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Research at Cayo Santiago

Image credit: Raisa Hernández

A longitudinal analysis on the variance of extra-group paternities in rhesus macaques
Angelina Ruiz-Lambides, M.A., PhDc, Caribbean Primate Research Center, UPR

Dr. Anja Widigg, University of Leipzig and Max-Planck Institute for Evolutionary Anthropology, Leipzig

Alternative mating strategies, such as extra-group paternities (EGP), may be driven by the divergence of reproductive interests between males and females. EGPs may counteract negative fitness consequences, contribute to genetic variance or change group stability. They have broadly been described in several species of non-human primates, wherein genetic data of a few birth cohorts of a given social group revealed that a proportion of offspring are typically sired by males not resident to the social group at the time of offspring conception. Whereas much has been discussed about the occurrence of surreptitious matings, minimal work has been done to analyze factors leading to EGPs in non-human primates. My study will comprise nine years of demographic, dominance and genetic data of all groups of the rhesus macaque population of Cayo Santiago. We will investigate EGPs from different perspectives including from the social group level, male and female individual perspective.


Heterogeneity of life courses

Predicting ecological and evolutionary dynamics requires an understanding of the diversity of life courses among individuals, since life courses shape demography, which in turn drives evolution. Heterogeneity among individuals influences the speed of adaptive and neutral evolutionary processes, but it is less clear how biotic and abiotic environmental fluctuations influence variability among individuals. Such variability is reflected in individual life courses, defined as the sequence of stages experienced during an individual’s life. Identifying the sources of variation in life courses remains a fundamental task to address in order to understand the meaning and significance of phenotypic variation within populations. A multi-stage model using a first-order Markov process describing reproductive dynamics, as well as estimates of population entropy are being used.


Understanding of Animate and Inanimate Objects in Rhesus Macaques
Dr. Laurie Santos, Yale University

The aim of this study is to explore what rhesus macaques understand about the physical and social world. This project first examines whether rhesus monkeys reason about agents in the same way as humans do – by considering their intentions, beliefs, and desires. These questions are to significant importance in the field of developmental psychology and comparative cognition – the question of whether non-human primates can reason about objects and agents has been one of the longest-standing questions in the field of primate cognition. In addition, learning more about how monkeys reason about agents will provide a potential animal model of human disorders to agency understanding (e.g. autism).


Genetics of Social Decision Making in Rhesus Macaques
Dr. Michel Platt, University of Pennsylvania

The current investigation seeks to understand the neural mechanisms responsible for making decisions, approached with a panoply of behavioral, physiological and genetic techniques. His current research aims to examine genetic and endocrinological factors underlying individual variation in social behaviors and the processing of social information in rhesus macaques. This research is part of a larger effort to develop an animal model of complex social behavior which can be used as a model to understand human behavior, including pathologies such as autism.


Economic and social decision-making in rhesus monkeys
Dr. Alexandra Rosati, Harvard University

This project will examine how rhesus macaques make decisions in order to understand the evolution of human-like economic behavior and self-control. Decision-making pervades human life, from assessing whether to save or invest money, to choosing whether to give into temptation and eat a slice of cake. These types of decisions often have parallels with wild behaviors, as foraging animals must assign value to different possible options, make trade-offs between costs and benefits, and deal with conspecifics who are trying to solve the same problems. As these complex skills often show significant changes across the lifespan in humans, we will therefore examine monkey decision-making across early development, adulthood, and aging in order to understand the ontogenetic trajectories of decision-making across species.


Mechanisms of Paternal Kin Discrimination
Dr. Anja Widdig, Max-Planck Institute for Evolutionary Anthropology and University of Leipzig

To date, there is limited information on the impact of paternal relatedness upon the evolution of social behavior, and of its underlying mechanisms. Therefore the aim of this study is to investigate the mechanisms and cues rhesus macaques use to identify their paternal kin. To do so we combine long-term behavioral, demographic and genetic data to distinguish between the two most likely mechanisms: familiarity and phenotype matching. Furthermore, we investigate potential cues used such as visual, odor, and acoustics via different experimental approaches conducted in the field.


The Relationship Between Social Network Position, Personality Traits, and Stress Buffering Hypothesis in Juvenile Rhesus Macaques
Katharine Burke, Ph.Dc, SUNY, University of Buffalo

The aim of the doctoral dissertation is to examine the extent to which aspects of the stress-buffering hypothesis may apply to juvenile monkeys, by examining whether these links are also present in juvenile free-ranging rhesus monkeys (Macaca mulatta) on Cayo Santiago. The focus is to study relationships between individual basal stress hormone levels, social network positions related to direct and indirect connectedness, and personality traits among juveniles as well as the relationship between the basal stress hormone levels and personality traits of an individual’s close peers.


Sexual Selection and Morphological Traits
Dr. Contance Dubuc, University of Cambridge, UK

Sexual selection selects for male traits that increase the number of offspring produced. In mammals, sexual selection is typically expected to leads to large, weaponized males with horns, antlers, and elongated canines. Indeed, because these traits help males fighting off and intimidate other males, as well as mate-guard females, males who carry them enjoy a high reproductive success. Interestingly, however, there is increasing evidence that there are alternative routes to success in mammals; Indeed, although smaller-sized less-armored individuals can only reproduce using less efficient alternative strategies, they are less likely to die at young age through deadly fights, such that they breed over a longer period of time. I am interested in examining the role sexual selection play in shaping male morphological traits and how it relates to different behavioral strategies and life history trajectories in the Cayo Santiago free-ranging rhesus macaque population, through observation of live subjects and examinations of skeletal remains collected over decades.


Grooming exchange: Cooperation and supply and demand among free-ranging rhesus monkeys (Macaca mulatta) on Cayo Santiago
Erica Dunayer, Ph.D candidate, University at Buffalo, SUNY

Dr. Carol Berman, University at Buffalo, SUNY

This doctoral dissertation will investigate cooperative exchanges in order to test predictions from several competing evolutionary hypotheses about cooperation. Specifically, the project will examine how well reciprocal grooming exchanges resemble those predicted by several competing theoretical hypotheses (kin selection, reciprocal altruism, biological markets theory, and social bond investment), in one comprehensive and integrated analysis. Additionally, there will be a more detailed investigation of biological markets theory. By focusing on exchanges of grooming for mates or infant handling, this study will also test a key prediction that exchanges conform to supply and demand relationships. The extent to which apparent supply and demand relationships may be artifacts of, or mediated by, stress responses will be examined behaviorally and physiologically.


The biological basis of social relationships and cooperation 
Dr. Lauren Brent, University of Exeter
The aim of this research is to determine why social relationships are formed and how they are maintained. Within groups, individuals differ in their tendencies to interact with others and in how deeply embedded they are in their social networks. This research investigates the heritable basis of individual differences in sociality, along with their physiological causes and impacts on health, life-history, and fitness. In addition, this research explores the evolutionary mechanisms that underpin social dynamics and asks how cooperation is maintained in animal societies.

Adult male-immature relationships and stress in immature rhesus macaques (Macaca mulatta)
Kristín Ocasio, Central Washington University
Jessica Mayhew, Central Washington University
In a multi-male and multi-female primate society the paternity uncertainty is high. However, in species with high paternity uncertainty, it has been found that father-offspring affiliations are more frequent than affiliations between unrelated adult males and immature individuals during the first 2 years of age. More research is needed on adult male-immature relationships; for example, how maternal care style may affect these relationships. This study is aimed at investigating the potential effects of male care in the frequency of stress behavior indicators (e.g. yawn) on immatures rhesus macaques (Macaca mulatta). It is expected that having the support and protection of an adult male may decrease the stress associated with social interactions, therefore showing less stress behavior indicators.