Primates live in complex social systems with social structures ranging from more to less despotic. In less despotic species, dominance might impose fewer constraints on social choices, tolerance is greater than in despotic species and subordinates may have little need to include novel food items in the diet (i.e. neophilia), as contest food competition is lower and resources more equally distributed across group members. Here, we used macaques as a model to assess whether different dominance styles predict differences in neophilia and social tolerance over food. We provided familiar and novel food to 4 groups of wild macaques (N = 131) with different dominance styles (Macaca fuscata, M. fascicularis, M. sylvanus, M. maura). Our study revealed inter- and intra-specific differences in individuals’ access to food, which only partially reflected the dominance styles of the study subjects. Contrary to our prediction, social tolerance over food was higher in more despotic species than in less despotic species. Individuals with a higher dominance rank and being better socially integrated (i.e. higher Eigenvector centrality) were more likely to retrieve food in all species, regardless of their dominance style. Partially in line with our predictions, less integrated individuals more likely overcame neophobia (as compared to more integrated ones), but only in species with more tolerance over food. Our study suggests that individual characteristics (e.g. social integration or personality) other than dominance rank may have a stronger effect on an individual’s access to resources.

Play is widespread across mammalian taxa, but species strongly vary in the ways they play. In less despotic primate species (i.e., with less steep dominance hierarchies, less severe conflicts, and more reconciliation), play has been described as being more frequent, cooperative, and freely expressed. To study the link between social play and dominance style, we compared play behavior in free-ranging infants, juveniles and subadults of more despotic Japanese macaques (Macaca fuscata, N = 24) and less despotic moor macaques (Macaca maura, N = 17). We found interspecific differences in play behavior that corresponded with the contrasting dominance styles of the study species, largely confirming our predictions. In particular, moor macaques spent a larger proportion of time in solitary and social play than Japanese macaques, while Japanese macaques spent a larger proportion of time in grooming interactions. In moor macaques, play sessions included more players, a larger variety of play behaviors, greater play face rates, a greater proportion of time in contact play, and a higher rate of reciprocal play-biting than in Japanese macaques. Aggressive escalations were not common, but more frequent in Japanese macaques. Finally, a higher frequency of play faces during play sessions predicted the occurrence of more reciprocal play-bites, but not the proportion of time spent in contact play behaviors. Additional studies on other groups and species will allow a better understanding of the link between dominance style and social play.

In several species, rank predicts access to food, and subordinates may need specific behavioural strategies to get a share of resources. This may be especially important in despotic species, where resources are strongly biased in favour of dominants and subordinates may more strongly rely on specific tactics to maximize food intake. Here, we compared three macaque species with an experimental set-up reproducing feeding competition contest. Following our predictions, more tolerant species mostly retrieved food in the presence of others and were less dependent on specific tactics. Contrarily, subordinates in more despotic species more likely collected food (1) when dominants could not see food or (2) were attacking others, (3) while “dissimulating”, or (4) “storing food”. Our study reveals that dominance styles reliably predict the probability of using specific food retrieval tactics and provides important insights on the social conditions that might have led to the emergence of tactical deception.

Group living is beneficial for individuals, but also comes with costs. One such cost is the increased possibility of pathogen transmission, because increased numbers or frequencies of social contacts is often associated with increased parasite abundance or diversity. The social structure of a group or population has been shown to be paramount to patterns of infection and transmission. Yet, for various reasons, studies investigating the social transmission of parasites in animals, and especially in primates, have only taken into account parts of the group (e.g., only adults or even only adult females), which is likely to impact the interpretation of any results linking sociality and parasitism. Here, we investigated the relationship between social network centrality and an estimate of gastrointestinal helminth infection intensity in a complete group of Japanese macaques (Macaca fuscata). We then tested the impact of missing parts of the group on this relationship. We aimed to test: (1) whether social network centrality - the number of partners (degree), frequency of interactions (strength) and level of social integration (eigenvector) - was linked to parasite infection intensity; and, (2) to what extent excluding all or portions of individuals within the group from the analyses might influence the observed relationship. We conducted social network analysis on data collected from one complete group of Japanese macaques over two months on Koshima Island, Japan, to relate metrics of network centrality to an index of parasite infection intensity (eggs per gram of feces: EPG). We then ran a series of knock-out simulations to test the effect(s) of accounting only for certain age-sex classes on the observed relationship. General linear mixed models showed that, in the complete network, centrality was positively associated with infection by the examined geohelminths (Oesophagostomum aculeatum, Trichuris trichiura and Strongyloides fuelleborni), but in partial networks with only adult females, only juveniles, or random subsets of the group, the strength of this relationship - albeit still positive - lost statistical significance. Our study indicates that sampling bias can impact the relationship that is observed between social interaction and parasitism. In addition to supporting earlier results linking geohelminths to Japanese macaque social networks, this work introduces important methodological considerations for research into the dynamics of social transmission, with applications to infectious disease epidemiology, population management, and health interventions.