Thesis: The influence of seasonal food availability on diet, foraging and grouping patterns of eastern chimpanzees in Nyungwe National Park, Rwanda
Resource availability undoubtedly contributes to the wide array of inter- and intraspecific social organisation evident in primates. According to socioecological theory, differences arise because of resource competition particularly affecting females who bear reproductively high energetic costs. In support of this, primates often form larger groups when resource availability is high and thus competition low, however there are numerous confounding ecological and social pressures that may also influence grouping patterns. Fission-fusion grouping dynamics are exhibited by a range of taxa including elephants, hyenas, dolphins, bats and primates such as chimpanzees and hunter-gatherer humans. It allows individuals to form foraging parties that fluctuate in size, composition and duration in response to external pressures. This flexibility in grouping patterns is especially beneficial for populations living in seasonal environments characterised by low resource diversity and productivity such as montane (high elevation) forests. Animals may cope with seasonal decreases in food availability by altering their diet, foraging, ranging and social behavior. In differing habitats chimpanzees display high levels of behavioural diversity, however populations subsisting in resource deficient forested habitats have received little attention in comparison to their lowland counterparts.
My PhD aims to assess the ultimate influence of temporal and seasonal food availability on diet, foraging and grouping patterns of eastern chimpanzees living in Nyungwe National Park, Rwanda. Montane forests are extremely marginal in Africa and Nyungwe forms part of the Albertine Rift which encompasses one of the largest blocks of contiguous montane forest on the African continent. The Albertine Rift is also the sole location that eastern chimpanzees exploit montane forests, rendering it a highly unique and important habitat type to assess chimpanzee intraspecific diversity. I expect that in an environment already low in primary productivity that the added effect of seasonality will place strong constraints on sociality. Additionally, I am interested in exploring the proximate mechanisms by which chimpanzees achieve their desired grouping patterns by examining the role of long-distance pant-hoot calls in facilitating fission and particularly fusion events.
I will be conducting my field work in Nyungwe from June 2016 – September 2017 in collaboration with the Kitabi College of Conservation and Environmental Management and the University of Rwanda through my external supervisor Prof. Beth Kaplin.
Why my research is important
This study will enhance understanding of chimpanzee socioecology and the constraints faced by primates in montane forests with unique selective pressures. It also has important implications for understanding evolutionary processes and human evolution since fallback food (foods consumed at a higher rate when preferred foods are unavailable) use has been hypothesised as playing an integral role in selecting anatomical and behavioural traits that may have driven advancement towards hominins. Data gathered may also be used to assist with early hominid behavioural reconstructions since broad interdisciplinary comparisons can shed light on general ecological principals that influence hominid socioecology.
Importantly the project has conservation implications for this endangered species as a thorough understanding of the resource and habitat requirements of a population is essential to its correct management and protection practices. It will also facilitate the continuation of chimpanzee-focused ecotourism which generates revenue for the national park and increases public support for ape conservation on a national and international level.