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Context Accurately estimating wildlife roadkill is necessary to compare different roads, periods, and species, and to plan and assess mitigation effectiveness. We must account for the two main sources of errors associated with carcass sampling – carcass detection and persistence. Open-population models are used to estimate abundance, survival probabilities, and recruitment in living animal populations, accounting for imperfect detection, and they can be used in the context of animal fatalities. Aims The aim of this study was to explore an open-population approach to estimate comparable roadkill rates from carcass capture–recapture data, accounting for carcass detection and persistence. Methods We surveyed carcasses of the white-eared opossum (Didelphis albiventris) and black-and-white tegu lizard (Salvator merianae) on four road stretches using two sampling designs with different number of visits and sampling sessions. Carcasses were marked to be recaptured over visits within the same sampling session, resulting in a capture history for each carcass. Encounter history data were modelled using the superpopulation formulation of the open-population capture–recapture model under Bayesian inference for different datasets. A daily roadkill rate per kilometre was derived from the model entry probability estimate. Key results We estimated a daily roadkill rate with 1501 captures from 447 opossum carcasses and 511 captures from 218 tegu carcasses. For full data, mean carcass detection over the sessions ranged from 0.49 to 0.85 for the opossum and from 0.27 to 0.80 for the tegu, and mean carcass persistence ranged from 0.60 to 0.94 for the opossum and from 0.64 to 0.91 for the tegu. Scenarios with more occasions and captures increased precision of roadkill rates. Conclusions We were able to explicitly estimate roadkill rates using an open-population capture–recapture model under a Bayesian framework. It provides accurate roadkill numbers for a known time frame and road extension, accounting for imperfect detection and its associated uncertainty. Under scenarios of few carcasses, users should consider a higher number of occasions. Implications Not addressing carcass sampling errors or simplistically addressing them (e.g. only once during the study period) could mislead mitigation efforts. The approach used here can be used to estimate fatalities in other locations, such as windfarms and powerlines, for which repeated observations of marked carcasses are an option.

Environmental licensing is a political tool to protect the environment and encourage sustainable development. Environmental Impact Assessments (EIAs) are the important document for impact assessment of activities during environmental licensing, and all decision-making process and effectiveness depend on its quality. Road construction, paving and widening require the approval of an EIA, since these activities are responsible for a large number of environmental impacts. Here we present an analysis of 16 EIAs of Brazilian roads, considering the impacts on terrestrial and aquatic fauna. We discuss if theimpacts recognized in road ecology literature are identified and assessed in these studies, if mitigation actions are based on information presented on the EIA, and the quality of road mortality assessment. We based the analysis on a checklist of road impacts and on scores calculated based on a set of criteria. We calculated relative scores for each EIA and for each type of impact across all studies. EIA quality was low (more than half EIAs had relative equal score or less than 50%); the studies analyzed poorly addressed the impacts recognized in the academic literature. The presence of impacts was not coherent along different sections of the EIA (baseline studies, impact matrix and proposition of mitigation measures). In 27.63% of cases the impacts were not present in any section of the EIA. In some situations, the impact was present in the baseline studies, but not in impact matrix or mitigation propositions, and in half of the situations analyzed the relative scoreof EIAs was lower than 30% for the quality of road mortality impact assessment. We recommend the improvement of the terms of reference should be a priority to enforce the elaboration of enhanced quality studies. A Portuguese version of this manuscript is available on request.

Environmental licensing is a political tool to protect the environment and encourage sustainable development. Environmental Impact Assessments (EIAs) are the important document for impact assessment of activities during environmental licensing, and all decision-making process and effectiveness depend on its quality. Road construction, paving and widening require the approval of an EIA, since these activities are responsible for a large number of environmental impacts. Here we present an analysis of 16 EIAs of Brazilian roads, considering the impacts on terrestrial and aquatic fauna. We discuss if theimpacts recognized in road ecology literature are identified and assessed in these studies, if mitigation actions are based on information presented on the EIA, and the quality of road mortality assessment. We based the analysis on a checklist of road impacts and on scores calculated based on a set of criteria. We calculated relative scores for each EIA and for each type of impact across all studies. EIA quality was low (more than half EIAs had relative equal score or less than 50%); the studies analyzed poorly addressed the impacts recognized in the academic literature. The presence of impacts was not coherent along different sections of the EIA (baseline studies, impact matrix and proposition of mitigation measures). In 27.63% of cases the impacts were not present in any section of the EIA. In some situations, the impact was present in the baseline studies, but not in impact matrix or mitigation propositions, and in half of the situations analyzed the relative scoreof EIAs was lower than 30% for the quality of road mortality impact assessment. We recommend the improvement of the terms of reference should be a priority to enforce the elaboration of enhanced quality studies. A Portuguese version of this manuscript is available on request.