The Behavioural Ecology of a Potentially Undescribed Morph of Saki Monkey (genus Pithecia) in a Highly Diverse Primate Community

Sammanfattning: The importance of tropical forests for global diversity and ecosystem function is well established in scientific literature, but is undermined by gaps in our knowledge of tropical ecosystems and species. Primates play important functional roles in these ecosystems, and despite constituting one of the most well-recognised taxa in the world, many species remain poorly studied. The Area de Conservación Regional Communal Tamshiyacu-Tahuayo (ACRCTT), located in the northeastern Peruvian Amazon, harbours one of the most diverse primate assemblages in the world and presents an ideal opportunity for the study of primate communities and mechanisms of their coexistence. Previous research has recorded the presence of an atypically coloured morph of monk saki monkeys (Pithecia monachus, sensu Marsh 2014) living in sympatry with a population of burnished sakis (Pithecia inusta, sensu Marsh 2014) in the reserve. In this study, the behavioural ecology of this potentially undescribed morph of saki monkey is described, using continuous focal data collected during the early wet season in the ACRCTT. The sakis were most often encountered in multi-adult groups and in the upper forest strata. The observed feeding strategies suggest that fruits and/or seeds constitute the sakis' primary food source in the wet season, although arthropods were also ingested during a large proportion of feeding records. Sex differences in behavioural patterns provide support for a difference in male and female investment in group defence. As only the monk saki morph was encountered during the study, the potential for seasonal habitat differentiation between the saki populations at the ACRCTT is discussed. A survey of primates in flooded and non-flooded forest areas at the ACRCTT was also conducted, in which nine of the 14 primate species recorded at the ACRCTT were encountered. Significant differences in the vertical distribution of primate groups provide evidence for vertical stratification in the ACRCTT primate community. This study contributes to previous research on the poorly-studied Pithecia genus, and provides insights into the mechanisms of niche differentiation between Pithecia and other primates.