Hylobates agilis

Hylobates agilis (Cuvier, 1821). Agile gibbon.
General Description: H. agilis is commonly called the agile, dark-handed, slender (a common name in the 1800s), or active gibbon. This species is subdivided into three subspecies. Males and immature females have whitish brows and cheek patches. The hair of the male's genital tuft is 50 mm long and generally the same color as, or slightly paler than, the body hair (Marshall & Sugardjito, 1986). Females begin to lose their cheek patches at six years of age. Adult females who have been housed in low light conditions or who have nutritional deficiencies may lack the white brow. The great call of the female agile gibbon is somewhat similar to that of the female lar gibbon.

Hylobates agilis unko, the lowland agile gibbon, is highly threatened and indigenous to eastern Sumatra and the northern peninsula of Malaysia.

Hylobates albibarbis, white-bearded gibbon. Area: Southwestern Borneo. The Hylobates albibarbis is light brown with dark-brown to brown-black underparts, hands, feet, and cap and a white brow. H. albibarbis has a song that has longer and slower notes when compared with Hylobates agilis unko and H. a. agilis. Hylobates agilis unko and H. a. agilis are difficult to distinguish from each other, while H. albibarbis is sometimes mistaken for the northern Mueller's gibbon.

Suborder Haplorrhini
Infraorder Simiiformes
Superfamily Hominoidea
Family Hylobatidae
Genus Hylobates
Species Hylobates agilis (agile gibbon)
Hylobates albibarbis (Bornean white-bearded gibbon)
Hylobates klossii (Kloss's gibbon)
Hylobates lar (lar gibbon)
Hylobates moloch (silvery Javan gibbon)
Hylobates muelleri (Mueller's Bornean gibbon)
Hylobates pileatus (pileated gibbon)

Hylobates klossii (Kloss, 1929). Kloss' gibbon. Area: Mentawai Islands.
General Description: Both sexes have black hair and remain this color at all life stages. Kloss' gibbons have short hair, a broad chest, and long legs, thumbs, and great toes. The hair forming the genital tuft is short. There is inter-digital webbing (Groves, 1972). Adults have a small muzzle, and hair on top of the head is flat. Infants crown hair stands erect. The song of the female Kloss' gibbon, particularly the great call, is more similar to those of female pileated (H. pileatus) and Mueller's (H. muelleri) gibbons than it is to female lar (H. lar) and agile gibbons (H. agilis). Kloss' gibbon populations are all classified into one species, but there are some variations in hair length, the direction of hair grown on the outer side of the forearm, and body size on different islands (Groves, 1972, 1984).