Temporal cues in the antiphonal long-calling behaviour of cottontop tamarins

In primates, long-range communication is often mediated by the use of 'long' (or 'loud') calls. Beyond the acoustic classification of these calls and descriptions of the behavioural context in which they are produced, few experimental studies have examined how species-typical information is encoded in the structure of these signals. We present the results of eight experimental conditions designed to isolate the mechanisms underlying the perception of long calls in cottontop tamarins, Saguinus oedipus. Our procedure involved presenting a combination of naturally produced and experimentally manipulated long calls to individuals isolated from their group, and then recording the relationship between signal design and the production of antiphonal long calls by the test subject. Tamarins did not distinguish between normal calls and time-reversed or pitch-shifted long calls, but normal response rates did require the species-typical amplitude envelope. Furthermore, there was suggestive evidence that the number of syllables and the syllable rate may also influence antiphonal calling responses. We discuss these results in terms of the mechanisms of vocal recognition in primates and other taxa.