LAUSR

The Amazon is recognised as one of the most conserved tropical rainforests in the world. However, along its peripheral agricultural frontiers, mammal assemblages are gradually being eroded due to deforestation of this large area known as the Arc of Deforestation, particularly along the Amazon's southeast. In this study, we aimed to expand on the knowledge of richness, composition, and defaunation of mammal assemblages in two priority protected areas for biodiversity in the region: Cristalino State Park (hereafter Cristalino) and Xingu State Park (hereafter Xingu). We used camera traps and line transects for data collection between 2020 and 2021. Our results demonstrated that both protected areas support rich assemblages of medium‐ and large‐sized mammals within the south‐central Amazon (Cristalino—32 species, Xingu—30 species). Due to the differing vegetation types between each park, the two mammal assemblages showed significant differences in species composition. Even with one of the highest biomasses of large ungulates (tapir and brocket deer) and apex predators (jaguar and puma) compared to other protected areas in south‐central Amazon, both areas showed a high biomass defaunation index relative to these same areas. The result is largely driven by the low abundance of peccaries, especially Tayassu pecari. This could be one of the impacts of extensive human pressure caused by deforestation and degradation around and inside these protected areas. Both parks play an important role in the survival of threatened mammals, and in maintaining biodiversity and ecosystem functionality in the southern Amazon, helping to curb agricultural expansion into the interior of the Amazon rainforest.