Unlike other gibbon species, Müller's Bornean Gibbon does not show sexual dimorphism in its fur coloration. Its fur is grey or brown colored with a ring of bright fur around its face. On the head it often has a darkly colored cap. With an average weight of 5.7 kg, it ranks among the smaller of the gibbons.
Müller's Bornean Gibbon is endemic to the island of Borneo, it inhabits the northern and eastern part of the island. In the southwest of the island the Agile Gibbon lives, and surprisingly their territories hardly overlap. They are diurnal rain forest dwellers that are characterized by the long arms that all gibbons have, with which they brachiate through the trees. The Grey Gibbon lives together in monogamous pairs, and defend their family territory against intruders with long, loud singing, which rings out above all else early in the morning. Its diet consists primarily of fruits. Little is known about the reproductive patterns of this species, but it is thought to be similar to that of other gibbon species.
