International Journal of Comparative Psychology

Play fighting in many species involves partners competing to bite one another while avoiding being bitten. Species can differ in the body targets that are bitten and the tactics used to attack and defend those targets. However, even closely related species that attack and defend the same body target using the same tactics can differ markedly in how much the competitiveness of such interactions is mitigated by cooperation. A degree of cooperation is necessary to ensure that some turn-taking between the roles of attacker and defender occurs, as this is critical in preventing play fighting from escalating into serious fighting. In the present study, the dyadic play fighting of captive troops of 4 closely related species of Old World monkeys, 2 each from 2 genera of Papio and Mandrillus, was analyzed. All 4 species have a comparable social organization, are large bodied with considerable sexual dimorphism, and are mostly terrestrial. In all species, the target of biting is the same – the area encompassing the upper arm, shoulder, and side of the neck – and they have the same tactics of attack and defense. However, the Papio species exhibit more cooperation in their play than do the Mandrillus species, with the former using tactics that make biting easier to attain and that facilitate close bodily contact. It is possible that species differences in how rigidly dominance relationships are maintained are expressed in the play of juveniles by altering the balance between competition and cooperation.