Chimpanzee Personality and the Arginine Vasopressin Receptor 1A Genotype

Polymorphisms of the arginine vasopressin receptor 1a (AVPR1a) gene have been linked to various measures related to human social behavior, including sibling conflict and agreeableness. In chimpanzees, AVPR1a polymorphisms have been associated with traits important for social interactions, including sociability, joint attention, dominance, conscientiousness, and hierarchical personality dimensions named low alpha/stability, disinhibition, and negative emotionality/low dominance. We examined associations between AVPR1a and six personality domains and hierarchical personality dimensions in 129 chimpanzees (Pan troglodytes) living in Japan or in a sanctuary in Guinea. We fit three linear and three animal models. The first model included genotype, the second included sex and genotype, and the third included genotype, sex, and sex × genotype. All personality phenotypes were heritable. Chimpanzees possessing the long form of the allele were higher in conscientiousness, but only in models that did not include the other predictors; however, additional analyses suggested that this may have been a consequence of study design. In animal models that included sex and sex × genotype, chimpanzees homozygous for the short form of the allele were higher in extraversion. Taken with the findings of previous studies of chimpanzees and humans, the findings related to conscientiousness suggest that AVPR1a may be related to lower levels of impulsive aggression. The direction of the association between AVPR1a genotype and extraversion ran counter to what one would expect if AVPR1a was related to social behaviors. These results help us further understand the genetic basis of personality in chimpanzees.

The fourth dimension of tool use: temporally enduring artefacts aid primates learning to use tools

All investigated cases of habitual tool use in wild chimpanzees and capuchin monkeys include youngsters encountering durable artefacts, most often in a supportive social context. We propose that enduring artefacts associated with tool use, such as previously used tools, partly processed food items and residual material from previous activity, aid non-human primates to learn to use tools, and to develop expertise in their use, thus contributing to traditional technologies in non-humans. Therefore, social contributions to tool use can be considered as situated in the three dimensions of Euclidean space, and in the fourth dimension of time. This notion expands the contribution of social context to learning a skill beyond the immediate presence of a model nearby. We provide examples supporting this hypothesis from wild bearded capuchin monkeys and chimpanzees, and suggest avenues for future research.

Behavioural diversity among the wild chimpanzee populations of Bossou and neighbouring areas, Guinea and Côte d'Ivoire, West Africa. A preliminary report

We present a preliminary report on the differences and similarities in material culture among four neighbouring chimpanzee (Pan troglodytes verus) communities. One of these communities includes Bossou, a long-term field site of wild chimpanzees, in Guinea, West Africa. We also conducted surveys of three new sites. Two of those surveyed areas, Seringbara in Guinea and Yealé in Côte d'Ivoire, are located less than 12 km away from Bossou in the Nimba Mountains region, which forms a natural boundary between Guinea and Côte d'Ivoire. The third, Diécké, is situated further south-west, closer to the border with Liberia. During the surveys, we gathered behavioural information about these neighbouring populations of chimpanzees. The differences, as well as similarities, in material culture were tabulated based on our findings. The three behavioural variants found so far involve differences in nut cracking behaviour with regard to the species of nut cracked. Some variation in materials used for nut cracking has also been recorded. However, we still need to establish whether these local variations can be explained by the demands of the physical and biotic environments in which the populations of chimpanzees live. If these alternative hypotheses can be excluded with continuing research at the study sites, these differences are likely to be cultural behaviours that are influenced by the social context and mode, i.e. horizontal, vertical or oblique, of transmission, by the social structure and organisation of each community and/or perhaps by some form of social norms prevalent within these communities.