Behavior and socioendocrinology of bonobos (Pan paniscus): mechanisms that contribute to the evolution and maintenance of social structure in the other Pan species
MetadataShow full item record
Research into the origins of our own social behavior begins with understanding how environmental elements lead to complex social interaction. Social structure emerges from these interactions as a bottom-up process, whose patterning constitutes the very framework of a society. Studies of behavioral mechanisms are important in determining the full repertoire that results in the social and dominance structures of a species. Hormones such as oxytocin and cortisol facilitate and fluctuate in response to social interactions and measuring their relative values among individuals is a valuable tool in testing functional hypotheses of behavioral mechanisms. The objective of this dissertation is to investigate several fundamental, under-, or previously unstudied behavioral mechanisms and hormonal correlates that shape the unique social system of bonobos. The first study describes the pattern of expression of harassment behavior among immatures and tests predictions generated by the Exploratory Aggression and Rank Improvement hypotheses. Results demonstrate that immatures use harassment to test the nature of existing inter-individual relationships and to explore the parameters of aggressive behaviors and furthers our understanding of juvenile development of aggression and integration into the dominance hierarchy. The second study describes the pattern of occurrence of infant handling and tests predictions generated by several functional hypotheses, including examining the relationship between oxytocin and handling behaviors. Results show a significant sex difference in expression of handling where, during adolescence, male interest in infants sharply declines whereas females continue to handle infants, the expression of which was correlated with oxytocin. These results primarily support the Learning-to-Mother hypothesis and provide insight into the role oxytocin may play in facilitating care-giving behaviors in young females. The final study explores the patterning of female sexual behavior and male aggression, and investigates whether male constraint of female choice imposes a cost to females through induction of a stress response. Results show that while females exercise unconstrained mate choice through proceptive behaviors, males influence female receptivity through aggression and sexual coercion, shedding light on the degree to which rank related asymmetry in male mating success reflects female choice vs. constraint of choice. This dissertation includes previously published and unpublished co-authored material.