|Silvery Gibbon range|
The silvery gibbon (Hylobates moloch) is a primate in the Hylobatidae or gibbon family. Its coat is bluish-grey in colour, with a dark grey or black cap. Like all gibbons, silvery gibbons lack external tails, have dorsally placed scapulae, and reduced flexibility in their lumbar regions. They have long, curved fingers and very long forelimbs relative to their hind limbs. On average, they reach 8 kg in weight.
The silvery gibbon lives exclusively on the island of Java (Indonesia), where it inhabits deeply hidden portions of the rain forests. It is diurnal and arboreal, climbing trees skilfully and brachiating through the forests. Brachiation is aided by the possession of mobile wrist joints, full rotation of the upper arm, and the ability to lock elbows in suspension. Its diet consists of fruits, leaves, and flowers.
Every three years, on average, the female births a single young, after a seven-month gestation. The offspring is nursed for about 18 months and lives with the family group until it is fully mature at about eight to ten years old.
Threats and conservation
The silvery gibbon ranks among the most threatened primates. It is listed as Endangered on the 2009 IUCN Red List of Threatened Species, with the population appearing more stable than in a 2004 assessment of the species being Critically Endangered, which suggested there was a 50% chance of the silvery gibbon becoming extinct within the next decade. Habitat destruction on densely populated Java continues to reduce the natural range of the species. Many gibbons are also lost to the illegal pet trade, when adults are hunted so their young can be sold in the markets as pets. Less than 2,000 silvery gibbons in the wild are considered to be genetically viable for the continuation of the species. There are also a dozen small, nonviable populations. Aside from these wild populations, many silvery gibbons are held as pets throughout Indonesia. Gunung Halimun National Park is able to sustain a population of 1000 gibbons.
Several zoos operate silvery gibbon breeding programs. Despite these efforts, the future survival of this species is in question.
Like all gibbon species, the silvery gibbon lives in pairs and stakes out territory that the pair strongly defends; it has relatively small territories of about 42 acres. Females sing to declare their territory several times a day, and if strangers are spotted, the male screams loudly in an attempt to scare them away. The males are usually very aggressive to others.
Some experts recognize two subspecies of Hylobates moloch:
- Western silvery gibbon or western Javan gibbon, H. m. moloch
- Eastern silvery gibbon or central Javan gibbon, H. m. pongoalsoni
These subspecies are not recognized by the IUCN Red List.
- Groves, C. P. (2005). Wilson, D. E.; Reeder, D. M, eds. Mammal Species of the World (3rd ed.). Baltimore: Johns Hopkins University Press. p. 180. OCLC 62265494. ISBN 0-801-88221-4.
- Andayani, N., Brockelman, W., Geissmann, T., Nijman, V. & Supriatna, J. (2008). Hylobates moloch. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 4 January 2009.
- "The Silvery Gibbon Project". Retrieved 2007-12-11.
- Geissmann, Thomas. "Gibbon Systematics and Species Identification". Retrieved 2006-04-13.
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