Chimpanzee culture in Cantanhez National Park, Guinea-Bissau

The existence of non-human animal (hereafter animal) culture, i.e., behaviours that are group-typical and shared by members of a community through social learning, is now generally accepted. Its presence has been identified in many vertebrate, and even invertebrate, species. Much like in humans, culture is present in the most diverse aspects of an animal’s life, from complex material culture, communication, and social behaviours, to foraging, travel, and migratory routes. Importantly, culture can be a source of adaptive behaviour whereby individuals can more readily discover the solution to a problem if they attend to or copy the behaviour of other individuals facing the same problem, allowing individuals to better exploit their natural and social environment. Of all animal species, chimpanzees (Pan troglodytes) have the largest known cultural repertoire. However, despite several long-term field studies, large gaps remain in our knowledge of the behavioural repertoire of and behavioural variation across the majority of Africa’s chimpanzees. Furthermore, few studies have compared the behaviour of neighbouring chimpanzee communities, despite such comparisons promising to provide the strongest evidence for culture, and few have studied communities inhabiting anthropogenic landscapes, although their culture is in the most imminent danger of disappearing.
The aim of this thesis was to study behavioural variation across four unhabituated neighbouring chimpanzee (Pan troglodytes verus) communities, inhabiting an agroforest habitat matrix in Cantanhez National Park (CNP), Guinea-Bissau. As these critically endangered chimpanzees regularly encounter local people and a loss of fear of humans might drive aggressive interactions, habituation was never a possibility. Therefore, a combination of direct opportunist observations, but mostly indirect methods of data collection (e.g., camera traps, abandoned tools, nests) were employed. Additionally, a combination of data analysis methodologies – automated behavioural annotation, primate archaeology techniques, and stable isotope analysis – were used to tackle the large data set collected, which included 4197 chimpanzee videos, 1747 indirect chimpanzee traces, 125 chimpanzee hair samples, and 390 plant samples.
In Chapter 2 I compile a list of 18 putative cultural behaviours for CNP’s chimpanzees, some of which had never been described for Guinea-Bissau, or even the rest of tropical Africa, and describe evidence of inter-community variation that spans tool use, communication, and social behaviour. In Chapter 3 I focus on a subset of these cultural behaviours – honey dipping – and describe inter-community variation as well as variation in tools used to collect the honey from different insect species. Employing primate archaeological techniques, I assign putative functions to the collected tools and suggest that different tools are used as part of a tool set. In Chapter 4, with the aid of an automated, machine learning based drumming annotation software, I examine a chimpanzee ‘universal’ – buttress drumming – and identify inter-community variation in drumming duration. Through exploring the contexts in which drumming occurs, I further suggest that the duration of a drumming bout might be part of community-specific signalling in particular contexts, such as travel. Finally, in Chapter 5 I use stable isotope analysis and find significant inter-community variation in the diets of these neighbouring chimpanzees, that point towards previously unknown differences in feeding behaviour.
Overall, this thesis presents the first long-term study focussed on chimpanzee behavioural variation in CNP, highlighting the importance and feasibility of simultaneously studying multiple neighbouring communities, without the need for habituation. Technological advances have not only changed the way we collect data but also the type and amount of data we can collect and analyse, allowing us to closely examine many aspects of an animal’s life. Finally, this study underlines how different communities facing similar environmental pressures can adopt different adaptations, even at a local scale. Given the rate of habitat destruction and climate change that wild species are facing, there has never been a more relevant time to study how different communities behave and adapt to life in the Anthropocene.

Keywords: animal culture
behvioural variation
chimpanzees
animal behaviour
chimpanzee culture
Advisor: Biro, D
Kimberley, H