The black crested gibbon (Nomascus concolor) is an endangered species of gibbon found in China, Laos, and northern Vietnam, with four subspecies. The length from the head to the end of body is 43–54 cm (17–21 in) and it weighs from 6.9 to 10 kg (15 to 22 lb). The species exhibits sexual dichromatism, the male is almost completely black, but sometimes with white or buff cheeks, while the female is a golden or buff colour with variable black patches, including a black streak on the head. Gibbons are forest dwellers and are well known for their habit of swinging between the branches of the rainforest on their long arms, a method of locomotion known as brachiation. Gibbons are also adept, however, at walking upright, both on the ground and in the trees. Black crested gibbons live in small family groups consisting of a monogamous male and female and their offspring; occasionally groups reportedly may contain additional mature females. These apes are predominantly arboreal and the group forages and sleeps amongst the trees. Led by the female, the breeding pair partakes in vigorous bouts of singing in the morning, which hauntingly echo through the forest. These ‘duets' are believed to be essential in pair bond formation and reinforcement, and also serve to advertise the presence of the group within the territory.

(source: wikipedia)