Common name: Siamang
The siamang (Symphalangus syndactylus) is listed as endangered primate species (Nijman et al 2008) due to continued rates of habitat loss and hunting for pet trade. This diurnal species is strictly arboreal and highly territorial, and is known for its impressive calls and brachiate movement through the trees. Distribute in Indonesia (Barisan Mountains of west-central Sumatra), Malaysia and Thailand. Siamang 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. It typically occurs at elevations between 305 and 1,220 meters.
The siamang has long, dense, shaggy black fur, apart from a grey area around the chin and mouth. Body size is often double the size of other gibbon species. Head and body length of the adult siamang is between 737-889 mm; female body weight is 10,0-11,1 kg in range, while adult male is between 12,3-14,8 kg (Rowe 1996). The most characteristic feature of the siamang is its large inflatable throat sac, which is sparsely haired (Marshall & Sugardjito 1986; Mootnick 2006). When fully inflated, the throat sac is comparable in size to the animal’s head (Papaioannou 1973). Other unique characteristic of the species is brachiation as part of locomotion. Types of locomotion include vertical climbing, swinging, jumping and arboreal bipedal. When compared to other gibbons, siamangs are slower in their movement and they rest by propping or draping themselves in the trees (Chivers 1972a). The species is a monogamous primate, lives in a family group, with up to three offspring. The siamang produces a single offspring at two to three year intervals. Gestation period is between 189-239 days and initially clings to its mother. Sub adult siamang will leave the family group searching for a mate. Life span of the species can be more than 40 years in captivity.
The diet composition of siamang consists of 49% fruit, 38% leaves, 3% flowers, and 10% insects. Up to 37% of the entire siamang diet is figs (Bartlett 2007). Siamangs eats mostly young leaves and only small amounts of mature leaves (Palombit 1992). Home range is about 15 to 35 hectares, most of which is defended as a territory.
Photo was taken by Entang Iskandar.
Bartlett TQ. 2007. The Hylobatidae: small apes of Asia. In: Campbell CJ, Fuentes A, MacKinnon KC, Panger M, Bearder SK, editors. Primates in perspective. New York: Oxford U Pr. p 274-89.
Chivers DJ. 1972a. The siamang and the gibbon in the Malay peninsula. Gibb Siam 1:103-35.
MacKinnon JR, MacKinnon KS. 1980. Niche differentiation in a primate community. In: Chivers DJ, editor. Malayan forest primates: ten years’ study in tropical rain forest. New York: Plenum Pr. p 167-90.
Marshall J, Sugardjito J. 1986. Gibbon systematics. In: Swindler DR, Erwin J, editors. Comparative primate biology, volume 1: systematics, evolution, and anatomy. New York: Alan R. Liss, Inc. p 137-86.
Mootnick AR. 2006. Gibbon (Hylobatidae) species identification recommended for rescue or breeding centers. Prim Conserv 21:103-38.
Nijman, V. & Geissman, T. 2008. Symphalangus syndactylus. The IUCN Red List of Threatened Species 2008: e.T39779A10266335.http://dx.doi.org/10.2305/IUCN.UK.2008.RLTS. T39779A10266335.en. Downloaded on 13 November 2015.
Palombit RA. 1992. Pair bonds and monogamy in wild siamang (Hylobates syndactylus) and wite-handed gibbon (Hylobates lar) in norther Sumatra. PhD dissertation, University of California, Davis. 453 p.
Papaioannou J. 1973. Observations on locomotor and general behaviour of the siamang. Malay Nat J 26:46-52.
Rowe N. 1996. The Pictorial Guide to the Living Primates. New York: Pogonian Press.