Consistent individual variation across interaction networks indicates social personalities in lemurs

Group members interact with each other during multiple social behaviours that range from aggressive to affiliative interactions. It is not known, however, whether an individual's suite of social behaviours consistently covaries through time and across different types of social interactions. Consistent social behaviour would be advantageous in groups, especially when individuals need to remember their group members' social roles and preferences in order to keep track of social relationships and predict conspecifics' future behaviour. Here, we address whether social behaviour of ringtailed lemurs, Lemur catta, is consistent through time and across four interaction networks (aggression, grooming, contact calling, scent marking). We quantified variation in social behaviour through four network centrality measures including outdegree, outstrength, betweenness and eigenvector centrality. Comparing lemurs' measures across 2 years revealed that network centrality remained consistent between years. Lemurs' centrality also stayed consistent across interaction networks: individuals with high centrality in one interaction network also had high centrality in the other networks, even when we controlled for sex-based variation in social behaviour. Thus, regardless of their sex, some individuals were highly social and frequently groomed others, initiated aggressive interactions and responded to others' contact calls and scent marks. Lemurs also had preferred social partners they frequently interacted with across years and across multiple behaviours. In particular, lemurs frequently responded to the contact calls and the scent marks of the conspecifics they had frequently groomed. Together, these results demonstrate that individual variation in lemur social behaviour is not context specific, but instead persists through time and across multiple social interactions. Such consistent behaviour provides evidence of social personalities, which may influence individuals' interaction styles, including how socially active they are and with whom they interact.