Supplementary material to BEH 3635

Video A1. Dorian engaging in the typical multimodal display accompanying his idiosyncratic vocalizations. The gibbon is repeatedly gazing towards the kitchen room next to his enclosure, perhaps expecting the appearance of a keeper. The animal was filmed from behind a barrier, probably unaware of the recording person.

Audio A1. Exemplary idiosyncratic vocalizations of Southern white-cheeked gibbon Dorian.

Audio A2. Exemplary play grunt of Northern white-cheeked gibbon Elliott.