ENRICHMENT EFFECTS ON RHESUS-MONKEYS SUCCESSIVELY HOUSED SINGLY, IN PAIRS, AND IN GROUPS

Many studies have examined the short-term effects of inanimate environ mental enrichment on the behavior of captive primates. Similarly, nume rous studies have examined the behavioral effects of manipulations to the social environment. Few analyses have examined the long-term effec ts of inanimate environmental enrichment or compared the effects of in animate and social enhancements. The behavior of control (n = 49) and enriched(n = 44) rhesus monkeys (Macaca mulatta) was observed from 1-4 years, as subjects spent successive years housed singly, in pairs, an d then in small groups. Social housing condition and/or age of subject significantly affected time spent inactive, grooming, playing, explor ing, and behaving abnormally. Frequency of vocalization was similarly affected. Social housing resulted in more species-typical behavior pat terns than did single caging. Subjects were more socially oriented whe n pair-housed than when living in small groups. Inanimate enrichment d id not affect behavior over a 3 year period, although enhancements wer e well-used by singly-caged yearlings and pair-housed juveniles. Subje cts used enrichment less frequently when housed in groups. The data su ggest that the presence of a social partner(s) led to more beneficial changes in behavior than did the provision of inanimate enhancements f or rhesus monkeys in the studied age range. Therefore, it is concluded that social enrichment should be provided when possible and appropria te, Efforts to enrich the inanimate environment will be most beneficia l when focused on socially-restricted primates.