Social behavior, adaptive responses, and developmental constraints
There is a large body of research on the connections between early life conditions (e.g. environmental factors like resource abundance, but also social factors such as caregiving environments) and later-life outcomes . Are the downstream outcomes adaptive responses that maximize lifetime fitness (e.g. the predictive adaptive response hypothesis), or are they simply the result of constraints imposed by environmental realities during development (e.g. the developmental constraints hypothesis)?
Prior research in this area has focused heavily on epigenetic and physiological mechanisms, and has not yet leveraged the fundamental role that behavior generally, and social behavior specifically, may play. This project is a collaboration with Dr. Beth Archie, and uses data from the Amboseli Baboon Research Project. The baboons’ high environmental variability, male dispersal, and strong female dominance hierarchies make them an ideal system to study how social variables interact with ecological ones, and how the relationship between early life experiences and later outcomes is mediated by social bonds and intraspecific competition.
Reproductive strategies and steroid hormones in non-seasonal breeders
There is an extensive body of literature on the endocrine system switches that occur as seasonally-breeding organisms shift from mating to parenting effort and back again (aka the Challenge Hypothesis). The Challenge Hypothesis is a powerful framework for understanding hormonal mechanisms and reproductive effort in some species, but its predictive power is limited in non-seasonal breeders, and it treats “mating effort” and “parenting effort” as monoliths rather than the complex suite of behaviors each actually represents. In species such as mountain gorillas and humans, non-seasonal breeding is combined with extended offspring development, during which males offer both direct and indirect care. Organisms like these offer ideal opportunities to understand how hormonal mediators work when competing needs must be balanced.
Using longitudinal behavioral and hormonal data from both gorillas and humans, we are exploring how steroid hormones are related to intra- and inter-individual variation in male reproductive strategies, including caretaking. Across the two species, this research addresses hypotheses about (for example) the effect alloparental care has on males’ testosterone profiles, and how testosterone profiles respond to the changes in caretaking behavior that occur as offspring age and become less reliant upon intensive care.
Male development and life history strategies
Male mountain gorillas go through a period of uncertainty after they've become reproductively mature, but have not yet fully developed the secondary sexual characteristics of a fully adult silverback (e.g., large body size, sagittal crest, silver hair on their back). They face critical life history decisions, such as whether to remain in their natal group or disperse, or compete immediately versus wait for later mating opportunities. These decisions may have effects on male development and physiology, including the speed at which they acquire secondary sexual characteristics. We know a phenomenon called "bimaturism," (where males can employ different reproductive strategies by maturing at different times) happens in other primates such as orangutans, but does it happen in gorillas as well? This project is led by graduate student Ella Brown.
High elevation adaptation and climate change
Non-human primates are losing their habitats at a faster rate than ever before, and with the looming threat of climate change, this is unlikely to resolve itself. Primates living in extreme and variable environments will likely be the most negatively impacted. The Virunga mountain gorilla population living in Volcanoes National Park has adapted to live in cold and wet conditions at a high elevation. We are specifically interested in questions such as, how does the Virunga gorilla population behaviorally and physiologically adapt to this extreme environment? how do their environmental conditions and stressors vary across the different microclimates they use? how will this population be affected by climate change? It is unclear if the current adaptations used by Virunga gorillas will be enough to survive the predicted warming climate of this region. Therefore, It is important to measure their physiological and behavioral responses as the climate continues to warm, This project is led by graduate student McKensey Miller.
Female intrasexual competition
Like most social animals, female mountain gorillas compete over limited resources that improve their chances of survival and reproduction. While physical resources like food are certainly
important, social resources such as friends or allies can also offer benefits. Some female gorillas are known to behave aggressively towards other females when near adult males, who can provide infant care, protection, and potentially help with social integration. Social access to adult males may even be an important factor influencing differences in reproductive outcomes among female gorillas, differences feeding competition currently cannot explain. Yet, we know
remarkably little about the prevalence and potential significance of female-female competition over social resources in gorillas and other social animals. This research behavioral, demographic, and physiological data to investigate three main questions: What are female gorillas competing over? What are the costs of their competition? And finally, what are the benefits? This project is led
by graduate student Dominic Mayo.
Atlanta, Georgia & Musanze, Rwanda
Dr. Tara Stoinski, Dr. Winnie Eckardt, Dr. Shannon McFarlin, Dr. Robin Morrison, Ms. Rose Umuhoza
Northwestern University
University of Notre Dame, Duke University, Max Planck Institute for Evolutionary Anthropology
