Elsevier

Animal Behaviour

Volume 123, January 2017, Pages 305-316
Animal Behaviour

Production of and responses to unimodal and multimodal signals in wild chimpanzees, Pan troglodytes schweinfurthii

https://doi.org/10.1016/j.anbehav.2016.10.024Get rights and content

Highlights

  • Repertoire of 48 ‘free’ multimodal (MM) signals documented in wild chimpanzees.

  • MM signals were produced at significantly lower rates than unimodal (UM) signals.

  • Chimpanzees show flexible usage of UM and MM signals across behavioural contexts.

  • Response more likely to MM grunt-gesture than grunt alone, but not gesture alone.

Animals communicate using a vast array of different signals in different modalities. For chimpanzees, vocalizations, gestures and facial expressions are all important forms of communication, yet these signals have rarely been studied together holistically. The current study aimed to provide the first comprehensive repertoire of flexibly combined (‘free’) multimodal (MM) signals, and assess individual and contextual factors influencing production of, and responses to, unimodal (UM) and MM signals in wild chimpanzees. In total, 48 different free MM signals were produced. MM signals were produced at a significantly lower rate than UM signals, but 22 of 26 focal animals were observed to produce free MM signals. The relative production rates of different types of UM and MM signals differed significantly between the behavioural contexts investigated, showing flexible use of signals across contexts. In contrast, individual factors such as age, sex or rank of signaller did not appear to influence the type of signal produced or the likelihood of eliciting a response. Finally, we compared recipient responses to free MM grunt-gesture signals and matched UM component signals and found that these MM signals were more likely to elicit a response than a grunt alone, but were as likely to elicit a response as the gesture alone. The overall findings point to a widespread capacity for wild chimpanzees to flexibly combine signals from different modalities and highlight the importance of adopting a multimodal approach to studying communication.

Section snippets

Study Site and Subjects

This study was carried out in Kibale National Park, located in western Uganda (0″13′–0″41′N and 30″19′–30″32′E) in 2013–2015. A detailed description of the characteristics of the forest can be found in Chapman and Wrangham (1993). The study animals were a wild group of chimpanzees, the Kanyawara community. In 2013, the group comprised approximately 57 individuals (Muller & Wrangham, 2014), and occupied a home range of around 16.4 km2 (Wilson, Kahlenberg, Wells, & Wrangham, 2012). The community

MM Signals: Repertoire, Rates and Responses

Overall, the results show that across rest, feed and groom contexts MM signals were rare relative to UM signals (see Fig. 1). Free MM signals were, however, produced by 22 of the 26 focal individuals, and we recorded a total of 48 different free MM signals, consisting of combinations that in total included six different facial expressions, nine different vocalizations and 16 different gestures (see detailed MM repertoire in Supplementary Table S3). Vocal-gestural combinations were the most

Discussion

Although MM signals may not be as common as UM signals, this study has documented the production of 48 different free MM combinations. While 22 of 26 individuals produced at least one free MM signal, each broad type of MM signal combination was observed to be produced by at least nine of the 26 focal individuals. This suggests that the vast majority of individuals have the capacity and motivation to flexibly and simultaneously combine signals from different modalities, albeit rarely. In the

Acknowledgments

We are grateful to the directors of Kibale Chimpanzee Project for permitting and supporting us to carry out this research on the Kanyawara community of chimpanzees. We are also thankful to the KCP field manager Emily Otali and the KCP field assistants, Dan Akaruhanga, Seezi Atwijuze, Sunday John, Richard Karamagi, James Kyomuhendo, Francis Mugurusi, Solomon Musana and Wilberforce Tweheyo, for their valuable assistance and support in the field. We thank Simon Townsend for statistical advice, and

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