Adaptation Of Laboratory Reared Monkeys To Environments

Child Health And Human Development

Investigators

Linked publications & trials

Abstract

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. In this program of research adaptation is assessed by examining behavioral repertoires and by monitoring a variety of physiological systems in monkeys throughout the lifespan, 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 and circumstances. This past year we completed the data collection for a study in which some nursery-reared rhesus monkey infants ("masters") were given operant control over access to highly desirable food treats, whereas other nursery reared infants ("yoked controls") received the same treats in the absence of any control. Preliminary analyses of behavioral data collected both in the infants' home cages and in a novel environment indicated that the "master" subjects engaged in more exploratory and less anxious-like behavior, and had lower levels of HPA activity, than their yoked control counterparts. Additional analyses of CSF monoamine metabolite concentrations are currently underway. A second study completed this past year examined the effects of increasing the amount of physical handling of nursery-reared rhesus monkey infants by LCE nursery staff on behavioral development, HPA activity, and CSF monoamine metabolite concentrations. One group of nursery-reared infants received an "extra" 32 minutes of handling over that typically experienced by rhesus monkey infants reared in the LCE neonatal nursery throughout their first 139 days of life. The infants receiving the extra physical handling consistently exhibited significantly lower levels of ACTH when tested under standardized conditions, beginning at 30 days of age and continuing beyond the period of extra handling, relative not only to their nursery-reared counterparts receiving standard nursery care but also compared with same-age infants reared by their biological mothers. Analyses of the behavioral and CSF monoamine metabolite data are currently underway. Two new methodologies were developed and pilot-tested this past year in the LCE nursery. The first involved the development of an apparatus named the Saliva Procurement Integrative Tool (SPIT) for repeated noninvasive collection of saliva samples from several nursery-reared rhesus monkey infants. The device is constructed of inexpensive, readily available materials, and it allows investigators to sample multiple infants simultaneously without being present during the actual saliva collection. The second methodology utilized small accelerometers housed inside wristwatch-sized cases placed within modified commercially available small nylon pet harnesses carried on the backs of nursery-reared infants housed both individually and in small social groups. These accelerometers were then used to monitor the physical activity every 15 minutes in each infant over several 96-hour periods throughout development. Data from an initial study monitoring the activity levels of differentially reared infants during their fourth and fifth months of life are currently under analysis. Another study explored the relationship between adrenocortical reactivity and object manipulation style measured in infant, juvenile, and adult capuchin monkeys and object manipulation style and proficiency in a tool-using task assessed 4 years later. Individual differences in object manipulation style among monkeys of all ages were predictive of individual differences in both object manipulation style and successful tool use later in life. Among infants and juveniles, manipulation and success in both the initial and subsequent tool-using tests were negatively correlated with plasma cortisol concentrations; among adults there were no significant correlations between tool-using scores and cortisol reactivity. Finally, this past year we published the results of a study examining continuity and change in patterns of adrenocortical functioning throughout the juvenile years in rhesus monkeys reared in 3 different physical and social environments for their first 7 months of life but thereafter placed together and subsequently maintained in large peer groups until puberty. Monkeys from all 3 rearing conditions (mother-peer, surrogate-peer, and peer-only) exhibited significant increases in plasma cortisol over their first 5 months but then showed steady declines from 1 to 3 years of age; females consistently had higher concentrations than males at all ages. Plasma cortisol levels of surrogate-peer reared subjects were lower than were those of their mother-peer reared counterparts (with peer-only reared subjects intermediate) during the first month of life but not at later ages. Juvenile cortisol levels were significantly correlated with infant levels in all samples collected after two weeks of age, indicating long-term developmental stability of individual differences. Saliva samples were collected from a subset of these subjects at 1, 2, and 3 years. Analysis of salivary cortisol concentrations from this subgroup revealed a significant age-related decline, as well as lower levels for surrogate-peer reared monkeys at each age, but no significant sex differences at any age. Comparison of salivary and plasma cortisol values obtained from the same subjects yielded a highly significant positive correlation.