Social network analysis shows direct evidence for social transmission of tool use in wild chimpanzees.

Catherine Hobaiter,William Hoppitt,Timothée Poisot,Thibaud Gruber,Klaus Zuberbühler,Frans B M De Waal

doi:10.1371/journal.pbio.1001960

Abstract

Author SummaryChimpanzees are widely considered as the most “cultural” of all animals, despite the lack of direct evidence for the spread of novel behaviors through social learning in the wild. Here, we present a novel, dynamic network-based diffusion analysis to describe the acquisition patterns of novel tool-use behavior in the Sonso chimpanzee community of Budongo Forest, Uganda. We find strong evidence for social transmission of “moss-sponging” (the production of a sponge consisting of moss) along the innovators' social network, demonstrating that wild chimpanzees learn novel tool-use behaviors from each other and supporting the more general claim that some of the observed behavioral diversity in wild chimpanzees should be interpreted as “cultural.” Our model also estimated that, for each new observation, naïve individuals enhanced their chances of developing moss-sponging by a factor of 15. We conclude that group-specific behavioral variants can be socially learned in wild chimpanzees, addressing an important critique of the claim of culture in our closest relatives.

Highlights

Progress in network analysis has made it possible to test whether the spread of novel behaviors in animal groups has occurred through individual learning or social transmission [1,2,3,4,5]
We find strong evidence for social transmission of ‘‘moss-sponging’’ along the innovators’ social network, demonstrating that wild chimpanzees learn novel tool-use behaviors from each other and supporting the more general claim that some of the observed behavioral diversity in wild chimpanzees should be interpreted as ‘‘cultural.’’ Our model estimated that, for each new observation, naıve individuals enhanced their chances of developing moss-sponging by a factor of 15
Time, rather than employing patterns of association as a proxy for demonstrations. We applied this method to two novel tool-use behaviors that appeared in the Sonso chimpanzee community of the Budongo Forest, Uganda (Pan troglodytes schweinfurthii)

Summary

Introduction

Progress in network analysis has made it possible to test whether the spread of novel behaviors in animal groups has occurred through individual learning or social transmission [1,2,3,4,5]. This method has been successfully applied in several species, including primates [3,6,7]. Dynamic networks change to reflect the time course of the observations and are more powerful than static networks, by tracing which individuals are likely to have observed the novel behavior across time

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Results

Discussion

Conclusion