Twenty years with bonnet macaques

Long-term study on the demography and social evolution in wild bonnet macaques

Distribution, morphology, behavioural ecology

The bonnet macaque, a ubiquitous but endemic primate of peninsular India, has been celebrated through art, sculpture and literature as an integral part of southern Indian culture for almost over two thousand years. And yet we know so little of this species, considered one of our most important agricultural pests. The bonnet macaque is believed to consist of two subspecies with subtle morphological differences, with the southern subspecies restricted to southeastern India. Over the last year, we have examined the morphology, demography and life history strategies of identified individuals in selected troops of the two subspecies in two protected areas – Bandipur National Park and Kalakad-Mundanthurai Tiger Reserve – within their respective distributions. This investigation, the fieldwork for which was completed in 2011, thus aims to confirm the biological legitimacy of the two subspecies using several alternative empirical field and laboratory approaches, including geographical distribution, morphometric analysis and population genetic differentiation. The laboratory component of the analysis has also been finished. We propose to integrate all our findings and publish the complete results of the study in the coming year.

Demography, ecology and social evolution

We have also been continuing a long-term field project, begun in 2000 and proposed to continue for twenty years, investigating the demographic structure, population dynamics and socioecology of a population of wild bonnet macaques in the Bandipur National Park – Mudumalai Wildlife Sanctuary complex in the states of Karnataka and Tamil Nadu. During the last year, we have continued our demographic monitoring of twenty-two troops of the species and quantitative observations on the socioecology of five of these groups. During this work, we have been able to document the influence of the tourist traffic through these sanctuaries on the evolution of a new unimale form of social organisation in this species, characterised by certain unique demographic and behavioural features. Our studies on the socioecology of selected multi male and unimale troops in this population have allowed us to evaluate the ecological and anthropogenic factors that may have influenced the trajectories of social change in this population.

Social cognition, communication and culture

One of our long-term interests has been to investigate the social cognitive abilities of wild bonnet macaques, particularly from the perspective of both distributed and/ or embodied cognition as well as individual internal processes such as theory of mind. Our earlier studies had focused on specific behavioural processes including the acquisition of social knowledge and tactical deception in this species. Over the last year, we have been continuing our exploration of these processes and their interactions in wild bonnet macaques, drawing upon inter-disciplinary approaches such as observational studies of behaviour, philosophical analyses and mathematical modelling. We have also continued to document behavioural transmission in this macaque and are currently investigating the cognitive processes underlying tactical deception in wild groups of this species.

Temperament and personality in wild bonnet macaque

Personality, from an evolutionary perspective, represents a meta-category of the output of a suite of species-typical, relatively domain-specific, evolved psychological mechanisms designed possibly in response to the social adaptive problems recurrently faced by our primate ancestors. Early last year, we initiated a study on the evolutionary reconceptualisation of the development, structure, and processes of human personality through a closer understanding of the nature of temperament/personality in nonhuman primates that live in complex social groups, often in changing environments. We are currently in the process of devising novel methodologies that could be employed to not only define but to gain deeper insights into several issues of personality in a nonhuman primate species, typically characterised by remarkable variation in individual life-history strategies. These include, but are not restricted to, consistency/variability in personality traits, individual differences against the background of a ubiquitous species-typical nature, sex differences and similarities, age-graded and developmentally contingent personality phenomena, and the contextual determinants of personality.

Social network analysis of bonnet societies

Our research on primate societies has so far implicitly assumed that social complexity arises due to cognitively sophisticated decision-making processes exercised by each individual on the basis of individually acquired and processed information. Group- level dynamics of complex primate societies could, however, also be explained by more parsimonious, non-cognitive alternative hypotheses arising from general individual-based rules, as predicted by principles of self-organisation and chaos. In 2010, we initiated an investigation into appropriate agent-based models that could account for several emergent properties of the bonnet macaque social networks that we have earlier observed. We are interested in the role played by interactions between general rule-based behaviours and individual-specific cognitive behaviours in the emergence of social networks such as those of cercopithecine primates, which perhaps represent an intermediate stage between the simpler prosimian groups and the much more complex human societies.