Individual differences drive social hierarchies in mouse societies

Social hierarchies structure groups and confer competitive advantages on high-ranking individuals. In mice, social hierarchies are expressed through proactive and competitive behaviors. Yet it remains unclear how these behavioral domains interact to shape social position in naturalistic groups, and whether hierarchical position reflects a stable individual trait that persists across different social contexts, or emerges from current group composition. To address these questions, we developed the NoSeMaze, a semi-naturalistic, open-source, modular platform that enables automated long-term tracking of unperturbed mouse groups. Across more than 4,000 mouse-days, hierarchies derived from naturalistic tube competitions were non-despotic, transitive, and stable even when group compositions changed. Thus, social rank reflected an internalized trait that individuals carried across different social contexts. Proactive chasing also showed trait-like stability, but was concentrated among high-ranking individuals, reflecting reciprocal status negotiation and contestation within the social elite. The link between chasing and rank strengthened in groups with less well-defined hierarchies, where mice relied more on aggressive signaling to assert their position. Consistent with multidimensional mouse personalities, chasing and social rank were only punctually associated with simultaneously measured physical and cognitive traits. In summary, naturalistic high-dimensional tracking with the NoSeMaze reveals the multifaceted organization of social hierarchy in mice, with stable, personality-like traits as a major axis. The approach thus enables modeling individuality and social status as key resilience factors within naturalistic mouse groups.