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SPECIES PROFILE
SIAMANG
Symphalangus syndactylus
December 2012
Compiled by
5.1 SUMMARY
Symphalangus syndactylus – The Siamang
The Siamang is a long sleek primate with long arms and legs. It is the largest of the lesser apes.
The Siamang is endangered throughout its range. Many of its threats come from humans
through activities such as the Pet Trade and forest degradation through clear felling and palm
oil plantation development. The Siamang has a decreasing trend in population throughout its
natural range. It is known for its brachiating between trees and its mid-morning and afternoon
song/call.
5.2 NAME AND TAXONOMY
Kingdom – Animalia
Phylum – Chordata
Class – Mammalia
Order – Primate
Family – Shylobatidae
Genus - Symphalangus
Species - syndactylus
Sub Species - S.s.syndactylus the Sumatran Siamang
- S.s.continentis the Malayan Siamang
Synonyms - Hylobates syndactylus (Raffles, 1821)
- Symphalangus continentis Thomas, 1908
- Symphalangus gibbon (C. Miller, 1779)
- Symphalangus subfossilis (Hooijer, 1960)
- Symphalangus volzi (Pohl,1911)
Taxomonic Notes - The mainland and Sumatran forms have been considered distinct
subspecies. No subspecies are recognised by Groves (2005).
Common Names – Siamang, Greater Gibbon.
Closest Relatives – Gibbons. Siamang and Gibbon make up the lesser apes family.
5.3 DESCRIPTION
Height (head and body length): 73.7 - 88.9cm. Reach over 1m tall when standing on their legs.
Weight - males average 11.9kg in the wild and 12.8kg in captivity.
- females average 10.7 in the wild and 10.5kg in captivity.
The Siamang is a long sleek primate reaching heights of 1 metre and weights of 14kg. They are
covered in black fur and have no tail. They have long arms which can span 1.5 – 1.8m wide.
Males have a prominent perpetual tuft of hair about 15 cm long.
The head is small and round. The face is essentially bare, with a flat broad nose with big
nostrils. The eyes are dark brown. The ears are hidden in the fur. There is a fairly large
laryngeal sac, which enhances the siamang’s call, helping make it the loudest of the gibbons.
The sac is hairless and puffs up when sounds are emitted.
Like in other gibbons, the siamang's arms are longer than their legs. Palms and fingers, except
for the short, opposable thumb, are elongated. Webbing of the second and third finger is a
constant feature and may extend to the terminal joint. Their feet have five toes. The big toe is
opposable too. Siamangs can grasp and carry things with both their hands and their feet.
Young are born about 410-600 g and are hairless except for a small tuft on top of the head.
There are no similarities between the Siamang and the native Australian species.
5.4 CONCERVATION AND LEGAL STATUS
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.).
IUCN Red List – Endangered.
VPC - previously listed Category 2, currently listed as serious.
There is a large worldwide captive population, in 96 collections.
It is estimated that in the 1980’s there was approximately 360,000 siamangs within its natural
range. In the past 40 years it is believed that there has been a population decrease of around
50%. There is no direct management strategies in place at this time through their natural
range.
5.5 LIFE HISTORY
Siamangs give birth after an average of 230 – 235 days (6.2 to 7.9mth range) gestation. The
young are born 410 – 600gms with some hair on their body which is sparse. Their mother looks
after and carries the young for approximately one year. Young are weaned between 18 – 24
months usually weighing between 2.5 – 3kg (www.waza.org).
The Siamang males tend to offer more paternal care than other lesser primates with him taking
a major role in carrying the young after approximately 8mths of age. The infant typically
returns to its mother for nursing and sleeping (Lappan 2008).
Infants travel independently of their parents from around the age of 3yrs. Sub adults remain
with the parental group till around 6 -8 years of age. Females tend to leave earlier than the
male (Chivers 1976).
Siamangs typically live in monogamous mating pairs consisting of an adult male and female
with their young usually infants but sometimes sub adults. Polyandrous groups have been
found in Sumatra usually in disturbed habitats (Lappan 2008).
Young reach sexual maturity at approximately 8 – 9yrs of age and it is around this time that
they will find a mate. The oldest recorded Siamang in captivity is 44yrs while many live to
around 40. Wild ages are less known but are expected to be lower.
5.6 HABITAT REQUIREMENTS AND PREFERENCES
The Siamang lives in primary and secondary semi-deciduous and tropical evergreen forest. All
levels of the canopy are used, although emergent trees are preferred 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.
The tropical hill forests are the primary habitat for the Siamang. In addition to the primary
lowland and hill forests they can also live in selectively logged primary freshwater swamp
forest, hill forests, and primary submontane forests. Siamangs are usually found at higher
levels of elevation than other lesser apes (Chivers 1977).
They are arboreal and very territorial having a home range of 0.2 - 0.48 sq km and a dispersal
distance of less than 3km (Chivers 1977).
They have a preference for fruit in their diet but will eat leafy vegetation if necessary.
They do not swim or engage in water activities, preferring to stay on the land up in the canopy.
The Siamang uses its long arms for swinging (brachiating) through the trees. This is their main
mode of locomotion.
They do not use hollow or fallen logs preferring to sleep in the higher canopy of trees. The
Siamang is not known for its nest building capabilities.
5.7 NATURAL GEOGRAPHIC RANGE
Symphalangus syndactylus is native to Indonesia (Sumatra), Malaysia (Peninsular Malaysia) and
Thailand.
In Indonesia the Siamang is found in the Barisan Mountains of West Central Sumatra, in
Malaysia the mountains of the Malay Peninsula south of Perak River and a small area of
Thailand’s Southern Peninsular (Chivers 1974; Khan, 1970; O’Brien et al. 2003; Treesucon and
Tantithadapitak 1997). It may have previously occurred on the island of Bangka (Indonesia) and
reports of the species in Myanmar are almost certainly erroneous (www.iucnredlist.org).
Map showing distribution of the Siamang
Symphalangus syndactylus
Green indicates range.
(map taken from http://pin.primate.wisc.edu/factsheets/entry/siamang/behav)
5.8 INTRODUCED GEOGRAPHIC RANGE
While the Siamang has been reintroduced into its natural range there is no evidence of
attempts to introduce it to an area outside that.
5.9 POTENTIAL DISTRIBUTION IN TASMANIA
Map showing climate matches where 10 is very similar and 0 is no match.
Tasmania has 9 matches total with all scores under 2. The rest of the state shows no match at
all.
5.10 DIET AND FEEDING BEHAVIOUR
On average, among several studies in both Malaysia and Indonesia, Siamangs eat a variety of
foods. This includes approximations of their diet distribution being 49% fruit (being between
32–61% of the diet), 38% leaves (17–58%), 3% flowers (1-9%) and 10% insects (1-12%) (Chivers
1974). Of the fruit Figs make up a significant proportion, up to 37% of a Siamangs diet (Bartlett
2007). Siamangs also have a preference for leaf types, eating mostly young leaves and only
small amounts of mature leaves. Over all more than 160 different species of plant are eaten.
Peaks in feeding occur over the course of the morning and decrease after that for the rest of
the day. (Chivers 1974, Chivers 1972a). They will spend approximately 34 -50% of their time
feeding throughout the day (Chivers 1976, Lappan 2005).
The Siamang utilises both its hands and feet to eat but is more likely to use its hands.
5.11 SOCIAL GROUPINGS
Siamangs typically live in monogamous mating pairs consisting of an adult male and female
with their young usually infants but sometimes sub adults. The sub adult tends to leave the
group between the ages of 6-8 years old. Females tend to leave the group earlier than males.
Polyandrous groups have been found in Sumatra usually in disturbed habitats (Lappan 2008).
5.12 NATURAL PREDATORS AND DISEASE
Due to its high position within the canopy and its quick, agile movement through the forest,
predation is not of great concern to the Siamang. However, a fully grown Siamang was once
found in the stomach of a python (Mille 2002).
Siamangs being primates are susceptible to zoonotic diseases. These include Hep B virus and
play host to intestinal parasites such as Taenia solium (tapeworm), Plasmodium falciparum
Causes Malaria) and Enterobius vermicularis (pin worm) (Keeling and Mc Clure 1972). The
common cold and flu are also known to affect Siamangs.
Humans pose the largest threat to the Siamang through forest degradation and poaching.
Forests are clear felled to make way for palm old plantations and Siamangs are the most
popular of the apes for the illegal pet trade.
5.13 THREATS TO HUMAN SAFETY
There are no reports of fatal attacks on humans by the Siamang. There are few reports of
hospitalisation after attacks by captive Siamangs on keepers and public during escapes. These
injuries are usually caused by the biting and grabbing from the Siamang. The attacks have not
been recorded frequently but these attacks often occur around the age of sexual maturity of
the Siamang (pers obs Shemwell 1996).
5.14 HISTORY AS A PEST
There is no record of the siamang being a pest throughout its natural range. This species has no
introduced range.
5.15 POTENTIAL IMPACT ON TASMANIA
There is little chance of the Siamang establishing in Tasmania. A very low climatch score was
recorded between the Siamangs natural habitat and Tasmania with all matches rating 2 or
below.
There is no record of Siamangs being an agricultural pest or having a negative impact on
human communities.
The species may be capable of damaging fruit crops such as apples.
5.16 PREVIOUS RISK ASSESSMENTS
Risk assessment for Australia resulted in the Siamang being given an establishment score of 5,
commodity damage score of 4 and risk to public safety score of 1.
VPC category – moderate.
SEWPaC lists siamang as eligible for non – commercial purpose only, excluding household pets.
5.17 RISK MANAGEMENT
The Siamangs will be transported in line with IATA standards during any movement outside the
grounds including this shipment from QLD.
The Siamangs will be housed in facilities which exceed both National Draft Standards and the
NSW EAPA.
Siamangs should be dealt with as hazardous animals. Work practices and husbandry routines
will reflect that. Keepers must be in sight and/or sound of another member of the work force.
Animal escape procedures will fall in line with those used at Taronga/WPZ as will recapture
plans.
Tasmania Zoo has staff with 13 years of Captive husbandry of Primates and has worked
specifically with Siamang and Gibbon in situ in Thailand Kra Bok Koo field station training local
staff, Cambodia as an advisor to the Wildlife Protection Office training staff and developing
primate facilities.
Operational procedures will be drawn up once facilities are near completion. All staff will also
be trained in the keeping system and use of the building as well as escape and recapture
procedure and any other relevant procedures required to house the Siamang. This will be
completed prior to animals arriving in Tasmania.
5.18 REFERENCES
Aldrich-Blake, F. and Chivers, D. 1973. On the genesis of a group of siamang. American Journal
of Physical Anthropology 38: 631-636.
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, Zürich 1970, vol. 3: Behaviour, Basel and New
York.
Chivers, D. 1971. The Malayan siamang. Malayan Nature Journal 24: 78-86.
Chivers, D. 1972. The siamang and the gibbon in the Malay Peninsula. In: D. Rumbaugh (ed.),
Gibbon and siamang, vol. 1, Basel and New York.
Chivers, D. 1974. The siamang in Malaya: a field study of a primate in tropical rain forest.
Contributions to Primatology 4: 1-335.
Chivers, D. 1975. Daily patterns of ranging and feeding in siamang. In: S. Kondo, M. Kawai and
A. Ehara (eds), Contemporary primatology. 5th International Congress of Primatology, Nagoya
1974, Basel and New York.
Chivers, D. 1975. The behaviour of siamang in the Krau Game Reserve. Malayan Nature Journal
29: 7-22.
Chivers, D. 1977. The feeding behaviour of siamang (Symphalangus syndactylus). In: T. H.
Clutton-Brock (ed.), Primate ecology: Studies of feeding and ranging behaviour in lemurs,
monkeys and apes, London, UK and New York, USA.
Chivers, D. 1979. The siamang and the gibbon in the Malay Peninsula. New York, USA.
Chivers, D. and Chivers, S. 1975. Events preceding and following the birth of a wild siamang.
Primates 16: 227-230.
Chivers, D. and Raemaekers, J. 1973. Behaviour of siamang. Malayan Nature Journal 26: 177.
Chivers, D., Raemaekers, J. and Aldrich-Blake, F. 1975. Long-term observations of siamang
behaviour. Folia Primatologica 23(1-2): 1-49.
Geissmann, T., Nijman, V. and Dallmann, R. 2006. The fate of diurnal primates in southern
Sumatra. Gibbon Journal 2: 18-24.
Gittins, S. and Raemaekers, J. 1980. Siamang, lar and agile gibbons. In: D. Chivers (ed.),
Malayan forest primates. Ten years study in tropical rain forest, pp. 63-105. Plenum Press, New
York, USA.
Groves, C. P. 2001. Primate taxonomy. Smithsonian Institution Press, Washington, DC, USA.
Groves, C. P. 2005. Order Primates. In: D. E. Wilson and D. M. Reeder (eds), Mammal Species of
the World, pp. 111-184. The Johns Hopkins University Press, Baltimore, Maryland, USA.
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.
Lappan, Susan. (2008). “Male Care of Infants in a Siamang (Symphalangus syndactylus)
Population including Socially Monogamous and Polyandrous Groups”. Behavioral Ecology and
Sociobiology. 62(8): 1307-1317.
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.
Mille, L.E. (2002) Eat or be Eaten. Predator Sensitive Foraging Among Primates. Cambridge
University Press, Cambridge.
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.
Raemaekers, J. 1977. Gibbons and trees: Comparative ecology of the siamang and lar gibbon.
Ph.D. Thesis, University of Cambridge.
Raemaekers, J. 1978. Changes through the day in the food choice of wild gibbons. Folia
Primatologica 30: 194-205.
Raemaekers, J. 1978. Competition for food between lesser apes. In: D. Chivers and J. Herbert
(eds), Recent advances in primatology, vol. 1: Behaviour, London, UK and New York, USA.
Raemaekers, J. 1978. The sharing of food sources between two gibbon species in the wild.
Malayan Nature Journal 31: 181-188.
Raemaekers, J. 1979. Ecology of sympatric gibbons. Folia Primatologica 31: 227-245.
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.
Raemaekers, J. and Chivers, D. 1980. Socio-ecology of Malayan forest primates. In: D. Chivers
(ed.), Malayan forest primates Ten years' study in tropical rain forest, New York, USA.
Shemwell ,C. 1996 Kra Bok Koo Primate Research and Rehabilitation Centre. Forestry Dept
Thailand.
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.
West, K. 1982. The ecology and behaviour of the Siamang (Hylobates syndactylus) in Sumatra.
M.Sc. Thesis, University of California.
en.wikipedia.org/wiki/Siamang
www.iucnredlist.org › Symphalangus syndactylus (Siamang)
www.waza.org