Eastern hoolock
Hoolock leuconedys

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Adult gibbons

Adult eastern hoolocks

This species exhibits a strong sexual dichromatism: Males are largely black or blackish brown with contrasting white eye brows, whereas females are light brown or grey brown, often with darker brown ventral area.

Adult males of the eastern hoolock usually have brownish fur on the chest and a brownish, buffy or grizzled genital tuft. The chin often exhibits whitish hairs. The white brow streaks of adult males are well separated with no white hairs between. Adult females may exhibit contrastingly lighter feet.

Eastern hoolock (Hoolock leuconedys) Eastern hoolock (Hoolock leuconedys)
Adult male, Kunming Zoo, China, 20 Nov. 2007. Adult male, Kunming Zoo, China, 19 Nov. 2007.
Dorsal view. The genital tassel of the male is distinctly paler than the surrounding fur.
Adult male, Kunming Zoo, China, 19 Nov. 2007. Same male as on previous two photographs.
Eastern hoolock (Hoolock leuconedys) Eastern hoolock (Hoolock leuconedys) Eastern hoolock (Hoolock leuconedys)
Adult female, Kunming Zoo, China, 20 Nov. 2007.
Note contrasting light feet.
Adult female "Gui-Gui", Kunming Zoo, China, 5 Aug. 1990.
Notice the light cap and white stripe below eyes and across the ridge of the nose.
Adult female "Gui-Gui", Kunming Zoo, China, 5 Aug. 1990.
Eastern hoolock (Hoolock leuconedys) Eastern hoolock (Hoolock leuconedys)
Adult female, Gejiu Zoo, China, 1 Sept. 1990. Adult female "Pan-Pan", Kunming Zoo, China, 17 Aug. 1990.

Immature hoolocks

Eastern hoolock (Hoolock leuconedys) Eastern hoolock (Hoolock leuconedys) Eastern hoolock (Hoolock leuconedys)
Infant male, Kunming Institute of Zoology, China, 4 Aug. 1990. Infant/Juvenile, Beijing Zoo, China, 9 Nov. 1993. Juvenile male "Lai-Lai", Kunming Zoo, China, 5 Aug. 1990.
In adult males of the eastern subspecies, the long genital tassel usually becomes contrastingly lighter. In this juvenile male, the tassel is still black.
Eastern hoolock (Hoolock leuconedys) Eastern hoolock (Hoolock leuconedys)
Juvenile female "Mao-Mao", Kunming Zoo, China, 5 Aug. 1990. Juvenile male (left) and juvenile female, Gejiu Zoo, China, 3 Sept. 1990.
Eastern hoolock (Hoolock leuconedys) Eastern hoolock (Hoolock leuconedys)
Subadult male (left) and female (right), Kunming Zoo, China, 20 Nov. 2007. Subadult male "Jian-Jian", Kunming Zoo, China, 30 Aug. 1990.