Silvery gibbons are some of the ‘lesser apes’, which differ from great apes (gorillas, chimpanzees, orangutans and humans) by being pair-bonded and smaller, in not building nests, and in some anatomical features where superficially they are closer in appearance to monkeys than great apes. These gibbons have sliver-gray fur which is long and fluffy, and have darker markings on the cap and chest. They have long legs and long arms that have long fingers with reduced thumbs, which are all adaptations for swinging from branch to branch, arm over arm).
The Silvery gibbon is native to the western part of Java, Indonesia. It occurs in the upper canopy of the hill and lowland forests. They spend most of their time up in trees, rarely descending to the forest floor.
Groups of Silvery gibbons usually consist of a mated pair, their infant and a juvenile, the average group size being four individuals. They are diurnal animals, and are highly territorial, defending their territories with "singing." Each morning, the female will announce to the forest her presence by calling and shrieking, often being heard as far as a kilometer away. Silvery gibbons swing from branch to branch to move around the forest. They can walk on the ground when necessary, walking on two legs with their arms held above their heads for balance.
Silvery gibbons are monogamous, mating for life. Breeding occurs at any time during the year. Females produce one baby every 2 to 3 years or so. Gestation lasts 7 to 8 months. The mother keeps her baby close to her for warmth and nurses it for about a year. Offspring live with their family group until they are fully mature at around 8 years old, when they are ready to go and find a mate. Families are usually very tightly bonded and stay close to each other when traveling.
The Silvery gibbon is threatened with extinction as a result of forest degradation, the clearing of land for agricultural purposes and the illegal wildlife trade. Infants are taken from their mothers to be sold in the illegal market, the mother often being killed in the process.
According to the IUCN Red List, the total number of Silvery gibbons is fewer than 2,500 mature individuals. Their population numbers are decreasing today, being classified as endangered (EN) on the list of threatened species.