Development of the female great call in Hylobates gabriellae: A case study.

Although the structure of adult gibbon duet singing has been characterised in most species, little is known about the ontogeny of gibbon song. The present study describes the developmental trajectory of the female great call in a captive infant Hylobates gabriellae female, on the basis of periodic tape recordings made while she participated in the duetting of her parents. The major part of great call development is completed between 5 and 32 months of age, and a differential time course is apparent for different portions of the female great call, raising the question of the role of the protracted period of vocal development in this species.