Habitat heterogeneity as a local and regional-scale driver of primate assemblage structure in northernmost Brazilian Amazonia

Abstract

We performed line transect surveys in two fishbone human settlements (defined as clearings cut through forests in a fishbone pattern, extending along secondary roads from a main road) in different vegetation types, as well as in one protected area. A total of 410 sightings of eight primate species were recorded in the three study areas. The mean total primate abundance was 3.28 groups/10 km walked, and there were significant differences between areas with different plant physiognomies. The abundance of the larger primate species Alouatta macconnelli and Ateles paniscus (Atelidae) was higher in the dense ombrophilous forests of the Entre Rios human settlement, whereas those of all the other species were higher in the forest mosaics of the Novo Paraíso human settlement and Viruá National Park. The habitat generalist Sapajus apella presented the highest abundances in all the areas. No significant differences were detected in relative biomass between study areas. Additionally, no significant differences were detected in the overall abundances or relative biomasses of the hunted species (Sapajus apella, Alouatta macconnelli, Ateles paniscus, and Chiropotes chiropotes) between study areas. Human impact has been recognized as shaping primate assemblages. However, in this study, primates were not part of the dietary repertoire of the non-Amazonian immigrants inhabiting the fishbone human settlements. Thus, although the primate assemblages varied considerably at the regional and local level, they were shaped by habitat heterogeneity, which allowed the competing species to coexist through habitat segregation.