Date of Award

Spring 5-1-2024

Degree Type


Degree Name

Master of Science in Integrative Biology


Department of Ecology, Evolution, and Organismal Biology

Committee Chair/First Advisor

Jared Taglialatela

Second Advisor

Thomas McElroy

Third Advisor

Todd Pierson


The three African great apes, bonobos, chimpanzees and gorillas, despite similar habitats, differ considerably in their sociality and feeding ecology. There have been many studies that have investigated the feeding ecology and social behaviors of these species, but there is extremely limited literature available on how feeding ecology may have affected ape social evolution. Chimpanzees are frugivorous, which forces them into close proximity when foraging given the clumped nature of this resource. Bonobos and gorillas, however, are fallback food consumers, which allow them to spread out as they forage. This thesis project aims to test the hypothesis that differences in feeding ecology has led chimpanzees to be more tolerant of conspecifics in feeding contexts, and gorillas and bonobos to be less so. This study evaluated two main hypotheses: 1) there is a difference in individual social behavior between feeding and non-feeding contexts in all three species, and 2) in feeding contexts, chimpanzees would be the most tolerant of conspecifics, as compared to both bonobos and gorillas. To test these hypotheses, social proximity data were collected from nine chimpanzees (Pan troglodytes), nine bonobos (Pan paniscus), and nine gorillas (Gorilla gorilla) in human care during feeding and non-feeding contexts. Data indicate a significant difference in social proximity scores between feeding and non-feeding contexts in all three species. More specifically, chimpanzees had a significantly higher proximity score during feeding contexts than either bonobos or gorillas. These results suggest that feeding ecology has likely affected the social evolution of these species. Future studies in both wild and human care settings are needed to further test this hypothesis.

Available for download on Friday, May 09, 2025