The Javan gibbon is a small ape, one of 17 currently recognized species (Kim et al. 2010).
It is charachterised by distinctive long silver-grey fur. Both males and females have a black cap on the top of their head and lighter eyebrows.
Javan gibbons have long arms and legs, long fingers and reduced thumbs, all of which are adaptations for brachiation, a form of locomotion where they swing by placing one arm in front of the other.
The males call is a simple ‘hoot’, whilst the calls of females are more variable. Both sexes also give a ‘scream’ alarm call. The female generally calls at sunrise whilst the male guards the territory. The Javan gibbon is one of only 2 gibbon species that do not perform a duet (Silvery Gibbon Project 2012)
Weight varies between 7-9kg for a mature adult.
Habitat and Distribution
The Javan gibbon is endemic to the island of Java, Indonesia. Originally distributed throughout the island, they are now only dispersed in the western half and central west areas of Java in small fragmented populations (Kim et al. 2010).
Javan gibbons inhabit tropical lowland, hill and montane rainforests between sea level and 1500 meters. The Javan gibbon is arboreal using trees for resting, foraging and as a mode of locomotion (MacDonald et al. 2001).
The Javan gibbon is classified as Endangered (EN) on the IUCN Red List (2011)
This species is heading towards extinction due to forest degradation, clearing of land for agriculture and the illegal trade of wildlife.
Infants are pulled from mothers to be sold on the illegal market. The mother of the infant is often killed in order for poachers to obtain the young.
Based on current estimates, the wild populations are thought to number between 400 and 3,000 animals. Many of these are confined to small fragmented areas of forest and considered to be unviable populations (Silvery Gibbon Project, 2012).
Frugivorous diet consisting of approx 63% fruit, 24% leaves and 13% flowers (Kim et al. 2010)
Activity budgets of wild studied Javan Gibbons spent 36% of time feeding, 41% resting, 15% traveling, 6% engaging in social behavior, and 2% in aggressive interactions (Kim et al. 2010)
Breeding and Lifecycle
Male and female Javan gibbons are monogamous, living in family groups with around three to four offspring who disperse at maturity (6-8yrs).
Gestation is approximately 200-210 days. The inter birth interval is 2.0-3.0 years depending on the female. Javan Gibbons in zoos have lived until 50 years of age. Average life expectancy is 30-40 years.
The Silvery Gibbon Project is a not for profit organization based in Perth, Western Australia. The project was established in 1991 and works to raise awareness for this endangered small ape. The project funds the Javan Gibbon Centre, a rescue and rehabilitation facility in Java, Indonesia. Silvery Gibbon Project has also assisted with a reintroduction program as well as education and capacity building initiatives in Indonesia.
- www.iucnredlist.org IUCN Red List (April, 2011)
- MacDonald D (2001) The New Encyclopedia of Mammals. Oxford University Press, London.
- Primate Info Net (March, 2003)
- Kim S, Lappan S, Choe J C (2010) Diet and ranging behavior of the endangered Javan gibbon (Hylobates moloch) in a submontane tropical rainforest. Seoul National University, Seoul, Republic of Korea.
- Silvery Gibbon Project www.silvery.org.au
The Zoo and Aquarium Association acknowledges Perth Zoo for providing the factsheet information above and Clare Campbell for the photo.