Targeted Helping and Cooperation in Zoo-living Chimpanzees and Bonobos

Directly comparing the behaviour of our two closest living relatives, chimpanzees and bonobos, during prosocial tasks is essential to deepen our understanding about the evolution of human prosociality. We examined whether helpers of six dyads of chimpanzees and bonobos transferred tools to a conspecific. In experiment ‘Helping’, transferring a tool did not benefit the helper while in experiment ‘Cooperation’ the helper only obtained a reward by transferring the correct tool. Chimpanzees did not share tools with conspecifics in either experiment, except for a mother-daughter pair, where the mother shared a tool twice in experiment ‘Helping’. In contrast, all female-female bonobo dyads sometimes transferred a tool even without benefit. When helpers received an incentive, we found consistent transfers in all female-female bonobo dyads but none in male-female dyads. Even though reaching by the bonobo receivers increased the likelihood that a transfer occurred, we found no significant specie...