Degree of Chinese ancestry affects behavioral characteristics of infant rhesus macaques (Macaca mulatta)

The use of Chinese-origin macaques in biomedical research is problematic for some scientists because of the reported behavioral and physiological differences from those of Indian origin. However, few studies have examined the effects of varying degrees of Chinese ancestry (DCA) on behavior, and they were typically based on small sample sizes and unusual rearing conditions.

Using data from a colony-wide program, we examined whether DCA was related to behavior and temperament ratings reflecting emotionality (fearfulness, aggression, and anxiety) and activity. The 249 subjects, born and reared in an outdoor social environment, were separated from their groups for a 25-h period of indoor testing. Their DCA (range: 0.6-99.4%) was determined by analyzing the frequency of short tandem repeat alleles.

The major effect of DCA was on fearfulness, with the more hybridized animals scoring lowest and the more pure Indian- and Chinese-origin macaques resembling each other.