Though uncommon, adoption of orphaned infants has been observed in both wild and captive non-human primates. In two groups of wild bonnet macaques (Macaca radiata), we observed five instances of infants being cared for after they lost their mothers at a pre-weaning age (< 6 months). Orphaned infants had one or more caregivers (juvenile, subadult, and adult female or male) involved in carrying, grooming, hugging, and protecting them. Adoption did not appear to be related to the age/sex class of the infant, or directly to the mother's rank. Although the dominance rank of the mother of an orphaned infant did not have a direct effect on orphan survivorship, it determined the number of caregivers available to the orphaned infant, and infant survivorship was positively related to the number of caregivers of the orphaned infant. Thus, survivorship was likely a function of the mother's sociality. Two other infants born to high-ranking mothers were also adopted by more individuals and survived longer than the infants of low-ranking mothers.

Pandemics caused by pathogens that originate in wildlife highlight the importance of understanding the behavioral ecology of disease outbreaks at human-wildlife interfaces. Specifically, the relative effects of human-wildlife and wildlife-wildlife interactions on disease outbreaks among wildlife populations in urban and peri-urban environments remain unclear. We used social network analysis and epidemiological Susceptible-Infected-Recovered models to simulate zooanthroponotic outbreaks, through wild animals' joint propensities to co-interact with humans, and their social grooming of conspecifics. On 10 groups of macaques (Macaca spp.) in peri-urban environments in Asia, we collected behavioral data using event sampling of human-macaque interactions within the same time and space, and focal sampling of macaques' social interactions with conspecifics and overall anthropogenic exposure. Model-predicted outbreak sizes were related to structural features of macaques' networks. For all three species, and for both anthropogenic (co-interactions) and social (grooming) contexts, outbreak sizes were positively correlated to the network centrality of first-infected macaques. Across host species and contexts, the above effects were stronger through macaques' human co-interaction networks than through their grooming networks, particularly for rhesus and bonnet macaques. Long-tailed macaques appeared to show intraspecific variation in these effects. Our findings suggest that among wildlife in anthropogenically-impacted environments, the structure of their aggregations around anthropogenic factors makes them more vulnerable to zooanthroponotic outbreaks than their social structure. The global features of these networks that influence disease outbreaks, and their underlying socio-ecological covariates, need further investigation. Animals that consistently interact with both humans and their conspecifics are important targets for disease control.

Time is a valuable but limited resource, and animals' survival depends on their ability to carefully manage the amount of time they allocate to each daily activity. While existing research has examined the ecological factors affecting animals' activity budgets, the impact of anthropogenic factors on urban-dwelling animals' time budgets remains understudied. Here we collected data through focal animal sampling from three groups of rhesus macaques in Northern India to examine whether interactions with humans decrease macaques' resting and social time (time constraints hypothesis), or whether, by contrast, foraging on anthropogenic food, that is potentially high in calories, leads macaques to spend more time resting and in social interactions (free time hypothesis). We found that macaques who interacted more frequently with people spent significantly less time resting and grooming, supporting the time constraints hypothesis. We argue that these time constraints are likely caused by the unpredictability of human behaviour.

Humans and their associated anthropogenic factors may strongly affect the demographics, activity and fragmentation of wild animal populations. Yet, the degree and nature of such impact on indicators of animals’ social relationships remain largely under-investigated, despite the well-documented importance of strong social ties for an individual's health and fitness. Here, we examined whether interactions with humans may affect core aspects of social life in a primate species, by constraining the time available for individuals to engage in social interactions. Specifically, we predicted that individuals who spend more time monitoring or interacting with humans would reduce their time socializing with conspecifics (i.e. the time constraints hypothesis). Alternatively, human presence may result in increased levels of stress, leading to an increase in social behaviours that serve as a coping mechanism (i.e. the social stress hypothesis). We collected data between September 2016 and September 2017 on four groups of longtailed macaques, Macaca fascicularis, in Malaysia at two sites with differing levels of human impact. In support of the time constraints hypothesis, we found that at the site with moderate human impact, monkeys who monitored human activity more frequently engaged less often in grooming. In contrast, at the site with high human impact, we found evidence supporting the social stress hypothesis, as indicators of stress were positively associated with social interactions, although we could not link them to the presence of humans. Our results suggest that the nature of human impact on macaques’ social behaviour is dependent upon the intensity of human activity and interaction with the macaques. These findings therefore provide insights into how humans may influence individual fitness and group social structure in animals living in an anthropogenic environment. More broadly, our results may lead to a better understanding of animal behaviour in anthropogenic environments, implementing conservation and population management strategies and mitigating human–wildlife conflict.

Despite increasing conflict at human-wildlife interfaces, there exists little research on how the attributes and behavior of individual wild animals may influence human-wildlife interactions. Adopting a comparative approach, we examined the impact of animals' life-history and social attributes on interactions between humans and (peri)urban macaques in Asia. For 10 groups of rhesus, long-tailed, and bonnet macaques, we collected social behavior, spatial data, and human-interaction data for 11-20 months on pre-identified individuals. Mixed-model analysis revealed that, across all species, males and spatially peripheral individuals interacted with humans the most, and that high-ranking individuals initiated more interactions with humans than low-rankers. Among bonnet macaques, but not rhesus or long-tailed macaques, individuals who were more well-connected in their grooming network interacted more frequently with humans than less well-connected individuals. From an evolutionary perspective, our results suggest that individuals incurring lower costs related to their life-history (males) and resource-access (high rank; strong social connections within a socially tolerant macaque species), but also higher costs on account of compromising the advantages of being in the core of their group (spatial periphery), are the most likely to take risks by interacting with humans in anthropogenic environments. From a conservation perspective, evaluating individual behavior will better inform efforts to minimize conflict-related costs and zoonotic-risk.