Unravelling unique responses of mammal abundance to road proximity in agricultural landscapes

Roads can impact population abundance due to mortality from collisions with vehicles, habitat degradation and loss of connectivity. Some species, however, can be unaffected or even positively affected by roads and roadside environments. Despite this, there is scarce information on population-level responses to roads. To fill this knowledge gap, we sampled medium and large mammals with camera traps near two paved roads with low and high traffic volumes in agricultural landscapes in the Brazilian Cerrado. We used Royle-Nichols' occupancy models to investigate the effects of road proximity on the local abundance of 12 mammal species with varying susceptibility to roadkill. We found that road proximity affected only three species, all of which had high roadkill rates. While two of these species exhibited lower abundance near roads, the third showed the opposite response. For most species, irrespective of their roadkill rates, variations in local abundance were strongly correlated with habitat quality and connectivity. Species' life-history traits, individual behaviour and the impact of roads and traffic on populations over time may explain these idiosyncratic responses.