Rhesus macaque (Macaca mulatta) infants at NIHAC were randomly selected to be reared with their mothers (MR) or in a nursery by human caregivers (peer-reared, PR). Mother-reared (MR) animals were reared in social groups composed of 8–14 females (about half of whom had same-aged infants) and two adult males. Peer-reared (PR) animals were separated from their mothers at birth and hand-reared in a neonatal nursery for the first 37 days of life. For the first 14 days, they were kept in an incubator and hand-fed. From day 15 until day 37, they were placed alone in a nursery cage and provided a blanket and a terrycloth-covered, rocking surrogate. A bottle from which the infants would feed was fixed to the surrogate. At 37 days of age, they were placed in a cage with three other age-mates with whom they had continuous contact. At approximately 8 months of age, animals (both MR and PR) were placed into age-matched social groups and housed in large indoor-outdoor runs through late adolescence/adulthood (3.5–5 years), at which point the cohorts were divided into sex-limited groups. All procedures described were approved by the NIAAA and NICHD Animal Care and Use Committees.
