Differences among three macaque species in responsiveness to an observer

Behavioral responses of experimentally naive captive-born juvenile females of three macaque species (Macaca mulatta, M. radiata, M. fascicularis)to a passive human observer were compared across three periods, beginning approximately 6 weeks after animals were transferred from multianimal groups housed outdoors to individual cages in colony rooms and ending approximately 6 months later. Responsiveness was assessed using eight relatively stereotyped behavior patterns characteristic of this genus. Although overall responsiveness declined across periods in all groups, this measure was consistently highest for M. fascicularis.Patterns were also analyzed as indicative of “fear” or “hostility.” Responses of M. fasciculariswere frequent in both categories, although fear scores exceeded those for hostility. M. mulattascored more frequently as hostile than as fearful. Both fear and hostility scores for M. radiatawere extremely low. The only response shown with more than minimal frequency was lip-smacking, a pattern that is usually construed as an appeasing, submissive, or affiliative display. Differences among species in their responses to the observer are generally consistent with other behavioral and psychophysiological data on the same subjects and with patterns of social interaction between conspecifics.