Selective Phonotaxis by Cotton-Top Tamarins (Saguinus Oedipus)

When nonhuman animals vocalize, signal receivers are provided with a range of potential acoustic information concerning the signalerʹs body size, sex, individual identity, kinship and group membership. Here we explore whether cotton-top tamarins (Saguinus oedipus) extract such information from their species-typical combination long call using a modification of the phonotaxis assay originally designed for studies of anurans and insects. In each trial, we sequentially played long calls produced by two different individuals and then provided test subjects the choice to approach either speaker location. We quantified selective phonotaxis using two different aspects of subjectsʹ behavioural response: the first approach following stimulus presentation and the total number of times subjects approached toward each speaker location. Results from subjectsʹ first approach indicated that tamarins perceived acoustic differences between long calls produced by cagemates, non-cagemate colony members and foreign tamarins. Specifically, males showed a preference to approach foreign females over familiar ones, while females approached cagemate and homeroom males over foreign males. When the total number of approaches made towards each stimulus was analyzed, results revealed that subjects did not selectively approach cagemates over colony members or colony members over foreign tamarins. Subjects did, however, approach cagemates significantly more often than foreign tamarins. Overall, these results suggest that (i) tamarins are able to use acoustic information encoded within a single vocal signal to assess individuality and degree of familiarity, and (ii) the phonotaxis assay, successfully used in research on anuran and insects, is also a powerful tool for studies of nonhuman primate communication.