Abstract
In northern Congo, sympatric western lowland gorillas (Gorilla gorilla gorilla) and central chimpanzees (Pan troglodytes troglodytes) face many threats, including hunting, human-induced habitat disturbance, and infectious diseases. This research presents three projects that explore factors that can affect the transmission of pathogens and development of disease in western lowland gorillas and central chimpanzees. Information and data were collected at multiple scales and different conservation contexts, from the individual apes, to social dynamics of the groups in which they live, and to the mammalian communities in which they have long coexisted in the Congo Basin of which they are a part. The first chapter, "Comparing the Life History and Demography of Sympatric Western Lowland Gorillas (Gorilla gorilla gorilla) and Central Chimpanzees (Pan troglodytes troglodytes)", details the life history and demography of the habituated western lowland gorillas and central chimpanzees in the Goualougo Triangle and Djéké Triangle in the Republic of Congo. We found that the gorillas and chimpanzees in our study had broadly similar demographic patterns, including life spans, birth rates, infant mortality, and the presence of a significant post-reproductive period. This confirmed the findings of previous research that the fruit-heavy diets of both western lowland gorillas and central chimpanzees lead to similarly slow life histories. Understanding the life history of a species provides insights into the range of effects a pathogen could have on a potential host of that species, and how the presence of that species in a broader community will affect the transmission of pathogens among sympatric species. These findings also contribute to remedying the scarcity of life history data and demographic data from chimpanzees and gorillas in this region which is essential for informing monitoring programs and conservation policy. Given the pristine nature of the protected forest in northern Congo where these habituated great apes live, our results indicate that intact forests, especially in protected areas, are important to the demographic stability of western lowland gorillas and central chimpanzees, and that habitat disturbance could be disruptive to the life histories of great apes living outside of protected areas. In the second chapter, "Comparing Correlates of Clinical Signs of Disease in Sympatric Western Lowland Gorillas and Central Chimpanzees", data from those same habituated gorilla and chimpanzee groups were used to explore how social and environmental factors affect and are affected by respiratory illness, gastrointestinal distress, and lesion outbreaks among the habituated apes. This work built on previous health monitoring of the habituated gorilla groups in the Goualougo Triangle and Djéké Triangle and the empirical social networks studied in these habituated groups. Results indicated that the intersection of demography and environmental factors such as fruit availability, as well as the social interactions of gorillas and chimpanzees, were all predictors of great ape health, with variations between species and clinical sign. By understanding the effects of fruit availability, demography, and sociality on health, we explored how they can provide additional pathways through which habitat disturbance could further exacerbate the prevalence and severity of disease in great apes, and improve our understanding great ape health in the face of global change. The third chapter, "Mammalian Biodiversity Estimates Across an Anthropogenic Disturbance Gradient in Central Africa", uses invertebrate derived environmental DNA to study the mammalian community in which these great apes exist across an anthropogenic disturbance gradient in northern Congo. The relationship between biodiversity and pathogen transmission is well studied and stridently debated, but for many zoonotic and anthropozoonotic pathogens, evidence has emerged that their transmission is negatively correlated with biodiversity, and that anthropogenic disturbance is an important mechanism mediating this relationship. The anthropogenic disturbance gradient studied here seeks to capture a variety of contexts where the connections between humans and wildlife can lead to higher transmission of zoonotic pathogens. Both distance from a village and distance from a road correspond to the level of human pressure and had significant effects on the distribution of mammals found in the areas around Nouabalé-Ndoki National Park. We also found that intact forests were important habitats for many animals in the region, including both western lowland gorillas and central chimpanzees. The results obtained from this environmental DNA survey differed in species composition from our previous work in the region using camera traps to study biodiversity, despite their similar species richnesses, showing the value of complementary methods for assessing biodiversity in the region.
Committee Chair
Crickette Sanz
Committee Members
David Morgan; Elizabeth Quinn; Emily Wroblewski; Livia Patrono
Degree
Doctor of Philosophy (PhD)
Author's Department
Anthropology
Document Type
Dissertation
Date of Award
8-18-2025
Language
English (en)
DOI
https://doi.org/10.7936/mwy8-hz59
Author's ORCID
https://orcid.org/0000-0003-0775-4852
Recommended Citation
McElmurray, Philip, "The Effects of Habitat and Anthropogenic Disturbance on Western Lowland Gorillas (Gorilla gorilla gorilla), Central Chimpanzees (Pan troglodytes troglodytes), and Associated Mammal Community" (2025). Arts & Sciences Theses and Dissertations. 3604.
The definitive version is available at https://doi.org/10.7936/mwy8-hz59