Culture and variation in wild chimpanzee behaviour : a study of three communities in West Africa
The concept of culture has recently been used to explain behavioural variation and trans-generational continuity of behaviour in non-human animals and in chimpanzees in particular. However, few studies in the wild have systematically investigated how the environment and behavioural adaptation might influence behavioural diversity. In this context, one habituated community of wild chimpanzees (Pan troglodytes verus) at Bossou, Guinea, and two neighbouring non-habituated communities in the Nimba Mountains region of Guinea and Cote d'Ivoire were the subject of a detailed study of behavioural variation at the intra- and inter-community level. An ecologically-based approach was adopted to investigate variation in nest building, in the use of the oil-palm tree (Elaeis guineensis), in ant-dipping and in tool-choice and -manufacturing. A significant influence of environmental variables on nesting parameters emerged explaining much of the variation observed between the three sites. However, some differences that arose are more likely to reflect differences in social structure and organisation. The comparative study of the utilisation of the oil-palm tree failed to reveal proximate environmental parameters that might explain significant observed variations in use. These findings raise interesting and important questions pertaining to diffusion of behaviour between neighbouring chimpanzee communities. Dipping for driver ants, Dorylus spp., is often cited as one of the best examples of culture in chimpanzees. A detailed analysis of this behaviour at Bossou suggests that risk exposure affects frequency of performance in the developing chimpanzee and reveals a strong influence of prey characteristics, including aggressiveness and/or gregariousness , on tool length and technique employed. Variations in tool-choice and tool-manufacturing within and between three tool-use behaviours at Bossoui nvolving the use of a stick or a stalk were found to be significantly associated with the nature of the task and its predictability, emphasising the importance of environmental affordance and constraints on these processes. In addition, efficiency in behaviour across another set of three tool-use behaviours was explored focusing chiefly on age-class differences. An analysis of individual and community-level patterns of laterality in hand-use between these three tool-use behaviours is also provided. The data supply some evidence to support the selective advantages of lateralization in hand-use with respect to behavioural efficiency. The findings also suggest that haptic tasks have played an important evolutionary role in driving population-level handedness, and reveal that although complex tool-uses exhibited high levels of lateralization, these failed to show task specialisation across individuals. Finally, this thesis presents a comprehensive review analysis of individual and community-wide variation across a range of behaviours observed in chimpanzees and identifies paths and hypotheses that warrant further exploration and testing with the aim to gain further insight into cultural processes in nonhuman animals.