Hylobates agilis, F. Cuvier, 1821
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publication ID |
https://doi.org/ 10.5281/zenodo.6727957 |
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DOI |
https://doi.org/10.5281/zenodo.6728285 |
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persistent identifier |
https://treatment.plazi.org/id/03D787BA-0E3B-FFC2-FF38-F57CF885C07F |
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treatment provided by |
Jonas |
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scientific name |
Hylobates agilis |
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Agile Gibbon
French: Gibbon agile / German: Schwarzhandgibbon / Spanish: Gibon gil
Other common names: Dark-handed Gibbon
Taxonomy. Hylobates agilis F. Cuvier, 1821 View in CoL ,
Indonesia, West Sumatra.
Some experts recognize two subspecies: agilis to the west and wunko to the east. In the Barisan Range of Sumatra, the pale morph is more common, while in the eastern lowlands and on the Malay Peninsula, the black morph predominates. Genetic data, however, do not support a division into subspecies. There is a small area of sympatry between this species and H. lar in northern Peninsular Malaysia, where both also hybridize, having been trapped on the “wrong” side of Lake Mudah when it was created by a hydroelectric dam in the late 1970s. It is sympatric with S. syndactylus in Sumatra. Monotypic.
Distribution. S Thailand (near the Malaysian border, E of the Thepha River watershed), N Peninsular Malaysia (from the Mudah and Thepha rivers in the N to the Perak and Kelantan rivers in the S), and most of Sumatra (from SE of Lake Toba and the Singkil River to the S). View Figure
Descriptive notes. There are no specific body measurements available; weight 5.7-5 kg (males) and 4.5-7.3 kg (females). The Agile Gibbon is sometimes called the darkhanded gibbon because its hands and feet are colored the same as the body or are somewhat darker. It is extremely variable in color, but it is not sexually dichromatic. Its coat may be either black (or maroon-brown) or pale (buff, gray, or creamy, with a darker ventral surface), and both sexes sport a white brow band. Adult males and juveniles have light (white or russet-white) cheek whiskers and a partial beard; females lose this at maturity. The crown hairis directed fanwise from the front of the scalp and is somewhat elongated over the ears.
Habitat. Semi-deciduous monsoon and tropical evergreen forest up to 1400 m above sea level. The Agile Gibbon is found at its highest densities in dipterocarp-dominated forest, but it also occurs in swamp and lowland forest to hill, submontane, and montane forest. It prefers the middle and upper canopy.
Food and Feeding. The Agile Gibbon is frugivorous, preferring fruits high in sugar, but it also eats immature leaves and insects—60% fruit, 39% young leaves, and 1% animal matter.
Breeding. Parental care by Agile Gibbons is predominantly given by the mother, although the father and elder siblings also assist. Weaning takes place at 18 months. Juveniles of both sexes reach adult size at aboutsix years of age, but they remain with their natal group until they reach sexual maturity at ¢.8-9 years. Individuals may live more than 30 years.
Activity patterns. Agile Gibbons are diurnal and arboreal, with much feeding and traveling early in the day. Both activities decline steadily throughout the day, and they settle for the night well before dusk.
Movements, Home range and Social organization. Average home range size was 29 ha for Agile Gibbons at Sungai Dal (Gunung Bubu Forest Reserve) on Peninsular Malaysia, with mean daily movements of 1339 m. Males are mainly responsible for defending the group’s territory from external threats such as humans. Females lead group's daily progressions and keep away other females, thereby preventing males from having more than one mate. Density estimates vary by population: 1-4-2-8 ind/km? in Bukit Barisan Seletan National Park, Sumatra; 6-11-4 ind/km? in Kerinci-Seblat National Park, Sumatra; and 5-5-18-9 ind/km® (2-5 groups/km?) in Sungai Dal. A density of 2 groups/km?* was estimated in parts of Hala Bala Wildlife Sanctuary, Thailand.
Status and Conservation. CITES Appendix I. Classified as Endangered on The IUCN Red List. The Agile Gibbon is protected by law in Indonesia, Malaysia, and Thailand. It is threatened mainly by loss of habitat due to logging, fires, spread of plantations (coffee, rubber, and other crops), and the illegal pet trade. It is especially threatened in the Sumatran part ofits distribution where it seems to be declining rapidly. On the mainland (Peninsular Malaysia and Thailand), there seem to be a number of stable populations, but their distributions have contracted. The Agile Gibbon is entirely confined to closed-canopy forest, and habitat conversion, road building, and fragmentation are increasing threats. It occurs in twelve protected areas: Batang Gadis, Berbak, Bukit Barisan Selatan, Bukit Duabelas, Bukit Tigapuluh, Kerinci-Seblat, Sembilang, Tesso Nilo, and Way Kambas national parks in Sumatra, Indonesia; Gunung Bubu, Belum-Temenggor, and Ulu Mudah forest reserves in Malaysia; and Hala Bala Wildlife Sanctuary in Thailand. Unfortunately, many of these protected areas are merely proposed, and their status is uncertain. Moreover, many of the Sumatran parks are in montane regions where Agile Gibbons only occur at low densities. In Bukit Barisan Selatan National Park in south-western Sumatra, populations are presently secure and healthy, but their continued survival depends on the Indonesian government regaining control over illegal deforestation in its parks. A population estimate over the whole range of the Agile Gibbon does not exist, but a 2002 assessment in Bukit Barisan Selatan calculated a population of 4479 individuals. In Peninsular Malaysia, Belum-Temenggor and Ulu Mudah are strongholds. The population of Agile Gibbons in Thailand likely numbers only a few thousand individuals, located in about three forest fragments or reserves.
Bibliography. Chivers (1977, 1978, 1980, 1984, 2001), Frisch (1967), Geissmann & Nijman (2008a), Gittins (1979, 1980, 1982, 1983), Groves (2001), Haimoff (1984b), Haimoff & Gittins (1985), Hirai, Hayano et al. (2009), Hirai, Wijayanto et al. (2005), Kloss (1929), Marshall (1981), Marshall & Sugardjito (1986), Montagu (1950), O’Brien et al. (2004), Yanuar (2001).
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
