Agile gibbon, black-handed gibbon, unko
Hylobates agilis

Adult gibbons

In addition to light buffy coloured and blackish animals, many different colour variants are known to exist in this species, like in H. lar. In addition, agile gibbons may also be contrastingly patterned, with different body parts showing different colorations. Unless the provenience of the animal is known, their subspecies identification is often unreliable.

Buffy coloured or light brown animals are particularly common on western Sumatra, whereas black or dark animals are particularly common on the Malayan peninsula and on eastern Sumatra. The two populations have been suggested to represent different subspecies: H. agilis agilis and H. agilis unko, respectively (Marshall and Sugardjito, 1986). Because the subspecies are apparently defined only by the higher proportion of light phase animals occurring in the former and of dark phase animals in the latter, captive individuals cannot be reliably identified, unless their provenience is known. In addition, many intermediate colour variants are known to exist in this species, whose subspecies identification is even more difficult.

The genital tuft in the non-black males is often contrastingly pale (buffy of light yellow), but usually dark in black individuals. Females are not known to exhibit contrastingly light genital fur.

Adult agile gibbons exhibit a moderate degree of sexual dichromatism: Males often have contrasting light cheeks (white, grey, light brown), females often lack these.

Adult female "Singa" (with infant, born on 20 Nov. 1987), Zoo Asson, France, 1 June 1988. Light variant with brown ventral parts.	Adult male "Tout Petit" and adult female "Singa", Zoo Asson, France, 1 June 1988. This black male is the father of the pale infant shown in the previous photograph. The long temporal tufts visible in the female are common in agile gibbons, but not in lar gibbons.
Adult female, Singapore Zoo, 5 March 1993. Intermediate variant. This gibbon is not buffy coloured like the light variant shown above. The almost monochromatic greybrown animal resembles H. muelleri abbotti.	Adult male (Zoo No. 183/1A), Paignton Zoo, England, 22 Oct. 1988. Intermediate variant. This beautifully patterned animal is darker than the previous animals, but still completely different from the typical dark phase shown below. The back shows a warm light brown colour, contrasting with dark brown ventral parts and inner sides the limbs. Notice the light cheek patches and the light genital tuft.	Adult female (Zoo No. 183/2A), Paignton Zoo, England, 22 Oct. 1988. Intermediate variant. This dark animal exhibits areas of light fur colouration including the corona, lower legs and distal back (not visible). The light brow band is almost absent in this individual. This appears to occur more frequently in females than in male and may be age-dependant. Contrasting black feet also occur in H. agilis, similar to H. albibarbis and H. muelleri muelleri.
Adult male, Singapore Zoo, 5 Sept. 1993. Dark variant. Notice the light cheek patches which frequently occur in males of this species.	Adult male "Sebastian", Twycross Zoo, England, 3 Oct. 1988. Dark variant. Not all male agile gibbons exhibit distinct light cheek patches.	Adult male , Taman Safari Zoo, Cisarua, Indonesia, 16 Sept. 1998. Dark variant. In some males, the light cheek patches are pure white.
Adult female, Tierspital Zürich, Switzerland, 25 Sept. 1985. Dark variant. This young adult female shows a distinct light brow band, like most agile gibbons.		Adult female, Ragunan Zoo, Jakarta, Indonesia, 11 Sept. 1998. Dark variant. This female lacks the white brow band; the animals is almost completely black.

Immature gibbons

Adult female "Sabina" (centre), subadult daughter "Shana" (left), juvenile son "Ash" (right) and infant female "Sita" (botton), Twycross Zoo, England, 6 Oct. 1988. Dark variant. The father of the immature animals is shown among the photographs above ("Sebastian"). Notice that the juvenile and the subadult both show a more distinct light brow band than their mother and the infant. The juvenile male is the anly individual exhibiting light cheek patches in this family group.		Juvenile female "Sheila", Taman Safari Zoo, Cisarua, Indonesia, 20 Sept. 1998. Intermediate variant. The individual has a complete, broad white face ring. This characteristic may occur more frequently in immature animals.
Juvenile female, Ragunan Zoo, Jakarta, Indonesia, 11 Sept. 1998. Intermediate variant. This young female shows an almost complete light face ring.	Juvenile female, Ragunan Zoo, Jakarta, Indonesia, 11 Sept. 1998. Light variant: This almost monochromatic lgiht brown animal has a distinct dark cap.