Behaviour 2019
Reciprocity and behavioral heterogeneity govern the stability of social networks
Roslyn Dakin1,2, Brandt Ryder1,3. 1Smithsonian Institution, Washington, DC, United States; 2Carleton University, Ottawa, Ontario, Canada; 3Bird Conservancy of the Rockies, Fort Collins, Colorado, United States

In human and animal societies, social relationships form a dynamic social network that can change with time. Why are some social network structures more stable than others? We addressed this question by studying a bird species, the wire-tailed manakin, where male social behavior is associated with fitness. Our analysis demonstrates that denser social networks are inherently less stable, and we show that this pattern is due to a trade-off between the number of partnerships an individual has and his ability to maintain stable relationships through time. This trade-off can be explained by a simulation model that combines two simple behavioral processes: reciprocity (defined as a preference for previous partners) and individual heterogeneity (defined as repeatable among-individual differences in social behavior). These mechanisms may govern the stability of social networks in diverse cooperative and competitive systems.