Visual scanning by common marmosets (Callithrix jacchus): Functional aspects and the specialrrole of adult males

The rates of visual scanning and vocalizations were studied in a group of captive marmosets (Callinthrix jacchus) after the presentation of five different stimuli (artificial flower, playback of long calls, female/male conspecific, stuffed wild cat) in order to assess the function of visual scanning. Only the presentation of a stuffed cat induced a significant response. The adult males in particular increased their scanning rate and all adult individuals decreased their rate of vocalizations. The results indicate that visual scanning in marmosets is an appropriate measure of vigilance which seems to serve the function of predator detection and avoidance. The strong response of adult males suggests that they play a special role in predator detection.