2. Species Descriptions

In the present section, the vocal characteristics of each species and the type of call bout produced by mated animals are briefly described. For each species, two sonagrams are provided, the first one (a) showing fully developed male phraes, the second one (b) showing a great-call sequence of the female, with or without male contribution, depending on whether the species produces duet songs or not.

All vocalisations for the sonagramms were recorded from captive specimens by the present author, unless noted otherwise. Female and male songs recorded in the wild (Marshall & Marshall, 1976; Marshall & Sugardjito, 1986; Geissmann, own observations) are virtually identical to those recorded from captive gibbons during the present study.

In order to show variability, sonagrams of two different phrases are provided for males of the genus Hylobates. In H. klossii, these stem from the same male; in all other cases, two different individuals are shown. Male contributions to the great-call sequences uttered at the same time as female vocalisations are underlined with a purple line, while those uttered solo by the male are underlined with a blue line.