Abstract
The hominin lineage faced substantial disparities in selective environments over evolutionary time, driving the development of flexible mechanisms designed to cope with periodically stressful conditions. Today, physiological and behavioural flexibility may be a key tool in the adaptive repertoire of wild nonhuman primates facing similar environmental variability due to anthropogenic activities. However, given the rapid pace of contemporary global change, our empirical understanding of the extent to which such flexibility facilitates survival remains limited. Virunga mountain gorillas (Gorilla beringei beringei) provide an ideal system for addressing this research gap. They are vulnerable to entrapment in snares set by people hunting other species for subsistence and are exposed to greater rates of intergroup encounters as their population recovers with the borders of a protected area. Both intergroup and snare encounters pose a considerable risk to mountain gorillas, and there are concerns regarding their rising prevalence. Therefore, we investigated the behavioural and physiological correlates of these social and anthropogenic stressors. We combined longitudinal data collected by the Dian Fossey Gorilla Fund between 2003-2024 with additional data collected between 2023-2024 from eight mountain gorilla groups in Volcanoes National Park, Rwanda. We conducted GPS and instantaneous scan sampling to record ranging patterns, activity budgets, and social dynamics. We also collected faecal samples and assayed faecal glucocorticoid metabolite (fGCM) concentrations to quantify physiological stress. Using geospatial and statistical analyses, we then tested how these behavioural and physiological metrics changed following intergroup and snare encounters compared to baseline. We found that gorillas significantly altered their movement and activity patterns in response to both stressors: they moved more, travelled further, and shifted their ranges away from encounters sites (i.e., reduced site fidelity). They also revisited snare encounter sites less frequently following encounters compared to their previous use of those areas. Together, these results indicate that gorillas actively avoid neighbouring gorilla groups and areas where snares are likely to occur, presumably to mitigate the associated costs. We found limited evidence for social buffering as we did not detect any pre-to-post encounter changes in dyadic affiliative social behaviours. However, we did find that intragroup cohesion increased following exposure to snares and other groups, which, in addition to buffering, may function to enhance cooperation and protection against external threats. fGCMs also increased following both stressors, indicating that the physiological stress response is activated to rapidly mobilise the energy needed to avoid or compete with other groups, move away from areas with snares, or to enhance vigilance and cohesion. This dissertation provides a multidimensional perspective on physiological and behavioural responses of mountain gorillas to anthropogenic and social challenges, offering insights into their adaptive capacity and the role flexibility might play in their survival. However, the potential effects of these stressors, including energetic and fitness costs, remain to be studied. More broadly, these findings shed light on the evolutionary trajectories that shaped the high degree of flexibility within humans and nonhuman primates, and advance our understanding of the coevolutionary relationship between stressors and sociality. Finally, this research has significant practical implications for the conservation of mountain gorillas and other wild animal populations in protected areas, in addition to the wellbeing of adjacent human communities. Management strategies must demonstrate the same high degree of flexibility as the species we hope to protect; ideally, we must integrate continued wildlife and habitat monitoring with efforts to address the complex and multifaceted underlying needs of neighbouring communities to alleviate illegal resource use in protected areas.
Committee Chair
Krista Milich
Committee Members
Crickette Sanz; Emily Wroblewski; Stacy Rosenbaum; Winnie Eckardt
Degree
Doctor of Philosophy (PhD)
Author's Department
Anthropology
Document Type
Dissertation
Date of Award
4-24-2026
Language
English (en)
DOI
https://doi.org/10.7936/amkg-t683
Author's ORCID
https://orcid.org/0000-0002-3971-3759
Recommended Citation
Wiseman-Jones, Lauren Marilyn, "The Physiological and Behavioural Responses of Mountain Gorillas (Gorilla beringei beringei) to Social and Anthropogenic Stressors" (2026). Arts & Sciences Graduate Student Theses and Dissertations. 3768.
The definitive version is available at https://doi.org/10.7936/amkg-t683