Able-bodied wild chimpanzees imitate a motor procedure used by a disabled individual to overcome handicap

Fieldwork of CH was generously supported by grants from the Wenner-Gren Foundation (http://wennergren.org) and the Russell Trust. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Chimpanzee culture has generated intense recent interest, fueled by the technical complexity of chimpanzee tool-using traditions; yet it is seriously doubted whether chimpanzees are able to learn motor procedures by imitation under natural conditions. Here we take advantage of an unusual chimpanzee population as a 'natural experiment' to identify evidence for imitative learning of this kind in wild chimpanzees. The Sonso chimpanzee community has suffered from high levels of snare injury and now has several manually disabled members. Adult male Tinka, with near-total paralysis of both hands, compensates inability to scratch his back manually by employing a distinctive technique of holding a growing liana taut while making side-to-side body movements against it. We found that seven able-bodied young chimpanzees also used this 'liana-scratch' technique, although they had no need to. The distribution of the liana-scratch technique was statistically associated with individuals' range overlap with Tinka and the extent of time they spent in parties with him, confirming that the technique is acquired by social learning. The motivation for able-bodied chimpanzees copying his variant is unknown, but the fact that they do is evidence that the imitative learning of motor procedures from others is a natural trait of wild chimpanzees.Publisher PDFPeer reviewe

Esperienze e forme di scrittura online

L’esperienza dello scrivere online varia in misura notevole col variare delle forme e dei contesti di comunicazione in cui si dà a vedere. Prendendo in esame quattro ambienti di comunicazione scritta online (non unidirezionali) – posta elettronica, Twitter, chat, gruppi di discussione – è possibile far emergere alcuni tratti distintivi, riguardanti le strategie e gli stili di scrittura. Un fattore differenziale di cui tenere conto è anche la relazione tra scrittura e tempo, ovvero le diverse attese in termini di durata e permanenza del testo scritto

Wild chimpanzees' use of single and combined vocal and gestural signals

We describe the individual and combined use of vocalizations and gestures in wild chimpanzees. The rate of gesturing peaked in infancy and, with the exception of the alpha male, decreased again in older age groups, while vocal signals showed the opposite pattern. Although gesture-vocal combinations were relatively rare they were consistently found in all age groups, especially during affiliative and agonistic interactions. Within behavioural contexts rank (excluding alpha-rank) had no effect on the rate of male chimpanzees’ use of vocal or gestural signals and only a small effect on their use of combination signals. The alpha male was an outlier, however, both as a prolific user of gestures and recipient of high levels of vocal and gesture-vocal signals. Persistence in signal use varied with signal type: chimpanzees persisted in use of gestures and gesture vocal combinations after failure, but where their vocal signals failed they tended to add gestural signals to produce gesture-vocal combinations. Overall, chimpanzees employed signals with a sensitivity to the public/private nature of information, by adjusting their use of signal types according to social context and by taking into account potential out of-sight audiences. We discuss these findings in relation to the various socio-ecological challenges that chimpanzees are exposed to in their natural forest habitats and the current discussion of multimodal communication in great apes.Publisher PDFPeer reviewe

Reindeer and the quest for Scottish enlichenment

Funding Information: The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Data were collected with funding from the Goodman Fund, Dartmouth College and the Global Fellowship Scheme, University of St Andrews.In the hall of animal oddities, the reindeer (Rangifer tarandus) is the only mammal with a color-shifting tapetum lucidum and the only ruminant with a lichen-dominated diet. These puzzling traits coexist with yet another enigma––ocular media that transmit up to 60% of ultraviolet (UV) light, enough to excite the cones responsible for color vision. It is unclear why any day-active circum-Arctic mammal would benefit from UV visual sensitivity, but it could improve detection of UV-absorbing lichens against a background of UV-reflecting snows, especially during the extended twilight hours of winter. To explore this idea and advance our understanding of reindeer visual ecology, we recorded the reflectance spectra of several ground-growing (terricolous), shrubby (fruticose) lichens in the diets of reindeer living in Cairngorms National Park, Scotland.Publisher PDFPeer reviewe

Object use in communication of semi-wild chimpanzees

Catherine Hobaiter’s research work is funded under the European Union’s 8th Framework Programme under grant agreement 802719. The research of Marina Davila-Ross is funded by Leakey Foundation Research Grant and Royal Society Research Grant (RG140282).Object interactions play an important role in human communication but the extent to which nonhuman primates incorporate objects in their social interactions remains unknown. To better understand the evolution of object use, this study explored how objects are used in social interactions in semi-wild chimpanzees (Pan troglodytes). We used an observational approach focusing on naturally occurring object actions where we examined their use and tested whether the production of object actions was influenced by the recipients' visual attention as well as by colony membership. The results show that chimpanzees adjusted both the type of object used, and the modality of object actions to match the visual attention of the recipient, as well as colony differences in the use of targeted object actions. These results provide empirical evidence highlighting that chimpanzees use objects in diverse ways to communicate with conspecifics and that their use may be shaped by social factors, contributing to our understanding of the evolution of human nonverbal communication, language, and tool use.Publisher PDFPeer reviewe

What is a gesture? A meaning-based approach to defining gestural repertoires

Fieldwork of CH was generously supported by the Wenner Gren Foundation, the Russel Trust, and the British Academy.Current systems of categorizing ape gestures are typically subjective, relying on human intuition. We have systematized the features on which categorization depends (movement; body part; one/both limbs; use of detached object; rhythmic repetition; contact with recipient), showing that a potential repertoire of over 1000 gestures is physically possible, as large as the lexicon of some languages. In contrast, little more than a tenth of these gestures is used in chimpanzee communication. The striking overlaps in repertoire found between populations and even species of great ape are evidently not a result of a restricted set of possible gestures. Using the reactions of signallers to identify which gestures are intended to be different by the apes themselves, we revised the current classification, making some new distinctions and abolishing others previously considered important, giving a final repertoire of 81. A small number of gestures are used deictically, such that the recipient must pay attention to specific locations to satisfy the signaller; raising the possibility of a stepping-stone to the evolution of reference.PostprintPeer reviewe

Bonobo and chimpanzee gestures overlap extensively in meaning

Funding: JSPS Core-to-Core Program http://www.jsps.go.jp/english/e-core_to_core/ (grant number 2012-2014, 2015-2017). Japan Society for the Promotion of Science Grant in Aid for Scientific Research (grant number 25304019, 25257407, 26257408). University of St Andrews https://www.st-andrews.ac.uk/study/ug/fees-and-funding/scholarships/600th-wardlaw/ (grant number 600th Anniversary Scholarship). Wenner-Gren Foundation http://www.wennergren.org/ (grant number Gr. 8950).Cross-species comparison of great ape gesturing has so far been limited to the physical form of gestures in the repertoire, without questioning whether gestures share the same meanings. Researchers have recently catalogued the meanings of chimpanzee gestures, but little is known about the gesture meanings of our other closest living relative, the bonobo. The bonobo gestural repertoire overlaps by approximately 90% with that of the chimpanzee, but such overlap might not extend to meanings. Here, we first determine the meanings of bonobo gestures by analysing the outcomes of gesturing that apparently satisfy the signaller. Around half of bonobo gestures have a single meaning, while half are more ambiguous. Moreover, all but 1 gesture type have distinct meanings, achieving a different distribution of intended meanings to the average distribution for all gesture types. We then employ a randomisation procedure in a novel way to test the likelihood that the observed between-species overlap in the assignment of meanings to gestures would arise by chance under a set of different constraints. We compare a matrix of the meanings of bonobo gestures with a matrix for those of chimpanzees against 10,000 randomised iterations of matrices constrained to the original data at 4 different levels. We find that the similarity between the 2 species is much greater than would be expected by chance. Bonobos and chimpanzees share not only the physical form of the gestures but also many gesture meanings.Publisher PDFPeer reviewe

Variation in hunting behaviour in neighbouring chimpanzee communities in the Budongo forest, Uganda

This research was funded by the Leverhulme Trust Research Leadership Award F/00268/AP (http://www.leverhulme.ac.uk/) and the British Academy grant SG411998 (http://www.brit.ac.uk). An additional data set with all remaining data are now available at https://figshare.com/articles/DATA_hunting_xlsx/5004071Hunting and sharing of meat is seen across all chimpanzee sites, with variation in prey preferences, hunting techniques, frequencies, and success rates. Here, we compared hunting and meat-eating behaviour in two adjacent chimpanzee communities (Pan troglodytes schweinfurthii) of Budongo Forest, Uganda: the Waibira and Sonso communities. We observed consistent between-group differences in prey-species preferences and in post-hunting behaviour. Sonso chimpanzees show a strong prey preference for Guereza colobus monkeys (Colobus guereza occidentalis; 74.9% hunts), and hunt regularly (1–2 times a month) but with large year-to-year and month-to-month variation. Waibira chimpanzee prey preferences are distributed across primate and duiker species, and resemble those described in an early study of Sonso hunting. Waibira chimpanzees (which include ex-Sonso immigrants) have been observed to feed on red duiker (Cephalophus natalensis; 25%, 9/36 hunts), a species Sonso has never been recorded to feed on (18 years data, 27 years observations), despite no apparent differences in prey distribution; and show less rank-related harassment of meat possessors. We discuss the two most likely and probably interrelated explanations for the observed intergroup variation in chimpanzee hunting behaviour, that is, long-term disruption of complex group-level behaviour due to human presence and possible socially transmitted differences in prey preferences.Publisher PDFPeer reviewe

Multimodal communication and audience directedness in the greeting behaviour of semi-captive African savannah elephants

This research was funded by the Austrian Science Fund (FWF) [AW0126211] and the European Union’s 8th Framework Programme, Horizon 2020 [802719].Many species communicate by combining signals into multimodal combinations. Elephants live in multi-level societies where individuals regularly separate and reunite. Upon reunion, elephants often engage in elaborate greeting rituals, where they use vocalisations and body acts produced with different body parts and of various sensory modalities (e.g., audible, tactile). However, whether these body acts represent communicative gestures and whether elephants combine vocalisations and gestures during greeting is still unknown. Here we use separation-reunion events to explore the greeting behaviour of semi-captive elephants (Loxodonta africana). We investigate whether elephants use silent-visual, audible, and tactile gestures directing them at their audience based on their state of visual attention and how they combine these gestures with vocalisations during greeting. We show that elephants select gesture modality appropriately according to their audience’s visual attention, suggesting evidence of first-order intentional communicative use. We further show that elephants integrate vocalisations and gestures into different combinations and orders. The most frequent combination consists of rumble vocalisations with ear-flapping gestures, used most often between females. By showing that a species evolutionarily distant to our own primate lineage shows sensitivity to their audience’s visual attention in their gesturing and combines gestures with vocalisations, our study advances our understanding of the emergence of first-order intentionality and multimodal communication across taxa.Peer reviewe

A socio-ecological perspective on the gestural communication of great ape species, individuals, and social units

Over the last 30 years, most research on non-human primate gestural communication has been produced by psychologists, which has shaped the questions asked and the methods used. These researchers have drawn on concepts from philosophy, linguistics, anthropology, and ethology, but despite these broad influences the field has neglected to situate gestures into the socio-ecological context in which the diverse species, individuals, and social-units exist. In this review, we present current knowledge about great ape gestural communication in terms of repertoires, meanings, and development. We fold this into a conversation about variation in other types of ape social behaviour to identify areas for future research on variation in gestural communication. Given the large variation in socio-ecological factors across species and social-units (and the individuals within these groups), we may expect to find different preferences for specific gesture types; different needs for communicating specific meanings; and different rates of encountering specific contexts. New tools, such as machine-learning based automated movement tracking, may allow us to uncover potential variation in the speed and form of gesture actions or parts of gesture actions. New multi-group multi-generational datasets provide the opportunity to apply analyses, such as Bayesian modelling, which allows us to examine these rich behavioural landscapes. Together, by expanding our questions and our methods, researchers may finally be able to study great ape gestures from the perspective of the apes themselves and explore what this gestural communication system reveals about apes’ thinking and experience of their world.Publisher PDFPeer reviewe