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
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
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.).
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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