Gibbon Conservation Center

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.

Hylobates moloch (Audebert, 1798). Moloch, silvery, or Javan gibbon   
General Description: Both sexes are silvery gray and have long, dense hair at the neck, sides of the head, upper arms, and on the shoulders. Either sex may have a distinct light-to-dark gray cap with the same coloration occasionally under the brow (B3349). There is dark-gray hair in the genital region. The adult females chest is sometimes partly charcoal colored (Geissmann, 1995). Both sexes have white to white-gray hair on the brow and surrounding the chin; this hair usually connects to darker hair on the side of the face to form a face ring. Hair under the chin grows upward, giving the appearance of a "goatee". Infants are lighter in color than are adults and change to silvery gray shortly after birth (Groves, 1972). H. moloch is sometimes confused with Mueller's gibbon because of similarities in coat color.

Hylobates moloch, Javan gibbons, live in the fragmented forests of western and central Java, where less than 4000 survive in the wild.  GCC houses 11 Javan gibbons. and 9 Javan gibbons have been born here, which represent the only births in the USA. Currently there are only six institutions in the world that house breeding pairs of Javan gibbons.

CNN article on Javan gibbons

Hylobates muelleri (Martin, 1841). Mueller's, Bornean, or gray gibbon.   
General Description: There are three subspecies. Adult male and female are identical in coat color, which varies from grey to grey-brown. The hair of the adult male's genital tuft is 25 mm long (Marshall & Sugardjito, 1986) and is typically darker than the body hair. Infants' coats are lighter than their parents'. This species lacks a uniform appearance in areas of geographic overlap with other Mueller's gibbon subspecies. The great call of the female Mueller's gibbon is somewhat similar to that of female pileated gibbons. Eastern Mueller's gibbon (H. m. muelleri) and Abbott's gray gibbon (H. m. abbotti) are sometimes difficult to distinguish from moloch gibbons because of similarities in coat color. H. m. funereus is occasionally misidentified as the Bornean agile gibbon (H. agilis albibarbis) for the same reason.

Hylobates muelleri abbotti (Kloss, 1929). Abbott's gray gibbon.  Area: Western Borneo.  Abbott's gray gibbon has short, mouse-gray body hair with dark hair in the genital region. The brow is slightly paler than the head hair. Those populations bordering H. muelleri funereus populations sometimes have black hair on the throat and/or a slightly darker cap and upper chest and inner aspects of the limbs, reflecting subspecific hybridization in overlap zones.

Hylobates muelleri muelleri (Martin, 1841). Eastern Mueller's gibbon.  Area: Southeastern Borneo. The eastern Mueller's gibbon is pale grey with a black cap, ventrum, hands, feet, and inner aspects of the limbs. It has a thick white brow.

Hylobates muelleri funereus (Marshall & Sugardjito, 1986). Northern Mueller's gibbon. Area: Northern Borneo.  Northern Mueller's gibbon is dark gray or gray-brown with black to blackish-brown cap, ventrum, throat, inner aspects of the limbs, and genitals. Outer area of the lower limbs and tips of the fingers and toes are generally paler or buffish-gray. Toes and fingers are black on specimens from southern regions where the subspecies overlap geographically with H. m. muelleri.

Hylobates pileatus (Gray, 1861). Pileated gibbon or capped gibbon.    General Description: This species is not divided into subspecies. Adult males have short, black hair with a thick, white brow band that becomes thinner as it encircles the face. Males' fingers and toes are white, with a slight fringe running halfway up the sides of the hands and feet. There is a white prepubital patch. The crown cap is encircled by a grizzled white streak on the sides of the head that becomes faint on the back of the head. Some adult males have a faint gray grizzling on the lumbar region. Adult females are silver-buff with a black heavily-furred throat, inverted triangle on the ventrum that branches off to the underarm area but stops short of the genital area. This black coloration extends upwards to the bottom of the ears and narrows in front of the ear to connect with the cap. The female's cap is large and black, with long, silver-buff hair curved over the temples. Females have a thin, white brow which sometimes extends laterally around the orbital ridge, and there can be a trace of a white facial ring. Both sexes have a lateral tuft along the crown's sides.  Infants are slightly paler silver-buff than are adult females. H. pileatus is the only species in the genus Hylobates in which males undergo a color change (buff to black). A male completed this transition in 6.5 years. Males can begin their color change at 18 months of age with a small black patch above the sternum. The song of the female pileated gibbon is somewhat similar to that of adult female Mueller's gibbon.    Hylobates pileatus, pileated gibbons, are found only in SE Thailand (approximately 10,000), W. Cambodia (approximately 10,000), and Laos (approximately 10,000).  Half of the pileated gibbon population in the Americas lives at GCC, including the only two breeding pairs in the Americas.  Currently there are only twenty captive breeding pairs of pileated gibbons in the world.