Social enrichment of the environment with infants for singly caged adult rhesus monkeys

The practicability of social enrichment for singly caged adult rhesus monkeys was examined. Twenty‐nine weaned rhesus monkey infants were removed from breeding troops to avoid overcrowding and were placed with unfamiliar singly caged adults. An adult‐infant pair was considered compatible when (1) the two animals started huddling with each other within the first 5 days after pair formation and (2) the infant showed no signs of depression and took its share from a limited amount of favored food. Adult‐infant pairs were compatible in 90% (26/29) of cases. Compatibility depended neither on the sex, age, and origin of the adult nor on the sex of the infant. There was no evidence that partners lost interest in each other during 7–11 months of follow‐up observations. Three adults exhibiting stereotypical behavior abandoned their peculiar habits after they had lived with their young companions for 4 months. It was concluded that the often‐heard notion that rhesus monkeys are highly aggressive should not prevent simple attempts to provide singly caged animals with a companion.