Responses of ground-dwelling birds and mammals to local environmental variables and human pressure in an Amazonian protected area

Vertebrates play key roles as seed dispersers, herbivores, and top predators in tropical ecosystems. Therefore, obtaining population estimates for these species and understanding the factors that affect them are essential for wildlife management since changes in their populations have consequences for entire ecosystems. Vertebrate abundances in tropical forest may be related to habitat characteristics, resource seasonality, and human pressure. However, how ecological variables and human pressure concurrently influence animal abundances is not well understood. We investigated the associations between the number of records of vertebrates (ground-dwelling birds and medium- and large-sized mammals) and habitat features, food availability, and human pressure in a sustainable protected area in the Brazilian Amazon of western Pará, Brazil. Our study design included the recording of animals at 38 camera trap stations, sampling of environmental variables (canopy cover, leaf area index, tree height, and local altitude) and food resources (fruit or prey biomass), and measurement of a hunting pressure proxy (distance from human settlements). Our results indicated that groups responded in different ways: omnivorous mammals were affected positively by local altitude, canopy openness, and leaf area index; game birds were affected positively by local altitude and leaf area index; ungulates were affected negatively by local altitude and positively by food resources; and large rodents were affected only by food resources (positively). In contrast, insectivorous mammals and mesopredators were not affected by any variable we tested. Surprisingly, no groups responded to distance from human access, although the low number of records of large species, such Tapirus terrestris and Dicotyles tajacu, suggests that the sampled area may suffer from significant hunting pressure.