Coping with conflict during initial encounters in chimpanzees

When strangers meet, conflict is likely to arise from incompatibilities in motivations and expectations, as well as from the absence of predictability in interactions, This study explores the mechanisms that mitigate aggression, permit mutual evaluation, establish tolerance, and facilitate the development of social bonds between unfamiliar chimpanzees (Pan troglodytes). Data collected during the initial half-hour of the introduction of 33 unfamiliar pairs (16 female-male and 17 female-female) at the Yerkes Primate Center and Detroit Zoo were used to assess the sequence of events during initial encounters and the function of different behaviour patterns in the formation of relationships. Initial encounters followed a regular sequence of interactions (i.e. a 'species-typical etiquette'), commencing with agonistic behaviour, followed by brief friendly touches, and finally allogrooming. Brief friendly touches, which are associated with conciliatory and tension-reducing functions in established relationships, appeared to serve an evaluative function related to status differentiation during initial interactions. In fact, individuals more closely matched in competitive ability (inferred from their eventual dominance rank distance) exchanged friendly touches at higher rates than those more obviously mismatched. These evaluative touches may represent a safer alternative to more assertive interactions when assessments of competitive ability are required in situations likely to escalate. Allogrooming promoted the development of tolerance and relaxed proximity; it was, in fact, effective in reducing agonism and negative-outcome approaches. Allogrooming may take on a particularly important role in reducing agonism because it begins the commerce of benefits that balance the dispersive competitive forces and enable cohesive social groupings.