Richard Lydekker

“ The extreme length of the limbs and the absence of a tail are other features of these small apes, which are thoroughly arboreal in their habits, and make the woods resound with their unearthly cries at night. In agility they are unsurpassed; in fact they are stated to be so swift in their movements as to be able to capture birds on the wing with their paws. ”

“ When they descend to the ground—which they must often do in order to obtain water—they frequently walk in the upright posture, either with the hands crossed behind the neck, or with the knuckles resting on the ground. Their usual food consists of leaves and fruits. Gibbons may be divided into two groups, the one represented by the siamang, Hylobates (Symphalangus) syndactylus, of Sumatra and the Malay Peninsula, and the other by a number of closely allied species. ”

“ A female of the Hainan gibbon (H. hainanus) in confinement changed from uniform sooty-black (without the white frontal band of the black phase of the hulock) to puce-grey; but it is probable that this was only an individual, or at most a sexual, peculiarity. The range of the genus extends from the southern bank of the Bramaputra in Assam to southern China, the Malay Peninsula, Java, Sumatra and Borneo. ”