Gibbons

(Hylobatidae), a family of small anthropoid apes of the order Primates.

The arms of gibbons are exceptionally long (span to 2 m). Cheek pouches and tail are absent. There are small ischial callosities. There are two genera—the gibbons proper (Hylobates), including six species, and the larger siamangs or syn-dactyl gibbons (Symphalangus), represented by the single species S. syndactylus, which have a cutaneous membrane joining the second and third toes. The length of the male’s body in the gibbons proper is 40-64 cm and the weight, from 4 to 8 kg. The siamang male is 47-60 cm long and weighs 9.5-12.5 kg (sometimes up to 20 kg). Sexual dimorphism is not pronounced. The hair is thick, and it varies greatly in color from gray or yellowish brown to (in the black gibbon and the siamang, for example) black. Gibbons are found in southern China, Indochina, the islands of Sumatra, Java, and Kalimantan. The siamangs are native to Sumatra and the Malacca Peninsula (in the state of Selangor). All gibbons live in trees, where they move about with great facility and speed. They throw themselves from branch to branch, at distances up to 10-12 m, using their arms alone (brachiation), or they run across the branches on their legs, balancing themselves with their arms, as they do on the ground. They often stay in pairs or in small groups of six, although sometimes these groups may consist of up to 20 or 30 individuals. They feed on fruits, leaves, buds, flowers, insects, bird eggs and nestlings. Gibbons do not make nests; they sleep in the thick foliage in the branches. The gibbon’s cry, especially that of the black gibbon and the siamang, which has large laryngeal sacs, is very loud. Gestation lasts from 210 to 235 days. The young are born at any time of the year. They reach sexual maturity when five to ten years old, and the life-span is 30 to 35 years. Gibbons are relatively uncommon in zoos.