In many primate societies, including humans, individuals form strong, long-lasting social bonds which 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, daily-life social stress influences female reproduction in primate societies also is poorly understood. This project will address both of the above gaps in our knowledge by examining the pathways connecting variation in social bonds with measures of health and reproduction. It will assess whether stress hormones mediate the susceptibility to intestinal parasite infections; examine the relationship between social stress and reproductive physiology; and evaluate whether social bonds mediate success in feeding competition, and hence, energy available for reproduction. Data for this project will be collected from three troops of chacma baboons (Papio ursinus) in the Cape Peninsula of South Africa.
The project's multifaceted data will include behavioral observations to document sources of stress and social bonds; measurement of stress and reproductive hormones, as well as intestinal parasite loads, via non-invasively collected fecal samples; and collection of urinary C-peptide (a byproduct of insulin production) to measure energy balance. Additionally, a novel field experiment will be conducted 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. Utilizing this comprehensive approach, the research 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.
Because non-human primates such as baboons share many traits with humans and are useful in studying aspects of human biology, this project will improve understanding of the benefits of sociality during human evolution and carry clinical implications by elucidating the role of social stress as a risk factor for parasite infections. The project will strengthen institutional ties between the U.S. and South Africa, train students underrepresented in science, and provide valuable data and educational resources to aid in management and conservation of primates.
