Animal Info - Silvery Gibbon

(Other Names: Grey, Javan or Moloch Gibbon; Gibbon Cendré; Gibón Ceniciento; Moloch; Wauwau)

Hylobates moloch (H. lar m.)

Status: Critically Endangered


Contents

1. Profile (Picture)
2. Status and Trends (IUCN Status, Countries Where Currently Found, Population Estimates, History of Distribution, Threats and Reasons for Decline)
3. Data on Biology and Ecology (Weight, Habitat, Gestation Period, Birth Rate, Diet, Behavior, Social Organization, Density and Range)
4. References


Profile

Pictures: Silvery Gibbon #1 (7 Kb JPEG) (Kids Ecol. Corps); Silvery Gibbon #2 (20 Kb JPEG) (Gibbon Research Lab)

The silvery gibbon weighs about 6 kg (13 lb). It is found in lowland, hill and montane forests and eats mostly fruit and leaves.. In the Dieng Mountains of central Java, its habitat consisted of secondary forest with a rather dense and close canopy, and undisturbed primary forest. All gibbons are arboreal and diurnal. The silvery gibbon appears to prefer the taller trees for resting, foraging and locomotion. In a study in the Dieng Mountains of central Java, gibbons were seen on three occasions: a single adult, two adults and a group of seven. An average group size of 3.3 individuals has been reported.

The silvery gibbon is endemic to the western half of Java, Indonesia. Most populations can be found in the western province, but a few remain in central Java. It has declined and continues to be threatened due to habitat loss because of expanding human populations on Java. Only 4% of its original habitat remains. Remaining populations occur in about 20 forested areas mainly scattered over West Java. 


Status and Trends

IUCN Status:

Countries Where the Silvery Gibbon Is Currently Found:

2004: Occurs in Indonesia (Java) (IUCN 2004).

Population Estimates:

[Note: Figures given are for wild populations only.]

History of Distribution:

The silvery gibbon is endemic to the western half of Java, Indonesia. Most populations can be found in the western province, but a few remain in central Java (Nijman & van Balen 1998). They occur in about 20 forested areas mainly scattered over West Java. Many of these smaller populations are considered non-viable in the long term. Although recent discoveries show that the Central Javan population may be larger than previously assumed, population estimates still suggest that intervention will be necessary in order to conserve the species. (Gates 2002)

Threats and Reasons for Decline:

The silvery gibbon has declined and continues to be threatened due to habitat loss because of expanding human populations on Java. Only 4% of its original habitat remains (Kool 1992).


Data on Biology and Ecology

Weight:

The silvery gibbon weighs about 6 kg (13 lb).

Habitat:

The silvery gibbon is found in lowland, hill and montane forests. In the Dieng Mountains of central Java, its habitat consisted of secondary forest with a rather dense and close canopy, and undisturbed primary forest. Although 1600 m is considered to be the upper limit of the species, it has been reported from altitudes up to 2400'. (Kool 1992; Nijman & van Balen 1998)

The silvery gibbon is one of the species that live in the Sundaland Biodiversity Hotspot (Cons. Intl.).

Gestation Period:

7 - 8 months.

Birth Rate:

A single young is usually born. There are 2 - 3 years between births.

Diet:

The silvery gibbon eats mostly fruit and some leaves.

Behavior:

All gibbons are arboreal and diurnal. The silvery gibbon appears to prefer the taller trees for resting, foraging and locomotion.

Social Organization:

In a study in the Dieng Mountains of central Java, gibbons were seen on three occasions: a single adult, two adults and a group of seven (Nijman & van Balen 1998). An average group size of 3.3 individuals has been reported (Kappeler 1984b cited in Kool 1992).

Density and Range:

Density:

  • In a study of the silvery gibbon in Gunung Halimun Reserve in western Java, a group density of 2.6 groups/sq km (6.8 groups/sq mi) was derived. Using a reported average group size of 3.3 individuals/group (Kappeler 1984b cited in Kool 1992), density, within the altitudinal range censused in Gunung Halimun (700 - 1075 m (2300 - 3500')), was determined as 8.6 individuals/sq km (22 individuals/sq mi). This is higher than a previous estimate of 2-7 individuals/sq km (5 - 20 individuals/sq mi) for hill rain forest (500-1000 m altitude (1600 - 3300' altitude)) (Kappeler 1984a cited in Kool 1992). At higher elevations, the density of the silvery gibbon is lower and has been estimated at 1-3 individuals/sq km (3 - 8 individuals/sq mi) for lower montane forest (Kappeler 1984a cited in Kool 1992). (Kool 1992)
  • In a study in the Dieng Mountains of central Java, assuming the same reported average group size of 3.3 individuals/group as mentioned above (Kappeler 1984b cited in Kool 1992), the density of silvery gibbons was estimated to be 3.0 - 3.6 individuals/sq km (7.8 - 9.4 individuals/sq mi) (Nijman & van Balen 1998)

References

Aisquith 2001, Burton & Pearson 1987, Cons. Intl., Gates 2002, Gibbon Research Lab, IUCN 1994, IUCN 1996, IUCN 2000, IUCN 2003a, IUCN 2004, Kids Ecol. Corps, Kool 1992, Macdonald 1984, Nijman & van Balen 1998, Nowak & Paradiso 1983, Schuhmacher 1967


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Last modified: March 11, 2006;

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