Targeted helping and cooperation in zoo-living chimpanzees and bonobos.

Suska Nolte,Josep Call

doi:10.1098/rsos.201688

Abstract

Directly comparing the prosocial behaviour of our two closest living relatives, bonobos and chimpanzees, is essential to deepening our understanding of the evolution of human prosociality. We examined whether helpers of six dyads of chimpanzees and bonobos transferred tools to a conspecific. In the experiment ‘Helping’, transferring a tool did not benefit the helper, while in the 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 the experiment ‘Helping’. By 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 species difference in whether receivers reached to obtain tools. Thus, receivers' behaviour did not explain the lack of transfers from chimpanzee helpers. This study supports the notion that bonobos might have a greater ability to understand social problems and the collaborative nature of such tasks.

Highlights

Many animal species live in complex social groups, where individuals compete over resources and show a variety of seemingly complex cooperative behaviours
Four of the six tested bonobo dyads contributed to the number of observed transfers and in each dyad, we found a similar pattern of mainly sharing in the two test conditions
While we found multiple spontaneous tool transfers in all female–female bonobo dyads even when they did not directly benefit from it, only two transfers occurred in a mother–daughter chimpanzee dyad and none in the other chimpanzee dyads

Summary

Introduction

Many animal species live in complex social groups, where individuals compete over resources and show a variety of seemingly complex cooperative behaviours. The term cooperation has been defined as actions that are beneficial to both the actor and the recipient [1]. In order for a cooperative act to occur, both individuals need to invest into reaching a mutual goal and both gain a benefit from it. We find cooperative behaviours in various distantly related species such as ants [2], cleaner fish [3], ravens [4], wolves [5] and royalsocietypublishing.org/journal/rsos R.

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Conclusion