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 monkey=s 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 FY98 (a) identified significant gender and maternal rank influences on the development of independence by rhesus monkey infants reared by their mothers in the LCE=s 5-acre outdoor enclosure at the NIHAC that mirror patterns reported for field populations of rhesus monkeys; (b) documented changes in mother-yearling relationships associated with the birth of a new sibling in wild-living rhesus monkey populations on Cayo Santiago (PR); (c) demonstrated significant relationships between heartrate and adrenocortical responsiveness and specific aspects of maternal and group-directed behavior for adult females in the Cayo Santiago rhesus monkey populations; (d) generated lifespan longitudinal behavioral profiles for group-living rhesus monkey adults housed in indoor pens that revealed remarkable stability of both individual and gender-specific profiles from early adulthood to senescence, despite significant developmental changes in specific behaviors as a function of increasing age; (e) expanded the known range of complex tool-using behaviors in captive capuchin monkeys, including both tool- and food-sharing between different social groups; (f) characterized developmental, postural, and task-specific aspects of laterality in capuchin monkeys; and (g) identified factors contributing to individual differences in tool-use proficiency in this unusual primate species.