Function and distribution of coalitions in captive bonobos (Pan paniscus)

We examined the distribution of support behaviour within a captive group of bonobos. Most support was evoked by inter-sexual conflicts with the two hi ghest ranking females. Within a dyad, the usual winner was most often suppo rted. Individuals that challenged the rank order by aggressions and pesteri ng were aggressed more often by their targets in the company of an ally. Th e two lowest ranking males served as scapegoats, receiving 80% of the contr a-support. In coalitions, individuals did not aggress victims they would no t dare to attack without supporters. However, the victims of coalitions rea cted more strongly with fear and rarely counteraggressed than when being at tacked alone, indicative of the high impact of aggression in support. The a lpha female showed some control behaviour when intervening in conflicts. Th e data fitted with several functional hypotheses: coalitions functioned to maintain existing ranks, to acquire ranks, to reduce tension, and to test o r strengthen the bond. We suggest that support behaviour fulfilled a crucia l role in the maintenance of the power of the two highest ranking females o ver the males. Among the females themselves the dominance relationships wer e not based on coalitions, but on individual attributes.