A COMPARISON OF THE EFFECTS OF SIMPLE VERSUS COMPLEX ENVIRONMENTAL ENRICHMENT ON THE BEHAVIOR OF GROUP-HOUSED, SUBADULT RHESUS MACAQUES

Enrichment of the environments of captive primates is currently of int erest as both a basic and an applied research question, particularly w hen social and inanimate enhancements are used simultaneously. We meas ured the behavioural effects of two intensities of inanimate enrichmen t on 12 unimale-multifemale groups and 12 all-male groups from three c ohorts of three to four-year-old rhesus macaques (Macaca mulatta). Hal f of the groups received a simple, inexpensive enrichment programme wh ile the other groups received a more complex and costly combination of physical and feeding enhancements. Observations were conducted on 93 subadults of both sexes during their initial year of group housing. In tensity of enrichment did not differentially affect the amount of time subjects spent in any of the activities analysed. Subjects that recei ved the more complex programme spent only 8.3 per cent of their time u sing the extra enhancements. Therefore, there was little demonstrated benefit of the more costly enrichment programme. The three cohorts dif fered in the amount of time that they spent inactive, behaving agonist ically, playing and located near a group mate. A planned comparison of one cohort that had been single-housed without visual access to socia l groups, to the two cohorts that had visual access to social groups d uring single caging, revealed differences in play and socially-located behaviour, which may have been due to differences in extra-cage condi tions two years prior to the present study. When primates are housed s ocially with conspecifics as 'social enhancements', the relatively sim ple inanimate enrichment programme we used was as effective as the mor e costly programme. When enrichment resources are limited, inanimate e nrichment efforts should be focused on monkeys that are not socially e nriched.