Differences between Saimiri sciureus and Callicebus moloch in physiological responsiveness: implications for behavior.

The New World primates Callicebus moloch and Saimiri sciureus differ markedly in life modes. Physiological responsiveness (heart rate, cortisol) of these related taxa was compared in two situations that differed in the presumed degree of stress imposed, exposure to a novel environment and physical restraint. In both situations, Saimiri exhibited higher initial levels of heart rate and corticosteroids. In addition, the species differed in their patterns of response to both situations. Saimiri maintained initial heart rate levels across a 1-hour exposure period, whereas Callicebus showed a marked and continuous decline in heart rate. Adrenocortical activity increased in both species in response to test situations, but the elevations in plasma corticosteroids were substantially greater for Saimiri than for Callicebus. The results indicate that the species differ with respect to organization of physiological regulatory systems in a manner consistent with behavioral contrasts between them.

Olfactory and visual differentiation of synthetically scented surrogates by infant squirrel monkeys.

Twelve infant squirrel monkeys were reared with distinctively colored and scented inanimate surrogates (Green/Floral or Black/Clove) and tested monthly from 1 to 6 months of age in 3 paired-comparison conditions that assessed the efficacy of synthetic olfactory cues and color cues as attractive properties of the surrogates. The infants developed specific attractions to both the rearing odor and color of the surrogates by approximately the end of Month 4, although substantial differences existed between the 2 rearing groups, particularly with respect to color responsiveness. When compared with previous findings on infant squirrel monkeys reared with naturally scented surrogates, odor preferences developed relatively late, suggesting that natural, species-typical odors may have inherently stronger attractive properties for Saimiri than arbitrary synthetic odors.