Vocal response of captive-reared Saguinus oedipus during mobbing

Mobbing is an important component of antipredator behavior for animals from many taxa. Callitrichids are small-bodied primates that mob multiple types of predators. Though there have been several observations of callitrichids mobbing predators in the wild, their anecdotal nature provides only rough descriptions of behavior and vocalizations. Researchers could neither spectrographically identify nor quantify vocalizations owing to the limitations of observing predation in the field. We examined in detail the mobbing response of 1 callitrichid species, the cotton-top tamarin, in captivity. We recorded vocalizations for quantitative analysis and observed behavior qualitatively. We report 3 new vocalizations that had not been described in the original repertoire for the cotton-top tamarin. Analysis of the time course of a mobbing session yielded a pattern in which the highest intensity mobbing vocalizations decreased over the session even though lower intensity vocalizing continued, which may reflect a shifting strategy from mobbing to vigilance. The rate of calling during mobbing sessions differed from the rate of calling during control sessions. We discuss the vocalizations in relation to 2 hypotheses of form and function of antipredator calls. The newly described mobbing vocalizations may have an important impact on the study of mobbing because they represent a class of vocalizations that researchers have largely ignored in studies of callitrichids, thus raising new issues concerning past and future research on antipredator behavior in the family.