Male social bonds and rank predict supporter selection in cooperative aggression in wild Barbary macaques

Highlights• Wild male Barbary macaques formed stable, strong, differentiated social bonds.• Strong bonds endured even through intensely competitive mating seasons.• Rank and bond strength predicted which bystander males were recruited to coalitions.• Males rejected recruitment from weakly bonded and low-ranked recruiters.• Supporter selection is based on two independent criteria.