Temperament differences between captive Indian and Chinese-Indian hybrid rhesus macaque neonates.

Anecdotal evidence has accumulated from research and animal care personnel regarding the aggressive behavior reported in captive rhesus macaques originating in China. In this study, we compared neonatal temperament, activity, and neuromotor reflexes in 13 Chinese-Indian hybrid and 29 Indian-derived nursery-reared infants. Neonatal assessments were conducted on days 7, 14, 21, and 30, using a test based on the Brazelton Neonatal Assessment Scale developed for use in human newborns. Hybrid infants had lower scores for all items pertaining to orientation and ability to sustain attention. They were also rated as more temperamentally reactive and irritable than the Indian-derived infants. These results suggest that constitutional factors may underlie some of the behavioral differences observed in Chinese- and Indian-origin adults and that these qualities emerge very early in life.