Towards a great ape dictionary : inexperienced humans understand common nonhuman ape gestures

Funding: This research received funding from the European Union’s 8th Framework 287 Programme, Horizon 2020, under grant agreement no 802719 to CH (https://ec.europa.eu/info/research-and-innovation/funding/funding-opportunities/funding-programmes-and-open-calls/horizon-2020_en). This work was supported by Gorilla Awards in Behavioural Science who provided the Gorilla.sc licensing fee and an unlimited participant award to KG (https://gorilla.sc/).In the comparative study of human and nonhuman communication, ape gesturing provided the first demonstrations of flexible, intentional communication outside human language. Rich repertoires of these gestures have been described in all ape species, bar one: us. Given that the majority of great ape gestural signals are shared, and their form appears biologically inherited, this creates a conundrum: Where did the ape gestures go in human communication? Here, we test human recognition and understanding of 10 of the most frequently used ape gestures. We crowdsourced data from 5,656 participants through an online game, which required them to select the meaning of chimpanzee and bonobo gestures in 20 videos. We show that humans may retain an understanding of ape gestural communication (either directly inherited or part of more general cognition), across gesture types and gesture meanings, with information on communicative context providing only a marginal improvement in success. By assessing comprehension, rather than production, we accessed part of the great ape gestural repertoire for the first time in adult humans. Cognitive access to an ancestral system of gesture appears to have been retained after our divergence from other apes, drawing deep evolutionary continuity between their communication and our own.Publisher PDFPeer reviewe

Well-digging in a community of forest-living wild East African chimpanzees (Pan troglodytes schweinfurthii)

Funding was received for this research from the University of St Andrews and the Kirsten Scott Memorial Trust. The Budongo Conservation Field Station is supported by the Royal Zoological Society of Scotland. CH is supported by funding from the European Union’s 8th Framework Programme, Horizon 2020 (grant agreement no. 802719).Access to resources shapes species’ physiology and behaviour. Water is not typically considered a limiting resource for rainforest-living chimpanzees; however, several savannah and savannah-woodland communities show behavioural adaptations to limited water. Here, we provide a first report of habitual well-digging in a rainforest-living group of East African chimpanzees (Pan troglodytes schweinfurthii) and suggest that it may have been imported into the community’s behavioural repertoire by an immigrant female. We describe the presence and frequency of well-digging and related behaviour, and suggest that its subsequent spread in the group may have involved some degree of social learning. We highlight that subsurface water is a concealed resource, and that the limited spread of well-digging in the group may highlight the cognitive, rather than physical, challenges it presents in a rainforest environment.Publisher PDFPeer reviewe

The development of gestural communication in great apes

M.F. was funded by the Forschungskredit of the University of Zurich, grant no. FK-17-106.Great apes deploy gestural signals in goal-directed and flexible ways across a wide range of social contexts. Despite growing evidence for profound effects of developmental experience on social cognition, socio-ecological factors shaping gesture use are still poorly understood, particularly in apes living in their natural environment. After discussing current ambiguities in terminology and methods, we review recent work implementing a longitudinal and/or cross-sectional approach in great ape gesture acquisition and development. To understand whether and to what extent the socio-ecological environment influences gestural communication, it is essential to distinguish between the gesture repertoire and gesture usage, which represent different levels of analysis. While the majority of the apes’ gestural repertoire seems to be innate, accumulating evidence shows that the communicative usage of these signals is substantially affected by interactional experiences throughout ontogeny.PostprintPeer reviewe

GesturalOrigins : a bottom-up framework for establishing systematic gesture data across ape species

Funding: This research received funding from the European Union’s 8th Framework Programme, Horizon 2020, under grant agreement no 802719.Current methodologies present significant hurdles to understanding patterns in the gestural communication of individuals, populations, and species. To address this issue, we present a bottom-up data collection framework for the study of gesture: GesturalOrigins. By “bottom-up”, we mean that we minimise a priori structural choices, allowing researchers to define larger concepts (such as ‘gesture types’, ‘response latencies’, or ‘gesture sequences’) flexibly once coding is complete. Data can easily be re-organised to provide replication of, and comparison with, a wide range of datasets in published and planned analyses. We present packages, templates, and instructions for the complete data collection and coding process. We illustrate the flexibility that our methodological tool offers with worked examples of (great ape) gestural communication, demonstrating differences in the duration of action phases across distinct gesture action types and showing how species variation in the latency to respond to gestural requests may be revealed or masked by methodological choices. While GesturalOrigins is built from an ape-centred perspective, the basic framework can be adapted across a range of species and potentially to other communication systems. By making our gesture coding methods transparent and open access, we hope to enable a more direct comparison of findings across research groups, improve collaborations, and advance the field to tackle some of the long-standing questions in comparative gesture research.Publisher PDFPeer reviewe

The form and function of chimpanzee buttress drumming

We thank the Uganda National Council for Science and Technology, the President's Office, the Uganda Wildlife Authority and the National Forestry Authority for permission to conduct research, and the Royal Zoological Society of Scotland for their support of the field site. This research received funding from the European Union's 8th Framework Programme, Horizon 2020, under grant agreement no 802719.Many animal species use vocal and nonvocal acoustic signals to communicate over large distances. Wild chimpanzees, Pan troglodytes, drum on the buttress roots of trees, generating low-frequency sounds that can reach distances of over 1 km. Buttress drumming is produced in bouts of beats and is often accompanied by pant hoots, the species-typical long-distance vocalization. We investigated whether individual differences exist in the acoustic structure of drumming bouts produced by male chimpanzees of the Waibira community in the Budongo Forest in Uganda, and whether individual, contextual and social factors affected their use of drumming. We found individual differences in drumming bouts produced by seven male chimpanzees during travel events as well as in their timing within the pant hoot, and discriminated specific patterns of beats for some chimpanzees. In contrast, we found no evidence for individual differences in the acoustic structure of drumming bouts produced by four males during displays. Together these findings suggest that chimpanzees may be able to choose to encode identity within individual drumming ‘signatures’. Chimpanzees drummed less frequently as their party size increased. We found no evidence that the age of the signaller or the presence of preferred social partners, higher-ranking males or females in oestrus affected the use of drumming. These findings suggest there may be flexibility in buttress drumming across social and behavioural contexts and provide support for the hypothesis that, by encoding individual identity, long-distance drumming may be used to facilitate chimpanzee fission–fusion social dynamics.Publisher PDFPeer reviewe

Cat Hobaiter

Interview with Cat Hobaiter, who studies the evolution of communication, cognition and social behaviour in apes at the University of St Andrews and through field studies in the Budongo Forest in Uganda.</p

‘Adoption’ by maternal siblings in wild chimpanzees

This research was funded by the Leverhulme Trust Research Leadership Award F/00268/AP (http://www.leverhulme.ac.uk/), a Wenner-Gren Foundation Dissertation Fieldwork grant (http://www.wennergren.org/), the British Academy Grant SG411998 (http://www.brit.ac.uk) and the Royal Zoological Society of Scotland (http://www.rzss.org.uk). This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no. 283871. Genetic analyses were funded by the Max Planck Society, Boston University, and the Leakey Foundation.The adoption of unrelated orphaned infants is something chimpanzees and humans have in common. Providing parental care has fitness implications for both the adopter and orphan, and cases of adoption have thus been cited as evidence for a shared origin of an altruistic behaviour. We provide new data on adoptions in the free-living Sonso chimpanzee community in Uganda, together with an analysis of published data from other long-term field sites. As a default pattern, we find that orphan chimpanzees do not become adopted by adult group members but wherever possible associate with each other, usually as maternal sibling pairs. This occurs even if both partners are still immature, with older individuals effectively becoming ‘child household heads’. Adoption of orphans by unrelated individuals does occur but usually only if no maternal siblings or other relatives are present and only after significant delays. In conclusion, following the loss of their mother, orphaned chimpanzees preferentially associate along pre-existing social bonds, which are typically strongest amongst maternal siblings.Publisher PDFPeer reviewe

Socially learned habituation to human observers in wild chimpanzees

Fieldwork of CH and LS was funded by grants from the British Academy and a Leverhulme Trust’s Research Leadership Award.Abstract Habituation to human observers is an essential tool in animal behaviour research. Habituation occurs when repeated and inconsequential exposure to a human observer gradually reduces an animal’s natural aversive response. Despite the importance of habituation, little is known about the psychological mechanisms facilitating it in wild ani- mals. Although animal learning theory offers some account, the patterns are more complex in natural than in laboratory settings, especially in large social groups in which individual experiences vary and individuals influ- ence each other. Here, we investigate the role of social learning during the habituation process of a wild chim- panzee group, the Waibira community of Budongo Forest, Uganda. Through post hoc hypothesis testing, we found that the immigration of two well-habituated, young females from the neighbouring Sonso community had a significant effect on the behaviour of non-habituated Waibira indi- viduals towards human observers, suggesting that habitu- ation is partially acquired via social learning.PostprintPeer reviewe