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 manipulations 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 monkey species in their propensity to manufacture and use tools to modify their physical environments. During the past year, new studies of spacial memory capabilities demonstrated that rhesus monkeys of all ages are exquisitely sensitive to the appearance of novel stimuli within a stimulus-rich environment, be they in captive or free-ranging settings. A study of male troop transfer under captive circumstances was initiated, while a field study comparing both behavioral and physiological characteristics of adult males who had joined new troops after natal troop emigration with those who remained solitary after emigration was completed. Long-term longitudinal analyses of mother-infant interactions in the same field setting uncovered a striking dynamic relationship between troop demographics and patterns of maternal care. Cross-species comparisons of mother-infant relationships between rhesus monkeys and Barbary macaques revealed interesting differences between these closely related macaque species in analogous field settings. Finally, extensive studies with capuchin monkeys extended the known range and complexity of their tool-using capabilities, including some previously thought to be exclusive to humans and their hominid ancestors.