Intentional gestural communication amongst red-capped mangabeys (Cercocebus torquatus)

Apes, human’s closest living relatives, are renowned for their intentional and highly flexible use of gestural communication. In stark contrast, evidence for flexible and intentional gestural communication in monkeys is scarce. Here, we investigated the intentionality and flexibility of spontaneous gesture use in red-capped mangabeys (Cercocebus torquatus). We applied established methods used in ape gesture research to analyse whether the body acts produced by a total of 17 individuals living in three different groups in captivity qualified as intentionally produced gesture instances. Results showed that signallers showed all hallmarks of intentionality during the production of 20 out of a total of 21 different types of body acts. These were only produced in the presence of other individuals, and the monkeys showed audience checking, sensitivity to the attentional states of recipients, adjustment of signal modality, and response waiting relative to their production. Moreover, in case of communication failure, the monkeys showed goal persistence, and regarding the production contexts they showed some signs of means–ends dissociation. Therefore, these monkeys are capable of flexible and intentional gestural communication and use this to communicate with conspecifics. Our results corroborate recent findings showing that intentional gestural communication was already present in the monkey lineage of catarrhine primates. We discuss our results in light of the comparative approach towards human language evolution and highlight our finding that these monkeys also showed flexible and intentional use of four ‘free’ manual gesture types

Correlates of social role and conflict severity in wild vervet monkey agonistic screams

This work was funded by the European Research Council under the European Union′s Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement n° 283871 (https://ec.europa.eu/research/fp7/index_en.cfm) and the Swiss National Science Foundation (Project 310030_143359; http://www.snf.ch/en/funding). EW was funded by the Swiss National Science Foundation (P300P3_151187 and 31003A_159587) and the Branco Weiss Fellowship - Society in Science (https://brancoweissfellowship.org/). Data and codes are available on Figshare at https://figshare.com/articles/Correlates_of_social_role_and_conflict_severity_in_wild_vervet_monkey_agonistic_screams/5413975 (DOI: 10.6084/m9.figshare.5413975).Screams are acoustically distinct, high-pitched and high-amplitude calls, produced by many social species. Despite a wide range of production contexts, screams are characterised by an acoustic structure that appears to serve in altering the behaviour of targeted receivers during agonistic encounters. In chimpanzees, this can be achieved by callers producing acoustic variants that correlate with their identity, social role, relationship with the targeted recipient, the composition of the audience and the nature of the event. Although vervet monkeys (Chlorocebus pygerythrus) have been studied for decades, not much is known about their agonistic screams. Here, we examined agonistic screams produced by wild vervet monkeys to investigate the degree to which caller identity, social role and conflict severity affected call structure. We found that screams were both individually distinctive and dependent of the agonistic events. In particular, victim screams were longer and higher-pitched than aggressor screams, while screams produced in severe conflicts (chases, physical contact) had higher entropy than those in mild conflicts. We discuss these findings in terms of their evolutionary significance and suggest that acoustic variation might serve to reduce the aggression level of opponents, while simultaneously attracting potential helpers.Publisher PDFPeer reviewe

Social learning rulles and their adaptive functions in wild vervet monkeys

Social learning is the mechanism that allows the transmission of specific behaviours inside a social unit, i.e. the formation of traditions. Recent studies have revealed the presence of social learning in a wide range of species and taxa. However, despite a substantial number of studies on social learning in animais, little attention has so far been given to social learning stratégies: why, when, what and from whom individuals learn socially. We therefore studied the social learning rules and their adaptive functions in multiple groups of wild vervet monkeys (Chlorocebus pygerythrus) from the same population, at the Inkawu Vervet Project within the Mawana game reserve, in South Africa. In the first study, we demonstrated the presence of an interaction between différent social learning stratégies used by vervet monkeys, in a field experiment where an adult maie model obtained a much higher payoff out of a foraging box than an adult female model (the model preferred by naïve group members). In the s&me experiment, we also looked at the évolution of the use of these social learning stratégies by vervet monkeys. We analysed the trade-off between social and asocial learning, giving particular focus to the benefits of learning stratégies. With this first experiment, we highlighted the behavioral flexibility of the dispersing sex in vervet monkeys and suggest that the philopatric sex can afford to be more conservative in their social learning. We demonstrated that multiple social-learning biases can coexist and interact within the same species. Second, using another experimental paradigm, we examined the spatial memory and learning abilities of wild vervet monkeys to try to understand from a functional perspective why vervet monkeys preferentially use females as a model to learn socially. Monkeys learned the association between the presence of food in two buckets placed in différent locations. This experiment shows that both sexes learn the location of a new food resource after only a single training bout and remember this location on the long term, but females did not outperform maies. Thus, females must be a preferred model due to their potential greater général knowledge about resources in the territory. Finally, we observed gestural communication in adult female vervet monkeys during social interactions and analysed the behavioural variation between neighbouring groups of the same population. We found that the behavioural variation found in our study is not consistent with expectations based on ecological or genetic différences. Therefore, social factors might underlie the différences found in the way vervet monkeys use their gestural repertoire, and we argue that this behavioural variation might be learned socially and thus might resuit in group-level traditions in this population of wild vervet monkeys. We conclude that field experiments are an excellent and underused tool to gain more knowledge in this domain of research, and we encourage researchers to conduct similar field experiments in différent species and taxa, as learning more about the évolution and underlying mechanisms of cultural behaviour in animais might help us to better understand our own cumulative culture and arbitrary traditions. --- De récentes études ont révélé la présence d'apprentissage sociale chez un grand nombre d'espèces et taxons. L'apprentissage sociale est le mécanisme qui permet la formation de tradition, par ,1a transmission de comportements spécifiques au sein d'une unité sociale. La recherche a identifié en détail les mécanismes sous-jacents l'apprentissage sociale et à démontrer l'envergure de techniques arbitraires aux seins des groupes, donnant lieu aux traditions. Cependant, certaines de ces questions restent encore sous-étudiées, comme « pourquoi, quand, quoi et de qui » les individus apprennent-ils socialement. Nous avons donc étudié les règles d'apprentissage social et leurs fonctions adaptatives chez des groupes de singes vervets sauvages (Chlorocebus pygerythrus) appartenant à la même population, au projet 'Inkawu Vervet' dans la réserve de chasse de Mawana, en Afrique du Sud. Nous avons d'abord examiné les stratégies d'apprentissage social utilisées par les singes vervet, dans le cadre d'une première expérience sur le terrain. Dans cette expérience, un modèle maie obtenait en ouvrant une boîte une meilleure récompense, alimentaire qu'un modèle femelle. Nous avons ensuite analysé le compromis entre apprentissage social et apprentissage asocial, en mettant un accent particulier sur les fonctions adaptatives de l'apprentissage social. Avec cette première expérience, nous avons mis en évidence la flexibilité comportementale des individus migrateur (les maies) chez les singes vervets et nous avons montré que les individus philopatrique (les femelles) sont plus conservateurs dans leur façon d'apprendre socialement. Nous avons démontré que de multiples biais d'apprentissage social peuvent coexister et interagir au sein d'une même espèce. Dans une seconde expérience, nous avons examiné la mémoire spatiale et les capacités d'apprentissage des singes vervets sauvages pour tenter de comprendre d'un point de vue fonctionnel pourquoi les singes vervets utilisent préférentiellement les femelles comme modèle d'apprentissage social. Les singes ont appris le lien entre la présence de nourriture dans deux seaux situés à des endroits différents. Cette expérience a montré que les deux sexes ont appris l'emplacement d'une nouvelle ressource alimentaire après un seul entrainement et se sont souvenus de cet endroit sur le long terme. Enfin, nous avons observé la communication gestuelle des femelles vervets adultes lors d'interactions sociales avec d'autres femelles vervets adultes. Nous avons analysé les variations comportementales entre des groupes voisins de singes de la même population. Nous avons supposé que la variation comportementale observée dans notre étude, ne pouvait être expliquée ni par des facteurs écologiques, ni par des facteurs génétiques. Par conséquent, les facteurs sociaux pourraient être à la base des différences observées dans la manière dont les singes vervets utilisent leur répertoire gestuel. Finalement, nous incitons les chercheurs à poursuivre ses expériences sur le terrain pour acquérir plus de connaissances dans ce domaine de recherche, et ceci concernant différentes espèces et taxons, car en apprendre davantage sur l'évolution et les mécanismes sous-jacents les comportements culturels des animaux pourrait nous aider à mieux comprendre notre propre culture cumulative et nos traditions arbitraires

Intentional gestural signalling amongst red-capped mangabeys (Cercocebus torquatus)

International audienceApes, human's closest living relatives, are renowned for their intentional and highly flexible use of gestural signals In stark contrast, evidence for intentional signalling in monkeys is scant, especially when considering signals produced amongst conspecifics. We present data on the naturally occurring gestural communication amongst captive red-capped mangabeys (Cercocebus torquatus), collected from a total of 17 Individuals living in three different groups at the Station Biologique, Paimpont, France. When applying methods originally established in ape gesture research to assess whether these monkeys used ‘markers of intentionality’ during their gesture production, we found that 24 out of a total of 25 different signal types (including 4 facial expressions and 5 manual gestures) qualified as intentional. They were characterized by sensitivity to the attentional state of recipients, adjustment to audience effects, and goal persistence. Our results reveal that monkey communication is cognitively more complex than previously assumed, and show that the precursors to flexible and intentional communication were already present in the primate lineage around 30 My ago

Complexity in monkey communication: gestural signaling in red-capped mangabeys (Cercocebus torquatus) is intentional

International audienc

Intentional gestural communication amongst red-capped mangabeys (Cercocebus torquatus)

International audienceApes, human’s closest living relatives, are renowned for their intentional and highly flexible use of gestural communication. In stark contrast, evidence for flexible and intentional gestural communication in monkeys is scarce. Here, we investigated the intentionality and flexibility of spontaneous gesture use in red-capped mangabeys (Cercocebus torquatus). We applied established methods used in ape gesture research to analyse whether the body acts produced by a total of 17 individuals living in three different groups in captivity qualified as intentionally produced gesture instances. Results showed that signallers showed all hallmarks of intentionality during the production of 20 out of a total of 21 different types of body acts. These were only produced in the presence of other individuals, and the monkeys showed audience checking, sensitivity to the attentional states of recipients, adjustment of signal modality, and response waiting relative to their production. Moreover, in case of communication failure, the monkeys showed goal persistence, and regarding the production contexts they showed some signs of means-ends dissociation. Therefore, these monkeys are capable of flexible and intentional gestural communication and use this to communicate with conspecifics. Our results corroborate recent findings showing that intentional gestural communication was already present in the monkey lineage of catarrhine primates. We discuss our results in light of the comparative approach towards human language evolution and highlight our finding that these monkeys also showed flexible and intentional use of four ’free’ manual gesture types

Correlates of social role and conflict severity in wild vervet monkey agonistic screams

Screams are acoustically distinct, high-pitched and high-amplitude calls, produced by many social species. Despite a wide range of production contexts, screams are characterised by an acoustic structure that appears to serve in altering the behaviour of targeted receivers during agonistic encounters. In chimpanzees, this can be achieved by callers producing acoustic variants that correlate with their identity, social role, relationship with the targeted recipient, the composition of the audience and the nature of the event. Although vervet monkeys (Chlorocebus pygerythrus) have been studied for decades, not much is known about their agonistic screams. Here, we examined agonistic screams produced by wild vervet monkeys to investigate the degree to which caller identity, social role and conflict severity affected call structure. We found that screams were both individually distinctive and dependent of the agonistic events. In particular, victim screams were longer and higher-pitched than aggressor screams, while screams produced in severe conflicts (chases, physical contact) had higher entropy than those in mild conflicts. We discuss these findings in terms of their evolutionary significance and suggest that acoustic variation might serve to reduce the aggression level of opponents, while simultaneously attracting potential helpers

Intentional gestural communication amongst red-capped mangabeys (Cercocebus torquatus)

Apes, human’s closest living relatives, are renowned for their intentional and highly flexible use of gestural communication. In stark contrast, evidence for flexible and intentional gestural communication in monkeys is scarce. Here, we investigated the intentionality and flexibility of spontaneous gesture use in red-capped mangabeys (Cercocebus torquatus). We applied established methods used in ape gesture research to analyse whether the body acts produced by a total of 17 individuals living in three different groups in captivity qualified as intentionally produced gesture instances. Results showed that signallers showed all hallmarks of intentionality during the production of 20 out of a total of 21 different types of body acts. These were only produced in the presence of other individuals, and the monkeys showed audience checking, sensitivity to the attentional states of recipients, adjustment of signal modality, and response waiting relative to their production. Moreover, in case of communication failure, the monkeys showed goal persistence, and regarding the production contexts they showed some signs of means–ends dissociation. Therefore, these monkeys are capable of flexible and intentional gestural communication and use this to communicate with conspecifics. Our results corroborate recent findings showing that intentional gestural communication was already present in the monkey lineage of catarrhine primates. We discuss our results in light of the comparative approach towards human language evolution and highlight our finding that these monkeys also showed flexible and intentional use of four ‘free’ manual gesture types