Interspecific primate associations in Amazonian flooded and unflooded forests

Stable associations between two or more primate species are a prominent feature of neotropical forest vertebrate communities and many studies have addressed their prevalence, and their costs and benefits. However, little is known about the influence of different habitat types on the frequency, seasonality, and composition of mixed-species groups in Amazonian forest primates. Here we examine the features of interspecific primate groups in a large mosaic of flooded (varzea and igap) and unflooded (terra firme) forest in central Amazonia. In total, 12 primate species occurred in the study area, nine of which were observed in mixed-species associations. Primates were more than twice as likely to form associations in varzea forest than in terra firme forest. Squirrel monkeys were most frequently found in mixed-species groups in all forest types, most commonly in association with brown capuchins. Another frequent member of interspecific associations was the buffy saki, which often formed mixed-species groups with tamarins or brown capuchins. There was no seasonality in the frequency of associations in terra firme forest whereas associations in varzea forest were twice as frequent during the late-dry and early-wet seasons than in the late-wet and early-dry seasons. Interspecific primate associations were common in all forest types, but the degrees to which different species associate varied between these environments. We suggest that the temporal variation of varzea forest associations is connected with seasonal changes in habitat structure and resource abundance. However, more work is needed to pinpoint the underlying causes of mixed-species associations in all forest types and their strong seasonality in varzea forest.