Multi-Modal Use of a Socially Directed Call in Bonobos

Emilie Genty,Catherine Hobaiter,Klaus Zuberbühler,Zanna Clay,Elsa Addessi

doi:10.1371/journal.pone.0084738

Emilie Genty, Catherine Hobaiter + Show 3 more

Open Access

https://doi.org/10.1371/journal.pone.0084738

Copy DOI

Journal: PloS one	Publication Date: Jan 15, 2014
Citations: 137	License type: CC BY 4.0

Affiliation: University of Neuchâtel, University of St Andrews

Abstract

‘Contest hoots’ are acoustically complex vocalisations produced by adult and subadult male bonobos (Pan paniscus). These calls are often directed at specific individuals and regularly combined with gestures and other body signals. The aim of our study was to describe the multi-modal use of this call type and to clarify its communicative and social function. To this end, we observed two large groups of bonobos, which generated a sample of 585 communicative interactions initiated by 10 different males. We found that contest hooting, with or without other associated signals, was produced to challenge and provoke a social reaction in the targeted individual, usually agonistic chase. Interestingly, ‘contest hoots’ were sometimes also used during friendly play. In both contexts, males were highly selective in whom they targeted by preferentially choosing individuals of equal or higher social rank, suggesting that the calls functioned to assert social status. Multi-modal sequences were not more successful in eliciting reactions than contest hoots given alone, but we found a significant difference in the choice of associated gestures between playful and agonistic contexts. During friendly play, contest hoots were significantly more often combined with soft than rough gestures compared to agonistic challenges, while the calls' acoustic structure remained the same. We conclude that contest hoots indicate the signaller's intention to interact socially with important group members, while the gestures provide additional cues concerning the nature of the desired interaction.

Highlights

A key problem in science is to understand when and how human language evolved and in what aspects it is different from nonhuman animal communication
One way to address these hypotheses is to look for homologous traits and precursors of human linguistic abilities through the comparative study of primate communication. It is unclear whether language evolved from a gestural communication system or whether it has always been based on vocal signals
Contest hoots are call sequences consisting of an introductory phase, an escalation phase composed of several stereotyped units, and a let-down phase (Figure 1)

Summary

Introduction

A key problem in science is to understand when and how human language evolved and in what aspects it is different from nonhuman animal communication. One view is that the language faculty emerged ‘de novo’ over the last few million years of hominid evolution, without any relevant precursors. It is unclear whether language evolved from a gestural communication system or whether it has always been based on vocal signals. A relevant finding here is that humans and great apes make frequent use of gestures, while other primates communicate predominantly with vocalisations and facial expressions. Relevant is that intentional signalling has been mainly found in great ape gestural communication [2] (but see [3] and [4]), while it is less clear whether vocalisations are used intentionally. Primate calls can function to refer to external events, there is usually no strong evidence that they are produced to deliberately inform a recipient about the event witnessed by the caller [5]

Methods

Results

Conclusion