Chimpanzees cooperate in a competitive world Open Access

Suchak, Malini Christine (2013)

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Experimental cooperation studies on primates often remove several important challenges to successful joint action. By testing the primates in pairs, partner choice is eliminated and competition and freeloading are sharply reduced. Wild primates, including chimpanzees (Pan troglodytes), are able to handle these challenges, whereas the mixed outcome of pairwise testing may have been due to limited ecological validity. The purpose of this study was to examine cooperative behavior in an open group setting by testing how captive chimpanzees coordinate with multiple partners of their own choosing. All members of the group (n=11) had access to the cooperation apparatus in a large outdoor compound. Chimpanzees were tested under two conditions: (1) dyadic cooperation, requiring two individuals and (2) triadic cooperation, requiring three individuals, to pull in a tray baited with food. The chimpanzees learned to solve the task in both conditions and were extremely successful, performing 3,565 cooperative pulls (in 94 one-hour sessions). Efficiency increased over time and the chimpanzees began to pull more when a partner was present, demonstrating that the chimpanzees gained an understanding of the task in both conditions. Chimpanzees preferentially approached the apparatus when individuals of similar rank or kin were present and were more successful when working with kin versus non-kin. Cheating was not particularly widespread with 98.90% of rewards being obtained by the individual who worked for them. A number of responses seemed to discourage freeloading: withdrawing to prevent further opportunities for freeloading, withholding pulling until the cheater left, and in rare cases agonism. This experiment demonstrates that in the midst of a complex social environment, subject to competition and intolerance, chimpanzees can initiate and maintain a high degree of cooperative behavior.

Table of Contents

Chapter 1. Introduction 1

Defining Cooperation


Observational evidence for cooperation in nonhuman primates


Experimental evidence for nonhuman primate cooperation


Outline of the current paper

15 Chapter 2.

Chimpanzees successfully cooperate in duos and trios despite potential competition: Partner choice

16 Abstract 17 Introduction 18 Methods

Subjects and housing

21 Apparatus 23 Procedures 24

Behavioral coding

25 Analyses 26 Results

Acquisition of the task

29 Partner choice 34

Description of recruitment events


Constraints on partner choice

41 Discussion 44 Chapter 3.

Why freeloading does not pay in chimpanzees

48 Abstract 49 Introduction 50 Methods

Subjects and housing

54 Apparatus 55 Procedures 56

Behavioral coding

56 Analyses 58 Results

Prevalence of cheating


Responses to cheating

61 Discussion 63 Chapter 4.

General discussion, synthesis and future directions

67 References 74

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