Communication and cooperation in wild chimpanzees (Pan troglodytes schweinfurthii)

• Main Author: Wilke, Claudia
• Other Authors: Katie, Slocombe
• Published: University of York 2016
• Subjects: 599.885159
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.714367

Comparisons between animal and human communication are invaluable for understanding the evolution of language and, as our closest living relatives, chimpanzees can provide particularly important insights into this. Here I examined unimodal (UM) and multimodal (MM) communication in wild chimpanzees, in an integrated manner. I found that although MM signals were produced infrequently, and at lower rates compared to captivity, the vast majority of adult and sub-adult individuals did freely combine vocal, gestural and facial signals to produce MM signals. A total of 48 free MM signal combinations were observed, incorporating a wide range of different signal types from different modalities. Focusing on one specific vocalgestural MM signal, I found that MM combinations and UM gestural signals were more successful in eliciting responses compared to UM vocal signals. To investigate signal function more systematically I focused on one common grooming gesture, the big loud scratch (BLS), and tested several competing functional hypotheses. I found little evidence to support the hypotheses that this signal operates as an attention-getter, or as a referential signal. In contrast, my data suggested that in this community of chimpanzees, the BLS facilitates the negotiation of roles within a grooming bout. Groomers used BLSs to request grooming during grooming bouts and the BLS seemed to show willingness to groom, both to initiate a grooming bout, and potentially during a bout when groomees intend to start grooming their partner. Finally, to explore the theoretical link between the evolution of communication and cooperation I tested whether, on an individual level, there was a positive relationship between communicativeness and cooperativeness in chimpanzees. In contrast to theoretical predictions, I found a significantly negative relationship between these two domains, indicating that more communicative chimpanzees were less cooperative. I explore several potential explanations for this highly unexpected finding.