Vocal “duel” between groups of howler monkeys: better have the final say!

This study examined 46 encounters between groups of black howler monkeys (Alouatta pigra) in Palenque, Mexico, to understand how their vocalizations affect contest outcomes. Groups were more likely to prevail when adult males ended bouts in coordination, when females joined in, when sequences were longer, and when they began with roars call type. In contrast, who initiated the howling bout, the number of adults present had no effect. The results show that these “vocal duels” are structured displays signaling group cohesion and motivation.