Personality in wild bonobos (Pan paniscus).

To understand the evolution of personality structure requires examining personality dimensions in multiple species using a common set of traits. Little research has been conducted on personality in wild populations of nonhuman primates. Using behavioral observations and questionnaire ratings, we examined factors influencing personality in 16 wild bonobos (Pan paniscus) at Wamba, Luo Scientific Reserve, Democratic Republic of the Congo. We extracted five factors from 31 of the items from the Hominoid Personality Questionnaire (HPQ) and three factors from observed behaviors. The HPQ factors were labeled Unemotionality , Friendliness , Aggressiveness , Irritability , and Activity . The behavioral factors were labeled Grooming , Playfulness , and Introversion . We established the convergent and divergent validity of these factors by obtaining correlations between the HPQ and behavioral factors. We tested for sex differences and found that males were significantly higher on Introversion and significantly lower in Irritability . We then tested for age differences and found that Friendliness was lower and Aggressiveness was higher in older individuals. Finally, we found that, among males, hierarchical rank was associated with higher Aggressiveness . These findings contrast with findings in chimpanzees in ways consistent with known species differences. For one, consistent with the more egalitarian structure of bonobo society, we did not identify a clear Dominance factor. Also, the results related to sex differences were consistent with previous findings that reveal closer bonds between female bonobos than female chimpanzees. These findings highlight the importance of studying personality in closely related species and the need to consider species' socioecology when studying personality. Am. J. Primatol. 78:1178-1189, 2016. © 2016 Wiley Periodicals, Inc.