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.

Social relationships between immigrant and resident bonobo (Pan paniscus) females at Wamba

Social relations and behaviours of adolescent female pygmy chimpanzees (Pan paniscus) that migrated between unit groups were studied at Wamba, Zaïre. Each immigrant female selected one particular resident female, a 'specific senior female' (SSF) and frequently approached and followed her. Affinitive behaviours (e.g. grooming, genitogenital rubbing) were frequently performed between the immigrant and her SSF. Most affinitive behaviours were more likely to be initiated by the immigrant than by her SSF. The immigrant's relationship with her SSF seemed to facilitate the immigrant's integration into the new unit group. Resident males actively approached and mated with the immigrant females. Copulation also appeared to further the immigrant's stable relationship with the resident males.