HEART-RATE PATTERNS UNDER STRESS IN 3 SPECIES OF MACAQUES

Cardiac responses during one hour exposures to three stressful experim ental conditions were compared among juvenile females of three species of the genus Macaca (M. mulatta, M. radiata, and M. fascicularis). M. fascicularis showed the highest overall heart rate, and M. mulatta th e lowest, in all three conditions. The principal difference between sp ecies was in the pattern of change in heart rate over the test session s. Heart rate declined during the hour for all three species in the fi rst two conditions (home cage, navel environment), and the change was most rapid in M. mulatta and slowest in M. fascicularis. In the third and most stressful condition (physical restraint), each species showed a distinct temporal pattern. Heart rate increased over the hour in M. fascicularis, declined in M. radiata, and increased rapidly then decl ined gradually in M. mulatta. Individual differences in heart rate ten ded to be consistent within and across conditions. Correlations betwee n behavioral measures of somatic activity and heart rate were generall y modest. The results are in accord with other behavioral and physiolo gical differences obtained for the same subjects, and suggest that res ponses to environmental stimuli reflect fundamental aspects of tempera ment that may vary substantially even among closely related species. ( C) 1994 Wiley-Liss, Inc.