The silvery gibbon (''Hylobates moloch''), also known as the Javan gibbon, is a

primate Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians ( monkeys and apes, the latter includin ...

in the

gibbon Gibbons () are apes in the family Hylobatidae (). The family historically contained one genus, but now is split into four extant genera and 20 species. Gibbons live in subtropical and tropical rainforest from eastern Bangladesh to Northeast Indi ...

family Hylobatidae. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to the

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Gui ...

n island of

Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's mo ...

, where it inhabits undisturbed

rainforest Rainforests are characterized by a closed and continuous tree canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforest can be classified as tropical rainforest or temperate rainfores ...

s up to an altitude of . It is listed as

Endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and in ...

on the

IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biolo ...

since 2008, as the wild population is estimated at comprising less than 2500 mature individuals. Its coat is bluish-grey in colour, with a dark grey or black cap. Like all gibbons, the silvery gibbon lacks an external tail, has dorsally placed scapulae, and reduced flexibility in its lumbar region. It has long, curved fingers and very long forelimbs relative to its hind limbs. On average, it reaches in weight. It is diurnal and

arboreal Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. The habitats pose nu ...

, climbing trees skilfully and brachiating through the forests. Brachiation is possible because of its 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 gives birth to a single young, after a

gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pr ...

of seven months. 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

on the 2009

, 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. There are less than 2,000 silvery gibbons in the wild on eight sites that are considered to be genetically viable for the continuation of the species. There are also a dozen small, non-viable populations. Mount Halimun Salak National Park sustains the largest population of ca. 1,000 gibbons. Other large populations of several hundred are found in the

Gunung Ciremai National Park Mount Ciremai National Park is located around 50 km to the south of the city of Cirebon in West Java, Indonesia. The park extends into the Kuningan and Majalengka regencies south of Cirebon. The park surrounds Mt Ceremai, an active volcano, ...

and

Gunung Gede Pangrango National Park Mount Gede Pangrango National Park is a national park in West Java, Indonesia. The park is centred on two volcanoes—Mount Gede and Mount Pangrango—and is 150 km² in area. It evolved from already existing conservation areas, such as ...

. In the latter there is a Javan Gibbon Centre that rehabilitates ex-captive gibbons.The Silvery Gibbon Project
"Conservation Projects"
, retrieved 20 December 2013 Several zoos operate silvery gibbon breeding programs. Despite these efforts, the future survival of this species is in question.

Behaviour and ecology

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 majority of the solo song bouts or scream bouts are produced by the females. The female vocal bouts occur after 0500 hr, with the vocal bout activity peaking around 0600 hr. In contrast, the male vocal bouts primarily occur before 0500 hr. The males are usually very aggressive to others.

Classification

Some authors 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''

References

External links

*ARKive
images and movies of the Javan gibbon ''(Hylobates moloch)''
*http://www.gibbons.de {{Taxonbar, from=Q663728 silvery gibbon Fauna of Java Endemic fauna of Indonesia Endemic fauna of Java Primates of Indonesia Endangered fauna of Asia Species endangered by the pet trade silvery gibbon silvery gibbon