Attention-getting in a white-cheeked gibbon by means of a novel vocalization?

Gibbons (family Hylobatidae) are renowned for their melodious territorial songs but other aspects of their acoustic communication have received little research attention. Here we describe an apparently novel idiosyncratic non-song vocalization in an adult captive Southern white-checked gibbon (Nomascus siki), which we suggest acts specifically in attracting a human's attention. For this preliminary report we analysed 25 individual calls recorded over a period of 6 months. Typically, calling is accompanied by clapping and feet-slapping, behaviours not reported from gibbons in comparable situations so far. The utilization of both innovative vocalizations and other acoustic displays as human-directed attention getters, reminiscent of our white-checked gibbon subject. is known from great apes, which further suggests a concordant behavioural function. However, the gibbon's displays, despite their unequivocal novelty, could also represent unintentional behavioural responses related to frustration. Eventually, experimental approaches are required to clarify what underlies this unusual behaviour.