My research program focuses on the physiological and behavioral mediators of fitness in non-human primates, paying particular attention to how early life conditions influence the trajectory of development, resulting in differences in adult survival and reproduction. To address these questions, I collect behavioral, demographic, physiological, and morphometric data on wild primates. I assess physiological markers and morphometrics noninvasively, the former by examining hormones, biomarkers of immunity, and gut microbiota from excretia, and the latter by measuring stature with the use of digital photogrammetry. Such measurements allow me to assess multiple facets of primate development, and allow for the integration of both mechanistic and evolutionary approaches towards understanding how events during infancy and juvenility can have reverberating impacts into adult life. I am currently involved in two large research projects.
- Physiological Signatures of Variable Weaning Strategies in Wild Geladas. This is an NSF (BCS-1723228) and Leakey Foundation funded collaborative project with Noah Snyder-Mackler (University of Washington) and Laurie Reitsema (University of Georgia), focusing the causes and consequences of premature weaning in wild geladas. In humans extreme cases of premature weaning have been linked to numerous deficits in development, including stunted growth and impaired immunity, yet two aspects of this equation are poor understood: (1) From an evolutionary perspective, what are the conditions that cause early withdrawal of maternal investment? Geladas are a perfect model for this question because stressful social conditions (i.e., alpha male takeovers) that are commonly linked to maternal withdrawal occur frequently in this species. These conditions also allow us to ask: (2) What physiological mechanisms mediate the downstream consequences of premature weaning, specifically in relation to impaired immune development? To address these questions, we are using a suite of innovative techniques in digital photogrammetry to examine growth, isotopic and elemental chemistry to characterize the trajectory of weaning, and genomics to sequence the gut microbiome, a system recently linked to the development of the immune system. We anticipate that these approaches will generate a broader understanding of premature weaning and its consequences in a wild primate.
- Maternal programming of the infant gut-brain axis in vervet monkeys. This is a collaborative project involving my graduate student, Lauren Petrullo, Noah Snyder Mackler (University of Washington), and the Wake Forest University Primate Center. Together we are interested in understanding how mothers can “program” developing infant phenotypes via prenatal and postnatal mechanisms. While prenatal programming of infant outcomes through gestational maternal glucocorticoids is now fairly well-established, the mechanisms by which mothers can alter infant development in the postnatal period may be more varied, but less understood. Here we investigate how social stress during the early postnatal period can cause mothers to alter infant growth and immunity via signals such as glucocorticoids, DHEAS, oligosaccharides, and microbiota transmitted through breastmilk. We are currently collecting pilot breastmilk and fecal samples from lactating mothers and their 3-day old infants to (1) validate the measurement of steroid hormones from breastmilk, and (2) characterize the milk microbiome of mothers and the gut microbiome of young infants. In order to compare the effects of postnatal to prenatal stress, we are also validating the measurement of hair cortisol in neonates as a proxy for gestational maternal glucocorticoids. Together, these preparatory steps will allow us to tackle larger questions of maternally-programmed developmental plasticity in nonhuman primates.