Heart rate and body temperature in separated monkey infants

Heart rate (HR) and body temperature (BT) were recorded from ten unrestrained group-living M. nemestrina (pigtail) monkey infants, using totally implantable multichannel biotelemetry systems, during a 4-day base line (preseparation) period, during the agitation-depression reaction accompanying 4 days of maternal separation, and for several days following reunion with the mother. Quantified behavioral data were collected in nine of the ten infants. Mean daytime (1000 to 1600 hr) and nightime (2200 to 0400 hr) HR and BT values were computed for each infant, and for the group as a whole. The behavioral agitation reaction immediately following separation was accompanied by increases in both HR and BT. Beginning with the first night of separation, both HR and BT showed marked decreases from base line. Whereas group mean HR and BT changes were maximal early in the separation, behavioral indices of depression tended to be maximal later in the separation period. Reunion with the mother tended to normalize HR and BT in most infants. Two infants exhibited sudden transient reversible drops in nocturnal BT well into the separation period, suggesting an impairment in thermoregulatory mechanisms during the period of depressive behavior. One infant had a prolonged separation-induced decrease in HR that persisted throughout reunion, indicating that the stress of maternal separation may induce physiological changes that considerably exceed the duration of the effective stress.