Comparative Personality Assessment of Three Captive Primate Species: Macaca nigra, Macaca sylvanus, and Saimiri sciureus

Comparative studies of primate personality offer informative insights into the evolutionary origins of personality structure in primate species. Primate personality research has, however, focused on a limited number of species. We investigated personality in three relatively understudied species: Sulawesi black crested macaques (Macaca nigra), Barbary macaques (Macaca sylvanus), and common squirrel monkeys (Saimiri sciureus). We sent a 38-item questionnaire to all European zoological institutions holding the study species and keepers were required to rate individuals on all items. Assessments achieved good levels of interrater reliability. Principal components analysis (PCA) revealed Sociability and Dominance personality dimensions in all study species, an Emotionality dimension in both M. nigra and M. sylvanus, a Cautiousness dimension in S. sciureus, and a Human-Animal Sociability dimension in M. sylvanus. Sociability and Dominance dimensions were shown to have good construct validity, as assessed through appropriate relationships with sex and age and correlations with behavioral measures. The Sociability, Dominance, Emotionality, and Cautiousness dimensions were comparable with analogous dimensions in other primate species but aggressive-type traits did not load onto the Dominance dimension in the two Macaca spp. We suggest that this may be attributed to their more tolerant social systems compared to those of other primate species. The Human-Animal Sociability dimension could not be compared with other primate studies as, to date, there has been limited investigation of human-directed personality dimensions in captive primates. Our findings suggest that the two Macaca species are more similar to each other, in terms of their personality structure, than either is to S. sciureus, which suggests phylogenetic similarity is an important predictor of personality. However, further comparative analysis of a wider range of primate species is needed to inform theories regarding the evolution of primate personality structure.