MATERNAL-BEHAVIOR OF PRIMIPAROUS RHESUS-MONKEYS - EFFECTS OF LIMITED SOCIAL RESTRICTION AND INANIMATE ENVIRONMENTAL ENRICHMENT

Many studies have shown that female rhesus monkeys (Macaca mulatta) th at were socially restricted while they were very young were likely to become inadequate mothers, especially to their firstborn offspring. As part of a strategy to convert a traditional breeding colony of rhesus monkeys into a specific pathogen-free (SPF) colony, females (and male s) were housed in their natal social groups for their first year, sing ly for their second year, in male-female pairs for their third year, a nd in small, unimale-multifemale breeding groups for subsequent years. To test whether this social restriction adversely affected the matern al abilities of 42 primiparous females, their distance from their infa nts and maternal behavior were compared with eight primiparous females that had been continuously socially housed according to our standard colony practices, Focal animal observations were conducted on mothers during the first 20 weeks of their first infants' lives. Analyses reve aled that socially restricted (experimental) females did not differ fr om socially housed (control) females in the overall adequacy of their maternal activities. Experimental primiparous females spent less time nursing and in contact with their infants and more time in non-infant- directed behavior than did control females. However, body weights of i nfants did not differ between groups at either 6 or 12 months of age. There were no significant differences when enriched experimental femal es were compared with those that were unenriched, Females that could n ot view social groups while singly housed, spent more time nursing tha n did females that could view social groups, but infant body weights d id not differ. Two factors in our SPF housing strategy were likely to have contributed to the high levels of maternal competence measured in the experimental subjects: (1) allowing infants to remain in their na tal groups for their first year; (2) providing visual access to social groups containing mothers and infants during the years while subjects were singly and pair housed. Rearing competent mothers was a crucial goal for establishing a cost-effective, self-sustaining SPF breeding c olony of rhesus macaques that appears to have been achieved.