Taylor Rystrom, S. Helene Richter, Norbert Sachser, Sylvia Kaiser

Individualized social niches arise in social groups and are associated with behavior and hormone (e.g. cortisol) concentrations. During sensitive life phases, social interactions can have a profound impact on the development of social behavior. Focusing on adolescence, we aimed to investigate the relationship between the social niche, social behavior, and cortisol concentrations (baseline and response to challenge) in female guinea pigs. Females were pair-housed in early adolescence (initial social pair formation), and a social niche transition occurred after six weeks by replacing the partner with either a larger or smaller female, forcing the focal female to become dominant or subdominant. We show that social behavior and cortisol concentrations were influenced by dominance status. Dominant females were more aggressive in the initial social pairs, and this was immediately reshaped after the social niche transition. Submissive behavior toward the new social partner was also rapidly adjusted after the social niche transition. However, submissive behavior was not entirely reshaped because the previous dominance status from the initial social pair still affected the extent of submissive behavior three weeks after the social niche transition. Regarding cortisol concentrations, baseline levels were shaped by the social niche in early adolescence with higher concentrations measured in dominant females. After the social niche transition, cortisol responsiveness significantly increased for the females who were forced to become subdominant relative to those forced to become dominant. These results add substantially to our understanding of the effect of social interactions during adolescence on social behavior and hormone concentrations in females.