Leaders are somethin' else: behavioural variation associated with roles during tandem running recruitment

Leadership in social groups often emerges from consistent interindividual differences in behaviour, yet how personality shapes role specialisation remains poorly understood. We investigated how personality traits (exploration, activity, aggression and boldness) influence leadership roles in the ant Pachycondyla striata during tandem running, a recruitment strategy where a leader ant guides a single follower to a target destination. Using repeated behavioural assays (open-field, novel object, aggression tests) and forced emigrations, we assessed individual consistency in personality traits and recruitment roles (leader or follower). We found moderate-to-strong repeatability in activity, exploration, and aggression, as well as strong repeatability in leadership/following roles during tandem recruitment. Behavioural responses changed over time: activity decreased and aggression increased after the first trial, suggesting familiarisation with testing contexts or diminishing novelty effects after initial exposures. Tandem runs declined sharply in subsequent emigrations as ants transitioned to solitary navigation—a faster strategy once routes were learned. This highlights how experience alters collective decision-making, favouring speed over recruitment. More importantly, active and exploratory ants were significantly more likely to become leaders, suggesting intrinsic behavioural differences drive task specialisation. By linking personality to role specialisation, this study advances in revealing how individual consistency shapes collective outcomes in social groups. Understanding these mechanisms could provide broader insights into leadership emergence across animal societies.