From kin to spatial proximity conspecifics: social network reorganisation in developing juvenile vervet monkeys

Navigating social relationships is a primary determinant of fitness in group-living animals and thus the transition of individuals from infancy to fully fledged group members is marked by concomitant changes in interactions. This developmental trajectory is particularly relevant in primates, where individuals must navigate a social landscape composed of different types of relationships and interactions while gaining independence from their mothers. Yet, little is currently known about how different layers of sociality, like proximity and grooming interactions, co-develop during the sensitive juvenile phase. Here, we harness multilayer network analysis on observations from 18 wild vervet juveniles (4-36 months of age) from two social groups to dissect the maturation of the juvenile social network. We quantify developmental trajectories across three complementary scales: maternal dyadic interactions, individual network centrality, and global network topology. We find that social maturation is defined not by simple network expansion, but by structural reorganisation. Specifically, juveniles shed their early bias toward mothers and kin, replacing these primary bonds by social interactions aligning with spatial proximity. This restructuring is further modulated by socio-demographic traits. Higher maternal rank confers access to influential partners, while females are more central than males in grooming networks, foreshadowing adult social roles. By charting the reorganisation of multiple social layers, this study unravels the processes underpinning the juvenile transition to independence in primates.