Black-crested gibbon  (Nomascus concolor)

The black-crested gibbon is one of the world's most endangered primates and may be on the very brink of extinction (7). Males and females are strikingly different in appearance with males almost completely black, but sometimes with white or buff cheeks, and females a golden or buff colour with variable black patches, including a black streak on the head (2). The common name of this species comes from the tuft of longer fur on the crown of the head (5). Both sexes have the characteristic slender shape of the ‘lesser ape' with long arms and legs, grasping hands and feet, and no tail (4). A variety of calls are produced, which are amplified with the aid of a throat sac below the chin; males and females engage in duets, in which males grunt, squeal and whistle whilst females sing rising notes and twitter (2).