White-bearded gibbon, H. albibarbis

Adult gibbons

The white-bearded gibbon (H. albibarbis) usually exhibits a particularly contrasting colouration (with dark chest and cap, and black hands and feet). Similarly coloured animals may also occur in populations of H. agilis, although they usually (but not always) lack the contrasting black hand and feet. Hylobates muelleri muelleri may also be of similar colouration but is often more gray than brown. In addition, males in H. albibarbis usually have a longer genital tuft than males of H. muelleri (5 cm vs. 2.5 cm). The genital tuft in males of H. albibarbis is often contrastingly pale (buffy of light yellow), but usually dark in H. muelleri.

Adult agile gibbons and white-bearded gibbons exhibit a moderate degree of sexual dichromatism: Males often have contrasting light cheeks (white, grey, light brown), females often lack these. In addition, the genital tuft is often contrastingly light coloured in males of intermediate colour phases (but apparently never in males of the black phase). In female agile and white-bearded gibbons, the genital hair is not contrastingly light.

Adult male "Bejo", Tuanan Orangutan Research Station, Southwest-Kalimantan, 2006. Photo: Livia Haag.	Adult male "Bejo", Tuanan Orangutan Research Station, Southwest-Kalimantan, 2006. Photo: Livia Haag. The light genital tuft is well visible.
Adult male, Guangzhou Zoo, China, 7 Sept. 1990. Note the contrasting colouration, the black hands (not visible) and feet, and the light genital tuft. This warmly coloured individual has particularly long hair around the face and in the corona.	Adult male, Singapore Zoo, 5 Sept. 1993. This one-armed male is less warmly and less contrastingly coloured, but the distinctive black hands and feet and the light genital tuft are well visible.	Adult male "Raymond", Taman Safari Zoo, Cisarua, Indonesia, 20 Sept. 1998. This dark gibbon has a greybrown back and legs. The feet are contrastingly white, the genital tuft is light grey.
Adult female "Juminten", Tuanan Orangutan Research Station, Southwest-Kalimantan, 2006. Photo: Livia Haag.		Adult male "Bejo" and female "Juminten" copulating, Tuanan Orangutan Research Station, Southwest-Kalimantan, 2006. Photo: Livia Haag. The male's cheek patches are lighter than those of the female.

Immature gibbons

Infant male "Sutejo" (c.1.5 years old) playing with his subadult sister "Paimin" (head not visible), Tuanan Orangutan Research Station, Southwest-Kalimantan, 2006. Photo: Livia Haag.	Infant male "Sutejo" (c.1.5 years old) playing with his father "Bejo" (head not visible), Tuanan Orangutan Research Station, Southwest-Kalimantan, 2006. Photo: Livia Haag.
Subadult male, Ragunan Zoo, Jakarta, Indonesia, 11 Sept. 1998. Note the contrasting colouration, the black hands and feet, and the light genital tuft. This young male has particularly bright and broad white cheek patches.	Subadult female "Paimin", Tuanan Orangutan Research Station, Southwest-Kalimantan, 2006. Photo: Livia Haag.	Subadult female "Paimin", Tuanan Orangutan Research Station, Southwest-Kalimantan, 2006. Photo: Livia Haag.