BEHAVIORAL-EFFECTS OF ENRICHMENT ON SINGLY-HOUSED, YEARLING RHESUS-MONKEYS - AN ANALYSIS INCLUDING 3 ENRICHMENT CONDITIONS AND A CONTROL-GROUP

Three cohorts of yearling rhesus monkeys (Macaca mulatta) were maintai ned in single cages for one year as part of a derivation program to pr oduce a breeding colony of specific pathogen-free (SPF) monkeys. Durin g this year of social restriction, subjects were provided with three d ifferent types of environmental enrichment (physical, feeding, and sen sory) to counteract the known effects of social restriction and to qua ntify the effects of these different conditions of enhancement on thei r behavior. Focal animal observations were conducted on enriched and c ontrol subjects for all cohorts. Enrichment conditions were presented in a different order to each cohort. Monkeys provided with enrichment spent significantly more time playing and less time self-grooming than did control monkeys in unenriched cages, suggesting that the overall enrichment program was of some benefit to the monkeys, because these c hanges in behavior were in species-typical directions. Among enriched subjects only, there were significant differences in the amount of tim e spent drinking, grooming, feeding, playing, exploring, and using enr ichment across the three enrichment conditions. Both the physical and feeding enrichment conditions led to species-appropriate changes in be havior, therefore enhancing psychological well-being as some define it . Sensory enrichment was of little benefit. The first cohort was house d indoors, received less stimulation from the environment outside of t he single cage, and used enrichment more than did the other two cohort s housed outdoors. This suggests that the external environment influen ces behavior in the single cage and that enrichment may be most effect ive for animals housed indoors. (C) 1995 Wiley-Liss, Inc.