Javan gibbon  (Hylobates moloch)

The silvery or Javan gibbon has long fluffy silver-grey fur (2), with darker markings on the chest and cap (4). It has long arms and legs, long fingers and reduced thumbs, all of which are adaptations for brachiation (swinging through the trees from arm to arm) (2). Males produce simple ‘hoot' calls, whilst the calls of females are more variable, ending in a ‘bubble'. (4). Both sexes also give a ‘scream' alarm call (8).

The silvery gibbon is endemic to the western half of the island of Java, Indonesia (3).

Inhabits tropical lowland, hill and montane (3) rainforests between sea level and 1500 meters (2). This species shows a preference for taller trees for resting, foraging and locomotion (3).

Gibbons are highly adapted for their arboreal lifestyle, feeding and sleeping in the trees; the long arms are used to throw themselves from tree to tree, easily covering gaps as wide as 10m (8). Males and females are monogamous, living in family groups with around 4 juvenile offspring who subsequently disperse (8). Group territories are actively defended by patrols, who engage in impressive bouts of loud calls and aggression (2).

The silvery gibbon has undergone a dramatic population decline principally as a result of habitat destruction (6), and also from the trapping of juveniles for the pet trade (2). The native forests of Java have been cleared for logging, agriculture and development, and the species has declined to fewer than 1000 individuals over then last 25 years (4). This gibbon appears to be on the very brink of extinction with only a handful of isolated viable populations remaining (6).

In light of the critical status of this species in the wild, a Javan gibbon rescue and rehabilitation workshop was conducted in 1997 hosted by Conservation International and the University of Indonesia (2). It was agreed that a rescue and rehabilitation centre was needed and education programmes were proposed (5). Currently, the only viable protected population is found within the Gunung Halimun National Park; if this attractive primate is to survive it is vital that protection both within the park and in other areas is increased (6).

For more information on the Javan gibbon see The Silvery Gibbon Project:
www.silvery.org.au

Authenticated by Dr David J. Chivers, University of Cambridge.