severe collisions involving road users. Based on these results, a large-scale mitigation plan was developed incorporating 170 km of fencing, 44 existing bridges, 22 existing underpasses, 10 new wildlife underpasses, seven artificial canopy bridges, six speed traps, eight jump-outs, and 36 rumble strips. Our findings provide one of the most comprehensive evaluations of wildlife mitigation planning in a tropical wetland ecosystem and offer a scalable framework for wildlife-friendly transportation infrastructure in biodiversity-rich regions worldwide.