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Baboon portraits

Get close-up and personal with some of our baboon ladies here

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Ilana Zucker-Scharff

Ilana is currently investigating seasonal and individual variation in energy metabolism in female chacma baboons for her senior thesis at Barnard College, Columbia University. She is quantifying urinary C-peptides, an indicator if insulin production, to assess whether females encounter variable levels of energetic stress, and how that variation may relate to feeding ecology and seasonality, as well as reproduction.

  • Nadya Ali

Nadya Ali

Nadya worked in my lab at Barnard College, Columbia University, in 2012/2013. She studied how guenon grooming networks changed with reproductive state and seasonal variation in food availability and competition. Among the findings was evidence for decreased clustering of social interactions during periods of high competition over food, indicating that networks between close social partners disintegrated to some extent during those times. Read more

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Kiio Kithome

Kiio conducted his Master’s thesis work on characterizing the intestinal parasite infections of blue and Sykes’ monkeys in Kenya. Among the findings was a rank relationship between dominance status and both, infection risk and infection intensity, with several common nematode taxa. He is currently preparing for further graduate studies assessing the spatial correlates of parasite infections and ecological factors determining exposure among female chacma baboons, as part of the Tokai Baboon Research Project in South Africa.

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Social bonding and health in chacma baboons

The Tokai Baboon Sociality Project

In many primate societies, individuals form strong, long-lasting social bonds. It is now known that these bonds can be adaptive, for example by increasing longevity, offspring survival, and, ultimately, reproductive success. What is still poorly understood are the mechanisms by which social bonds achieve their effects. One possibility is that because of their known function in helping individuals cope with stressors, social bonds mitigate negative effects of chronic stress on health and reproduction. But whether – and how – social stress in wild social groups of primates influences female reproduction is also poorly understood.

The Tokai Baboon Sociality Project addresses these gaps in our knowledge by testing three potential pathways that could connect variation in social bonds with measures of health and reproductive function: 1) the lack of strong social bonds leads to elevated stress hormone levels that in turn mediate increased susceptibility to intestinal parasite infections, with potential effects on energy availability; 2) social stress influences reproductive physiology directly; 3) social bonds mediate success in feeding competition; and 4) social bonds (particularly with males) reduce exposure to aggression and infanticide risk.

Data for this project were collected from two troops of chacma baboons (Papio ursinus) on the Cape Peninsula of South Africa. Methods included (1) behavioral observations to document sources of stress and social bonds; (2) measurement of stress and reproductive hormone levels in fecal samples; (3) examination of intestinal parasites from fecal samples; (4) measurement of energy balance via urinary C-peptide, a byproduct of insulin production; and (5) a novel field experiment in which intestinal parasites are eliminated from a random selection of females to assess, for the first time in a wild primate, the factors associated with the timing and intensity of re-infection.

Analyses are currently underway and will continue into 2016. Ultimately, this project will generate new insights into the mechanisms linking social behavior, stress physiology, health, and reproduction and help elucidate the function of social bonds in primate societies.


Glucocorticoids or GCs (stress hormones) such as cortisol are the primary mediators of physiological responses to physical or psychological perturbations from homeostasis in all vertebrates. During acute stress responses, these hormones optimize the availability of energy needed to cope with a stressor and activate important aspects of the immune system. When exposure to a stressor exceeds the coping capacity of the organism, however, the beneficial actions of stress hormones turn into maladaptive responses that contribute to the depletion of bodily resources, increase disease risk and progression, and may even lead to death.

Non-invasive techniques to quantify GC metabolites in urine or feces have resulted in a growing number of studies that use GCs to assess “costly” aspects of behavior and life history in wild vertebrates. The interpretation of naturally occurring hormonal variation is rendered difficult, however, by the dearth of studies documenting effects of variable stress levels on reproduction in non-human primates and humans. Much of what we know about the health effects of social stress comes from studies conducted on captive non-human primates, or from modern human societies where natural social coping mechanisms may be impaired and individuals subject to high levels of life and work stress. Given its partly adaptive function, some observed variation in stress levels is likely tied to fitness-maximizing strategies; this may explain why a recent review of vertebrate studies found conflicting evidence for a relationship between GCs and indicators of fitness.

To interpret stress responses in wild primates using non-invasive measures and to understand their evolutionary significance, it is necessary to (a) study tangible fitness correlates and how they are modulated by, or modulate, GCs, (b) collect longitudinal data on individual stress responses and measures of reproductive function, (c) study free-ranging populations, because artificially high levels of psychological stress that often occur in captivity are unlikely to reflect daily life experiences in an evolutionary context, and (d) disentangle the influence of social stressors from that of energetic stressors.

The Tokai Baboon Project tries to meet these requirements by (1) studying social groups that are free-ranging but relatively well buffered against energetic stressors due to partial reliance on anthropogenic food sources; (2) collecting a large number of biological samples to arrive at representative estimates of hormone metabolites; (3) evaluating multiple potential stressors and controlling for confounds of stress responses using modern statistical tools, and (4) quantifying the association of GC variation with two potential fitness correlates: reproductive function and the number and relative intensity of gastro-intestinal (GIT) parasite infections. GIT parasite infections are a potential correlate of fitness because they can have effects on host nutrition, immunology, and reproduction, and are known to influence health and morbidity in humans.

Structure and function of social networks

Picture2Primate social groups consist of a network of interactions that build upon dyadic relationships of their members. While traditionally these pairwise interactions have been the focus of much research on the structure and function of social behavior, characterizing the complex social experiences of individuals, or the pattern of interactions in an entire group, is not easily achieved through such measures. I am interested in exploring the use of Social Network Analysis (SNA) – a formalized set of tools for studying the connectivity among members of social units and their complex multidimensional structure – for understanding the adaptive value of behavioral strategies in primate groups.

Based on existing evidence from humans and some non-human primates, social integration can be an important factor influencing health and reproduction. Using SNA, it is possible to take into account not just the number of partners, but also the distribution of interactions and the relative “importance” of each partner, i.e. their respective positions and influence.

There are many open questions about what aspects of social structure are most relevant to individuals and under what social and ecological conditions, or what mechanisms are responsible for the evolution of these structures and their consequences on individual fitness.

I address this topic with data on three different primate taxa: forest guenons (blue monkeys & Sykes’ monkeys), chacma baboons, and chimpanzees. A comparative approach across taxa may ultimately reveal new insights into the evolution of primate social structure that go beyond what we can learn from studying dyadic interactions.

Larissa Swedell, Queens College, CUNY

cuny-queens-collegeLarissa and I co-manage the Tokai Baboon Project in Cape Town, South Africa, investigating the effect of social stress on health and reproduction in female chacma baboons. Follow the main menu to find out more information on this project.

Steven L. Monfort, Conservation Biology Institute

Smithsonian_logo_color.svgAs the director of the Conservation Biology Institute of the National Zoo and a long-time endocrinologist who helped pioneer non-invasive assessments of fecal hormone metabolites several decades ago, Steve provides logistical support for lab analyses of stress and reproductive hormones, acts as an adviser, and has provided financial support in previous work on guenon behavioral ecology and stress physiology.

Chris Appleton & Colleen Archer, University of KwaZulu Natal, South Africa

logo2rgbChris and Colleen are both experienced parasitologists who are helping with the analyses of baboon fecal samples from the Tokai Baboon Project, which will help us determine possible consequences of socially mediated stress on the susceptibility to parasite infections.

Gilda Morelli & Paula Ivey Henry

1024px-Boston_College_Seal.svg Harvard_shield-Public_HealthTogether with Gilda and Paula, I explore the development of infant social networks in Efe hunter-gatherers in the Democratic Republic of Congo. This research is based on data collected by Paula in the late 80s, and consists of unprecedented detailed behavioral observations on a set of infants and toddlers in their first years of life, which provides many opportunities for continuous analyses.