Mannion, K. R. | bioRxiv Science

bioRxiv2026

Wild chimpanzees in Bugoma Forest, Uganda follow the Ugandan feeding ecology etiquette but exhibit cultural singularities: a case for the cultural junction hypothesis

Chimpanzees, amongst other primates, are characterized by the large variability of habitats they can be found in as well as a large behavioral, sometimes cultural diversity. Such observations have launched a decades-long debate on the roots of behavioral diversity, stressing the need to document this behavioral variability in context, such as by connecting closely related populations through localized analyses. This study presents the first comprehensive description of feeding ecology from the Mwera South chimpanzee (Pan troglodytes schweinfurthii) community in the Bugoma Central Forest Reserve, in Uganda, establishing a valuable baseline for this previously unstudied population and providing a comparative perspective on the populations of Western Uganda and Eastern Democratic Republic of Congo. By employing multiple methodological approaches, including direct observation and fecal analysis, we describe dietary composition, seasonal patterns, and environmental influences on feeding behavior. Characterizing the feeding ecology of this previously unstudied population is critical for examining how ecological factors might influence how feeding patterns evolve depending on resource availability or chimpanzee behavior, in particular by favoring analyses at the regional level. In addition, we can better evaluate to what extent behavioral differences between chimpanzee communities stem from ecological constraints and/or cultural transmission pathways. Our findings suggest that the Bugoma chimpanzees seat at the location of a historic cultural junction, opening a large array of questions about historic movements and cultural diffusion in Eastern chimpanzees.

animal behavior and cognition↗

bioRxiv2025

Variation in cultural attitude, knowledge and individual motivational factors impact engagement and tool use in a field experiment in wild chimpanzees

Cultural traditions shape how animals approach and solve problems. Previously, Ugandan chimpanzees (Pan trogodytes schweinfurthii), have engaged with the honey-trap experiment, an apparatus designed to mimic a beehive and provide ecological opportunities for tool use, relying on their cultural knowledge. Here, we presented chimpanzees from the Mwera South community, a newly habituated community in Bugoma Forest, with variations of the honey-trap experiment and compared their engagement to other Ugandan chimpanzee communities to investigate various aspects of cultural behaviour in animals. First, we wanted to test whether communities varied in cultural attitude towards a given food, and whether this attitude correlated with particular instrumental components of their cultural knowledge. Second, we were interested in analyzing individual variation across individuals within the same culture. Comparing individuals from Bugomas Mwera South (N=15), Budongos Sonso (N=34), and Kibales Kanyawara (N=14) communities, we found that the latter both exhibited higher engagement with the honey-trap, and a dedicated instrumental method, stick use, to obtain the honey. In contrast, Sonso and Mwera South chimpanzees appeared similar in lacking a cultural attitude towards honey, with no attached tool technique overall. Nevertheless, there were also strong inter-individual differences. Notably, some Mwera South chimpanzees displayed undescribed behavioural flexibility, using a range of tool behaviours including both stick and leaf tool use --a pattern never before documented in over a decade of honey-trap experiments. These results demonstrate that cultural attitudes toward resources constitute an additional layer to culture in addition to instrumental knowledge, and that the latter two coexist with individual motivational traits in influencing the realization of cultural behaviour.

animal behavior and cognition↗