Steward, A. L., Sorenson, A., Elliot, K. et al. 2013. Variables affecting indoor pairing success in adult rhesus macaques (Macaca mulatta). American Journal of Primatology 75(S1), 48. (36th Meeting of the American Society of Primatologists Scientific Program, Abstract #60)

In research centers that study primates, pairing unfamiliar subjects is the most costly and difficult problem that staff face. Recent studies in adult rhesus macaques suggest that social competence and sociality, as measured by ease of forming new relationships, is modulated by genetic and experiential factors. We investigated factors believed to influence social competence: genotype, rearing condition, temperament, emotionality, and stress responsiveness measured by infant plasma cortisol levels. We assessed 353 pairings from subjects housed at the California National Primate Research Center (n=176 male and n=177 female adult pairings). Temperament and plasma cortisol were assessed at three to four months of age through the BioBehavioral Assessment program. Pairings were performed during adulthood. Analyses showed successful pairings were less frequent in males than females. For males, greater weight difference resulted in pairing success. Certain early rearing combinations including field caged animals paired with nursery-reared or indoor-mother reared were predictive of male pairing success. Field cage-reared animals paired with indoor mother-reared or nursery-reared animals were less likely to be successful (F(5)=2.305, p<.047). In females, greater absolute differences in infant behaviors characterizing emotionality (F(1)=4.715, p<.031), nervousness temperament ratings (F(1)=5.193, p<.024), and plasma cortisol levels (F(1)=7.710, p<.006) resulted in pairing failures. These results may help reduce amount of time and distress when pairing animals for welfare purposes and help us better understand the social complexities in rhesus macaque society.