This project investigates how rhesus monkeys and other nonhuman primate species born and raised under different laboratory conditions adapt to placement into environments that contain specific physical and social features of the monkeys natural habitat. Adaptation is assessed by examining behavioral repertoires and by monitoring a variety of physiological systems in these subjects, yielding broad-based indices of relative physical and psychological well-being. The responses of subjects to experimental manipulation of selected features of their respective environments are also assessed in similar fashion. Whenever possible, field data are collected for appropriate comparisons. An additional focus is on investigating the cognitive, behavioral, and social processes involved in adaptation to new settings or circumstances. Capuchin monkeys are employed in many of these studies because they are unique among monkeys species in their propensity to manufacture and use tools to modify their physical environment. Research carried out during FY99 (a) characterized endocrine, immunological, and health status indicators among juvenile rhesus monkeys in a wild-living population on Cayo Santiago island (PR) and related individual differences on these measures to observer ratings of stress reactivity; (b) collected similar data from young adult females, their first-born offspring, and their biological mothers, permitting cross-generational comparisons of relationships among maternal temperament, biobehavioral reactivity, mothering style, and developmental trajectories of offspring; (c) characterized changes in the relationship with mother and in peer interaction patterns for yearling rhesus monkeys following the birth of a younger sibling; (d) documented evidence of male mate choice among the members of the rhesus monkey troop living in the LCEs 5-acre enclosure at the NIHAC; (e) demonstrated significant reductions in heartrate associated with social grooming in rhesus monkeys following agonistic interactions; (f) identified changes in heartrate associated with noninjurious self-directed biting suggesting that such behavior may serve to reduce levels of arousal in rhesus monkeys, paralleling human clinical data; (g) identified unique patterns of hypothalamic-pituitary- adrenal activity and heartrate-vagal tone decoupling in rhesus monkeys with a history of self-injurious biting that resemble patterns seen in human post-traumatic stress disorder; (h) characterized food preferences among capuchin monkeys and demonstrated that such preferences changed as a function of food availability and opportunity for sharing with group members; and (i) documented evidence of a simple barter system among capuchin monkeys involving exchange of tools and food. - primates, field studies, adaptive behavior, heartrate, HPA activity, psychoimmunology, tool-use