Effects of Rainfall Variability on Habitat Preferences and Population Dynamics of Neotropical Primates in the Peruvian Amazon

Abstract

The Neotropics is characterized by high primate species richness, particularly in western Amazonian assemblages. Habitat preferences and population dynamics of Neotropical primates have been studied from several different angles including: population synchrony, resource availability, forest structural variation, and rainfall variation. Seasonal variation between rainy and dry seasons is further complicated by larger scale El Niño and La Niña events thought to be influenced by climate change. This study seeks to build on hypotheses and findings of previous studies by asking: What is the relationship between extreme rainfall variation in the Amazon and population dynamics of frugivorous, insectivorous, folivorous, and seed-eating primates? Studies have shown a strong correlation between fruit availability and frugivorous primate abundance, but there is still uncertainty regarding drivers of changes in population structures of non-frugivores. This study examines the habitat preferences and population dynamics of seven Peruvian primate species in relation to annual rainfall variation and El Niño southern oscillation (ENSO) events. I conducted line-transect census surveys in the Pacaya Samiria National Reserve, Peru during the dry season of 2017. Using long-term data from 2006-2017, I analyzed the extent to which primate habitat preference, density, and abundance are correlated with annual rainfall and El Niño events. There were no significant habitat preferences for any species in 2017, but the common squirrel monkey (Saimiri boliviensis) and all species when considered collectively showed significant habitat preferences for 2006-2017. All species showed vertical height stratification, meaning they effectively occupy different ecological spaces on the vertical gradient. The red howler monkey (Alouatta seniculus) and common woolly monkey (Lagothrix lagotricha) exhibited a three-year lagged effect of population abundance in response to rainfall variation. In addition to investigating rainfall variation, future research should explore the relative influence of interspecific interaction, ecological overlap, phenology, resource availability, and disease on primate population dynamics.