International Journal of Comparative Psychology

Group living may confer an advantage on prey animals if individuals help maximise protection from predation. Some evidence suggests that age and sex differences may signify role divisions infight/flight responses. We examined whether captive common marmosets ( Callithrix jacchus ), a group-living primate species, might also show sex and age differences in response to predators and presented predator-based visual and auditory stimuli, individually and simultaneously. No significantsex or age differences emerged in any of the behaviour recorded. However, we found strong evidence that there were individual differences in flight/fight responses depending on the stimulus presented. Inpresenting a taxidermic model of a carnivore visually, five (of the 12) marmosets showed behaviour suggesting cautiousness, whereas five other marmosets displayed risk-taking behaviour (scored asclose proximity to stimulus, mobbing vocalisations and short latency to approach and vocalise). Importantly, cautious and risk-taking individuals did not behave consistently in these roles but changed when presented with the auditory stimulus or the visual and auditory stimuli combined.These results suggest that there may be individual differences in assessing sensory cues and levels offear fulness and risk-taking may vary accordingly. Whether or not such differences confer anadvantage on group living species, it is an entirely new finding that the type of sensory stimulation affects and alters behaviour to a significant extent within an individual and within the same group of primates.