Other voices: Gestural communication of wild Bonnet Macaques Macaca radiata in the Bandipur National Park, Southern India

Gestural communication in nonhuman primates (henceforth, primates) has been suggested to lie at the roots of human language, perhaps the most complex form of behaviour one encounters in the living world. Comparative studies, aimed at understanding shared features of language production and usage in phylogenetically related primate species, have revealed striking similarities in characteristics between primate gestures and human language, though with certain crucial dissimilarities. Gestures in apes, for instance, are used flexibly and intentionally, and develop ontogenetically during an individual’s lifetime, traits that typify human language. Gestures produced by wild apes, nevertheless, have rarely been reported to be referential, iconic or symbolic in nature, features that are hallmarks of human communication systems. The understanding of gestural communication in our closest living phylogenetic kin is mostly derived from apes while other non-ape primate species have been largely ignored in this context. Earlier attempts to investigate gestures in a few monkey species revealed the use of flexible and intentional gestures in captivity but again, such studies have rarely been conducted in the wild. Moreover, previous research on monkey gestures had not implemented the definitions and methods standardised in ape gestural research. Thus, it has not been possible to achieve a common understanding of gestural communication in apes and non-apes, which, in turn, is indispensible for comparative and evolutionary studies. In my doctoral dissertation, I intended to address some of these unexplored areas in monkey gesture research, which would eventually contribute to a fundamental understanding of primate gestures across taxa. I conducted my investigations in the Bandipur National Park in the state of Karnataka in southern India and attempted to explore the gestural communication system of bonnet macaques, an Old World cercopithecine primate endemic to peninsular India. Several free-ranging troops of the study species, particularly in the Bandipur population, have been continuously monitored over the past two decades, revealing the presence of extensive behavioural flexibility across individual members of these groups. Such characteristic lability in behavioural expression, displayed by this population of bonnet macaques, made it highly suitable for a potential inquiry into their communication systems, especially that of gestures. The first step towards an understanding of gestures in wild bonnet macaques necessitated, as outlined above, objective definitions of the gestural signals, adopted from the ape gesture literature. I followed the various criteria of flexibility and intentionality, postulated to distinguish gestures from other communicative signals during my study. The results of such an exercise revealed that bonnet macaques do indeed produce flexible and intentional gestures, manifest in the use of multiple gestures in a single context or a single gesture in multiple contexts and as persistent gesturing in the absence of an appropriate response from the audience until the signaller’s goals were achieved. My observations also indicated that some of the gestures might have been used by the macaques in a potentially referential, intentional manner, a hypothesis that demands further exploration in the future. In addition to the gestural repertoire of the study species, I also determined the functional meanings of each gesture, as revealed by the appropriateness of the recipient’s responses, aiding the signaller to achieve its original intended goal. Most of the gestures could be classified into distinct contextual categories, with the exception of a few, which were ubiquitously used across all several contexts, perhaps indicating their inherent flexibility. In order to further characterise the gestural repertoire of the macaques, I compared the age- and sex-specific gestural repertoires across my study individuals. There appeared to be significant differences in the repertoire sizes of individuals across age classes, with the affiliative and agonistic gestural repertoires significantly increasing and the play repertoire decreasing with progressing age. These results were indicative of gradual developmental processes leading to the ultimate adult repertoire in the species. Moreover, each study troop had distinct patterns of gestural repertoires across age classes, suggesting the influence of immediate socio-ecological factors in shaping the final gestural repertoire of the study troops. There was also a distinct variability in the repertoire sizes of adult females and males, with affiliative gestures being significantly more represented in the female repertoire than in that of the males. This perhaps reflects the variable social roles that members of each sex have been independently selected for during the evolution of the species. There were no significant influences of an individual’s social rank in the dominance hierarchy on the size of their gestural repertoires. Individual repertoire sizes did not vary significantly within an age-sex class and no idiosyncratic gestures could be identified in any subject, evoking the possibility of processes other than ontogenetic ritualisation to underlie the development of bonnet macaque gestural communication. Finally, there were several gestures that were used in a single context as well as single gestures deployed across contexts, confirming the flexible nature of gesture use by the study bonnet macaques. Similar analyses of age- and sex-based differences in the frequencies of gesture use revealed that juveniles displayed the highest frequencies of gestures across contexts. Affiliative gesturing was employed comparably across different age classes, agonistic gestures were used at relatively higher frequencies by adults while play gestures were more frequent among juveniles and infants. Amongst adult females and males, affiliative and agonistic gesturing were both higher in the females, possibly reflective of a typically female-bonded primate society. Play gestures, in contrast, were exhibited more by males, possibly due to the presence of subadults, these levels significantly decreasing with increasing age of the males. Gesture frequencies also varied amongst the age classes across the study troops, which could be attributed to their immediate social environments rather than their corresponding repertoire size. Affiliative gesturing was observed to be highest among adult female-infant pairs and adult female-female pairs, perhaps emerging from the close association of these two classes of individuals. Juveniles and infants appeared to direct play gestures significantly more towards members of their own age cohorts rather than towards one another. The social dominance ranks of signallers and recipients did not influence levels of affiliative gesturing within adult females or within adult males. Agonistic gestures, however, were more significantly directed down the dominance hierarchy in both sexes of the study macaques. Rank differences between adult individuals also did not affect the frequencies of gesturing towards one another in same-sex pairs. When the gestural profiles of infant and juvenile bonnet macaques were closely examined, I observed the frequencies of tactile gesture use to be comparable across all individuals while there was a gradual development of visual gestures from young infants to the older juveniles. Agonistic gestural repertoire size and the frequencies of use of such gestures were found to be significantly higher in older juveniles whereas affiliative and play gestures were comparable across these age categories. I then investigated the influence of certain innate factors such as individual age and repertoire size as well as certain social factors such as the mother’s social rank and frequencies of received contextual gestures on the processes underlying the development of gestures across my study infants and juveniles. Generalised linear modelling of these factors and their combinations indicated repertoire size and progressive age to significantly influence gesture use, particularly in the context of agonism. The levels of display of play gestures, in contrast, depended directly on the frequency of similar gestures received, indicating the importance of the surrounding social environment in the expression of such gesturing. These results indicate that processes other than ontogenetic ritualisation, which has been postulated to underlie the appearance of ape gestures, may be responsible for the development of gesturing in this macaque species. Finally, my study on bonnet macaques revealed the use of gesture sequences—gestures combined with other gestures or other signals—by individual subjects during their communicative acts. I investigated such sequences to unravel their conventional structures, if any, through Markov transition analyses and also attempted to understand the possible meanings of such sequences. My analyses revealed significant structural components in such sequences, with certain gestures invariably used either at the beginning or at the end of a particular sequence, with the former perhaps fulfilling the function of attracting the attention of target recipients. Certain gestures also had significantly higher probabilities of being associated with other particular gestures or signals, resulting in independent communicative networks constituted by affiliative-play or agonistic gestures. Although the functional meaning of such gesture sequences were not very apparent in every situation they were used in, they seemed to be significantly more effective in eliciting responses from targetted recipients, than were the same gestures repeatedly performed singly or other, functionally similar, single gestures, during persistent gesturing by signallers following an initial failure to evoke an appropriate response. What is clear, however, is that these gesture sequences, though an intrinsic component of the communication repertoire of bonnet macaques, do not appear to be functionally similar to the syntax of human language; their presence in the gestural repertoire of the species, nonetheless, should motivate us to design further studies in order to precisely determine their functions in the communication system of this macaque. In conclusion, my research is probably the first of its kind to explore the gestural communication of any non-ape species in its natural environment, systematically employing the standardised protocols of gesture research established in ape communication studies. This, I hope, will be a fundamental contribution to the scholarship of primate communication studies and in the process, open up exciting avenues in our endeavour to understand the evolution of primate gesturing, in general and the origins of human language, in particular

A wild boar hunting: Predation on a bonnet macaque by a wild boar in the Bandipur National Park, southern India

A ‘predator’ is defined as ‘an animal that naturally preys on others’1. Wild boars Sus scrofa are generally not recorded as natural predators of bonnet macaques, Macaca radiata. We report here an adult wild boar hunting and eating an adult bonnet macaque in the Reception area of the Bandipur National Park, Karnataka on 5 December 2013

Executive functions as a path to understanding nonhuman consciousness: Looking under the light

Consciousness in humans is best understood by the expression of individual goals and intentions, as expressed through language. The lack of a common language between humans and nonhuman animals and the historical tradition of attributing a mind exclusively to humans have, however, traditionally hindered the search for animal consciousness. Although conscious in the ordinary sense of wakefulness and in their ability to respond appropriately to stimuli, concrete evidence for more complex states of phenomenal or access consciousness await discovery in animals. Human behavioural expressions such as planning, monitoring, regulation of emotions, inhibition of actions, attentional flexibility, working memory, error detection, decision making and resolution of conflict, often collectively referred to as executive functions, have been considered behavioural proxies of different facets of human consciousness. These processes, the development of which correlates to the emergence of consciousness in humans, enable individuals to execute voluntary actions, make choices among alternatives and respond appropriately to novel situations to achieve short- and long-term goals. Given the history of our vain search for consciousness as a singular phenomenon in animals, we should perhaps explore the structure and organization of basic executive functions as potential building blocks of consciousness in nonhuman species. It is likely that such processes in animals differ from those in humans only in degree and not in kind and that such a functional understanding of executive functions could better illuminate the development and evolution of the conscious human mind

Gestural communication of wild bonnet macaques in the Bandipur National Park, Southern India

Nonhuman primate gestures are believed to be crucial evolutionary precursors of human language. Comparative studies on primate gestures in an evolutionary framework have, however, remained largely restricted to the great apes and the potential flexibility and richness of gestural communication in monkeys, especially in the wild, continue to be virtually unknown. In this paper, we followed several criteria, adapted from ape gesture studies, to identify gestures and evaluate their contexts of usage in the repertoire of wild bonnet macaques Macaca radiata in the Bandipur National Park of southern India. This report is the first of its kind to systematically identify gestures in any wild, non-ape species, thus providing a platform for comparative studies across primate taxa, particularly in our efforts to trace out the phylogenetic origins of language-like markers in the primate lineage, earlier than in the great apes

Creativity and experience in nonhuman primate communication

The word creativity, coined undoubtedly for human achievement, has perhaps never been applied to the behaviour of nonhuman species. Whether this was simply to avoid the threat of anthropomorphism or whether there are qualitative differences between the innovative behaviours of nonhuman and human animals that would preclude the former from being included in the category of creative beings remains an open question. There has, however, been a growing interest in creative behaviours in nonhuman species since Lloyd Morgan (1912). Morgan observed that the behavioural repertoire of every animal consisted of two kinds of behaviour, some repetitive and a small proportion of novel behaviours, which were distinctly different from the former regular behaviours. It is this second kind of behaviour that interests us here

Not here, there! Possible referential gesturing during allogrooming by wild bonnet macaques, Macaca radiata

Intentional referential gestures, a fundamental building block of symbolic human language, have been reported from a range of species, including non-human primates. While apes are known to spontaneously use intentional gestures, only captive macaques, amongst nonape primates, appear to intentionally display learnt gestures. On the other hand, referential gestures have so far been reported only in chimpanzees, amongst non-human primates. We document here, for the first time, potentially referential gesturing, used intentionally as well, in a monkey species, the bonnet macaque Macaca radiata, in the wild. Bonnet macaques use four distinct actions during allogrooming, possibly to indicate a particular body part intended to be groomed. These acts were successful in drawing the recipients’ attention to the indicated part, which they began to groom subsequently. This study enriches our understanding of non-ape primate gestural communication and adds to the growing evidence for early human language-like capacities in non-human species

Watering holes: The use of arboreal sources of drinking water by Old World monkeys and apes

Water is one of the most important components of an animal's diet, as it is essential for life. Primates, as do most animals, procure water directly from standing or free-flowing sources such as pools, ponds and rivers, or indirectly by the ingestion of certain plant parts. The latter is frequently described as the main source of water for predominantly arboreal species. However, in addition to these, many species are known to drink water accumulated in tree-holes. This has been commonly observed in several arboreal New World primate species, but rarely reported systematically from Old World primates. Here, we report observations of this behaviour from eight great ape and Old World monkey species, namely chimpanzee, orangutan, siamang, western hoolock gibbon, northern pig-tailed macaque, bonnet macaque, rhesus macaque and the central Himalayan langur. We hypothesise three possible reasons why these primates drink water from tree-holes: (1) coping with seasonal or habitat-specific water shortages, (2) predator/human conflict avoidance, and (3) potential medicinal benefits. We also suggest some alternative hypotheses that should be tested in future studies. This behaviour is likely to be more prevalent than currently thought, and may have significant, previously unknown, influences on primate survival and health, warranting further detailed studies. (C) 2016 Elsevier B.V. All rights reserved

Dominance Style and Vocal Communication in Primates

International audienc

Dominance style is a key predictor of vocal use and evolution across nonhuman primates

Animal communication has long been thought to be subject to pressures and constraints associated with social relationships. However, our understanding of how the nature and quality of social relationships relates to the use and evolution of communication is limited by a lack of directly comparable methods across multiple levels of analysis. Here, we analysed observational data from 111 wild groups belonging to 26 non-human primate species, to test how vocal communication relates to dominance style (the strictness with which a dominance hierarchy is enforced, ranging from ‘despotic’ to ‘tolerant’). At the individual-level, we found that dominant individuals who were more tolerant vocalized at a higher rate than their despotic counterparts. This indicates that tolerance within a relationship may place pressure on the dominant partner to communicate more during social interactions. At the species-level, however, despotic species exhibited a larger repertoire of hierarchyrelated vocalizations than their tolerant counterparts. Findings suggest primate signals are used and evolve in tandem with the nature of interactions that characterize individuals’ social relationships.https://royalsocietypublishing.org/journal/rsosMammal Research Institut