Gestures in nonhuman primate communication, especially those of apes, were thereafter defined as "discrete, mechanically ineffective, physical movements of the body" (Hobaiter and Byrne 2011a; Genty et al. 2009; Cartmill and Byrne 2010) or "communicative signals produced by body postures or the movement of body parts, including the limbs, head and /or facial muscles to achieve an intended goal" (Tomasello and Call 2007). It has also been suggested that gestures should be signals always directed to a particular recipient and be mechanically ineffective in eliciting voluntary responses from the recipient (Arbib, Liebal, and Pika 2008; Pika 2008; Schel et al. 2013). Currently, summarising from the literature, a generally accepted operational definition of "gesture" (in the great ape literature) is: a discrete, mechanically ineffective movement of body parts deployed intentionally (with the aim of eliciting a behavioural response from the recipient).Like the study of tool use in nonhuman animals, research on great ape behaviour has frequently led to the discovery of similar behaviour in other primates. A recent review of ape gestures, compiling findings from the past six decades, supports the hypothesis that gestures constitute innate signals which can be used in intentional ways to convey particular meaning in communicative contexts (Byrne et al. 2017). As gesture forms appear phylogenetically continuous among apes, it is quite possible that similar gestural communication may be encountered in non-ape primate species as well.Unfortunately, earlier investigations of gestural communication in macaques did not use the same operational definitions of "gesture", as stated above (

Comparative studies of nonhuman communication systems could provide insights into the origins and evolution of a distinct dimension of human language: intentionality. Recent studies have provided evidence for intentional communication in different species but generally in captive settings. We report here a novel behaviour of food requesting from humans displayed by wild bonnet macaques Macaca radiata, an Old World cercopithecine primate, in the Bandipur National Park of southern India. Using both natural observations and field experiments, we examined four different behavioural components—coo-calls, hand-extension gesture, orientation, and monitoring behaviour—of food requesting for their conformity with the established criteria of intentional communication. Our results suggest that food requesting by bonnet macaques is potentially an intentionally produced behavioural strategy as all the food requesting behaviours except coo-calls qualify the criteria for intentionality. We comment on plausible hypotheses for the origin and spread of this novel behavioural strategy in the study macaque population and speculate that the cognitive precursors for language production may be manifest in the usage of combination of signals of different modalities in communication, which could have emerged in simians earlier than in the anthropoid apes.

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 hierarchy-related 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.

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.