Symphalangus syndactylus

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA MAMMALIA PRIMATES HYLOBATIDAE

Scientific Name: Symphalangus syndactylus
Species Authority: (Raffles, 1821)
Common Name(s):
English Siamang
Synonym(s):
Hylobates syndactylus (Raffles, 1821)
Symphalangus continentis Thomas, 1908
Symphalangus gibbon (C. Miller, 1779)
Symphalangus subfossilis Hooijer, 1960
Symphalangus volzi (Pohl, 1911)
Taxonomic Notes: The mainland and Sumatran forms have been considered distinct subspecies. No subspecies are recognized by Groves (2005).

Assessment Information [top]

Red List Category & Criteria: Endangered A2cd ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Nijman, V. & Geissman, T.
Reviewer(s): Mittermeier, R.A. & Rylands, A.B. (Primate Red List Authority)
Justification:
Listed as Endangered as, there is reason to believe the species has declined by at least 50% over the past 40 years (three generations) due primarily to hunting for pet trade and continued rates of habitat loss (mainly as a result of expanding agriculture and road building). Although there has likely been 70-80% habitat loss of primary habitat within the past 50 years within the range of the species, this species is one of the most adaptable gibbons to habitat change. Although the species occurs in numerous protected areas and retains a number of viable populations, it could in future be considered Critically Endangered due to historic habitat loss, and should be closely monitored in the future.

Geographic Range [top]

Range Description:This species is found in Indonesia (Barisan Mountains of west-central Sumatra), Malaysia (mountains of the Malay Peninsula south of the Perak River), and a small area of southern peninsular Thailand (Chivers 1974; Khan, 1970; O'Brien et al. 2003; Treesucon and Tantithadapitak 1997). It may have formerly occurred on the island of Bangka (Indonesia) as well. Reports of this species from Myanmar are almost certainly erroneous.
Countries:
Native:
Indonesia (Sumatera); Malaysia (Peninsular Malaysia); Thailand
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population: In a study on this species in Bukit Barisan Selatan National Park, Sumatra, O'Brien et al. (2004) calculated an average group density of one group for every 2.23 km2, with an average group size of 3.9, and a population estimate of 22,390 individuals. Healthy populations persist at the southern limit of its range in Bukit Barisan Selatan National Park, and these populations should survive over the long-term if the park maintains its present forest area, and if illegal hunting and habitat degradation are stopped (O'Brien et al. 2004). While some populations of this species appear secure today, its future is uncertain and will depend on vastly improved conservation efforts, especially in Sumatra's remaining parks and protected areas (O'Brien et al. 2004). Population densities for this species range from 2.4 to 24.6 individuals/km2 (O'Brien et al. 2004).
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: This species lives in primary and secondary semi-deciduous and tropical evergreen forest. All levels of the canopy are used, although emergent trees are required for resting and sleeping. Siamangs occur at lower densities in secondary forest, but can persist in secondary areas. They range from the lowlands up to 1,500 m in elevation. During a short survey in southern Sumatra, siamangs appeared to be less sensitive to habitat degradation than sympatric agile gibbons, Hylobates agilis (Geissmann et al. 2006). Since Bukit Barisan Selatan National Park coffee plantations have no canopy, they provide no habitat for this species (O'Brien et al. 2004).

Though this species is primarily folivorous in mainland Asia (Chivers 1974; Raemaekers 1984), it is primarily frugivorous on Sumatra (Palombit 1992; West 1982), feeding mostly on figs (O'Brien et al. 2003). Palombit (1992) argues that these animals are flexible foragers, preferring fruit when available, but able to switch to leaves when necessary. Such flexibility may help reduce siamang vulnerability to habitat disturbance (O'Brien et al. 2003). Siamang are strictly arboreal, highly territorial, and primarily monogamous (Chivers 1974). Extra-pair copulations have been reported in Ketambe, Gunung Leuser National Park, Sumatra (Palombit 1994), and groups with more than one adult male have been reported in the Way Kambas National Park population, Sumatra (O'Brien et al. 2003; Lappan 2005, 2007). Home range has been recorded at 15-47 ha on the Malayan peninsula (Chivers 1974; Raemaekers 1977; MacKinnon and MacKinnon 1980), and dispersal distance is less than 3 km. O'Brien et al. (2003) found that monogamy and strict territoriality may limit the range of possible response to fire and other severe disturbances by this species.
Systems: Terrestrial

Threats [top]

Major Threat(s): This species is threatened by forest conversion and opportunistic collection for pet trade on Sumatra, where both of these threats extend to populations in national parks and protection forests (O'Brien et al. 2004). Between 1995 and 2000, almost 40% of the habitat for this species on Sumatra was damaged or destroyed by logging, road development (barrier and hunting) and conversion to agriculture or plantations (O'Brien unpubl. data). Legal logging seems to be accelerating in Sumatra (Geissmann et al. 2006). Forests, where they remain, are extremely fragmented. Coffee plantations present an increasing threat (O'Brien and Kinnaird 2003). The siamang is one of the most heavily traded gibbon species for illegal pet trade (V. Nijman pers. comm.).

Conservation Actions [top]

Conservation Actions: This species is protected throughout its range, both by local laws as well as internationally through its listing on CITES Appendix I (O'Brien et al. 2004). It is known to occur in at least nine protected areas: Bukit Barisan National Park, Gunung Leuser National Park, Way Kambas National Park, West Langkat R (Indonesia); Fraser's Hill R, Gunong Besout Forest Reserve, Krau Wildlife Reserve, Ulu Gombak Wildlife Reserve (Malaysia); Hala Bala Wildlife Sanctuary (Thailand) (M. Richardson pers. comm.). There is a large worldwide captive population, in 96 collections.

Bibliography [top]

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Anonymous. 1971. Clear felling threatens the siamang. Oryx 11(1): 6-8.

Bennett, E., Davison, G. and Kavanagh, M. 1983. Social change in a family of siamang (Hylobates syndactylus). Malayan Nature Journal 36: 187-196.

Chivers, D. 1971. Spatial relations within the siamang group. In: H. Kummer (ed.), Proceedings of the 3rd International Congress of Primatology, Z├╝rich 1970, vol. 3: Behaviour, Basel and New York.

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Chivers, D. 1975. The behaviour of siamang in the Krau Game Reserve. Malayan Nature Journal 29: 7-22.

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Hunt Curtin, S. and Chivers, D. 1978. Leaf-eating primates of peninsular Malaysia: The siamang and the dusky leaf monkey. In: G. G. Montgomery (ed.), The ecology of arboreal folivores, Washington, DC, USA.

Kawabe, M. 1970. A preliminary study of the wild siamang gibbon, Hylobates syndactylus, at Fraser?s Hill, Malaysia. Primates 11(3): 285-291.

Khan, B. 1970. Distribution and population of siamang and gibbons in the state of Perak. Malayan Nature Journal 24: 3-8.

Lappan, S. 2005. Biparental care and male reproductive strategies in siamangs (Symphalangus syndactylus) in southern Sumatra. Ph.D. Thesis, New York University.

Lappan, S. 2007. Patterns of dispersal in Sumatran siamangs (Symphalangus syndactylus): Preliminary mtDNA evidence suggests more frequent male than female dispersal to adjacent groups. American Journal of Primatology 69: 692?698.

MacKinnon, J. and MacKinnon, K. 1980. Niche differentiation in a primate community. In: D. Chivers (ed.), Malayan forest primates: Ten years? study in tropical rain forest, pp. 167-190. Plenum Press, New York, USA.

Norikoshi, K. 1986. Socio-ecological study of siamangs in Maninjau, West Sumatra. Kyoto University overseas research report of studies on Asian non-human primates, vol. 5, Kyoto University, Kyoto, Japan.

Nurcahyo, A. 1998. Laporan penelitian studi perilaku harian siamang (Hylobates syndactylus) di Taman Nasional Bukit Barisan Selatan, Lampung. Jurusan Konservasi Sumberdaya Hutan. Universitas Gadjah Mada, Fakultas Kehutanan.

O'Brien, T. G. and Kinnaird, M. F. 2003. Caffeine and conservation. Science 300: 587.

O? Brien, T. G., Kinnaird, M. F., Nurcahyo, A., Iqbal, A. and Rusmanto, M. 2004. Abundance and distribution of sympatric gibbons in a threatened Sumatran rain forest. International Journal of Primatology 25(2): 267-284.

O? Brien, T., Kinnaird, M., Nurcahyo, A., Prasetyaningrum, M. and Iqbal, M. 2003. Fire, demography and the persistence of siamang (Symphalangus syndactylus: Hylobatidae) in a Sumatran rainforest. Animal Conservation 6: 115 - 121.

Palombit, R. 1992. Pair bonds and monogamy in wild siamang (Hylobates syndactylus) and white-handed gibbon (Hylobates lar) in northern Sumatra. Ph.D. Thesis, University of California.

Palombit, R. 1994. Extra-pair copulations in a monogamous ape. Animal Behaviour 47: 721 - 723.

Palombit, R. 1995. Longitudinal patterns of reproduction in wild female siamang (Hylobates syndactylus) and white-handed gibbons (Hylobates lar). International Journal of Primatology 16: 739-760.

Palombit, R. 1996. Pair bonds in monogamous apes: A comparison of the siamang Hylobates syndactylus and the white-handed gibbons. Hylobates lar Behaviour 133: 321-356.

Palombit, R. 1997. Inter- and intraspecific variation in the diets of sympatric siamang (Hylobates syndactylus) and lar gibbons (Hylobates lar). Folia Primatologica 68: 321-337.

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Raemaekers, J. 1980. Causes of variation between months in the distance travelled by gibbons. Folia Primatologica 34: 46-60.

Raemaekers, J. 1984. Large versus small gibbons: Relative roles of bioenergetics and competition in their ecological segregation in sympatry. In: H. Preuschoft, D. Chivers, W. Brockelman and N. Creel (eds), The lesser apes. Evolutionary and behavioural biology, Edinburgh.

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Treesucon, U. and Tantithadapitak, T. 1997. Siamang (Hylobates syndactylus): A new mammal recorded for Thailand. Natural History Bulletin of the Siam Society 45: 123-124.

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Citation: Nijman, V. & Geissman, T. 2008. Symphalangus syndactylus. In: The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 25 July 2014.
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