Abstract: Animals’ social relationships/bonds are influenced by both ecological factors and the structure of the social organization they live in. Current socioecology models are very good at explaining consistent between-species and between-population variation related to both factors, but there is considerable within-species and with-population variation that is poorly understood. Mountain gorillas (Gorilla beringei) are an unusual species because they are regularly observed in many different types of social groups (e.g. one male, multi-female ‘harems;’ multi-male, multi-female groups; all-male groups), which makes them an important biological system for understanding sources of within-species or population variation. The value of social bonds between certain types of partners (e.g. adult males and infants, adult females and adult males) may vary systematically with social group structure. In this talk, I will present data on the relationship between social group structure and individual social bond strength of wild mountain gorillas. The structure of the social group predicts variation in bond strength between males and infants, and males and females, though not between mothers and infants. Eigenvector centrality analyses suggest the presence of multiple males has important consequences for relationships between adult males and females, and that the ratio of males to either females or infants in the group matters more than the absolute number of males for predicting social bond strength. I will also discuss ongoing work on the relationship between gorillas’ social networks, social bonds, and the steroid hormones cortisol and testosterone. Results like these help behavioral ecologists refine our understanding of observed behavioral plasticity, and may have important implications for long-term management of this critically endangered species.
Bio: Stacy Rosenbaum is a biological anthropologist at the University of Chicago’s Institute for Mind and Biology and the Lincoln Park Zoo’s Davee Center for Epidemiology and Endocrinology. After completing her PhD at UCLA in 2014, she was awarded a National Science Foundation Postdoctoral Fellowship for her research on the evolution of social behavior and its physiological underpinnings. Her work explores the function and impact of social bonds in wild mountain gorillas living in Volcanoes National Park, Rwanda.