View source for Siamang

{{Short description|Species of ape}}
{{Speciesbox
| name = Siamang<ref name=MSW3>{{MSW3 Primates|id= 12100785|page=181}}</ref>
| status = EN
| status_system = IUCN3.1
| status_ref = <ref name="iucn status 19 November 2021">{{cite iucn |author=Nijman, V. |author2=Geissmann, T. |author3=Traeholt, C. |author4=Roos, C. |author5=Nowak, M.G. |date=2020 |title=''Symphalangus syndactylus'' |volume=2020 |page=e.T39779A17967873 |doi=10.2305/IUCN.UK.2020-2.RLTS.T39779A17967873.en |access-date=19 November 2021}}</ref>
| status2 = CITES_A1
| status2_system = CITES
| status2_ref = <ref>{{Cite web|title=Appendices {{!}} CITES|url=https://cites.org/eng/app/appendices.php|access-date=2022-01-14|website=cites.org}}</ref>
| image = Siamang Tierpark Hellabrunn-4.jpg
| fossil_range = Middle [[Pleistocene]]-[[Holocene|Present]]<ref name=Suraprasit2016>{{cite journal|author=K. Suraprasit, J.-J. Jaegar, Y. Chaimanee, O. Chavasseau, C. Yamee, P. Tian, and S. Panha|title=The Middle Pleistocene vertebrate fauna from Khok Sung (Nakhon Ratchasima, Thailand): biochronological and paleobiogeographical implications|journal=ZooKeys|date=2016|issue=613 |pages=1–157|doi=10.3897/zookeys.613.8309|pmid=27667928 |pmc=5027644 |doi-access=free |bibcode=2016ZooK..613....1S }}</ref>
| genus = Symphalangus
| parent_authority = [[Gloger]], 1841
| species = syndactylus
| authority = ([[Thomas Stamford Raffles|Raffles]], 1821)
| range_map = Distribución symphalangus.png
| range_map_caption = Distribution of the siamang
}}
[[File:Siamang mid song.jpg|thumb]]
The '''siamang''' ({{IPAc-en|"|s|i:|@|m|{|N}}, {{small|also}} {{IPAc-en|UK|"|s|aI|@|-}};<ref>{{cite dictionary|dictionary=[[Lexico]]|title=siamang|url=https://www.lexico.com/definition/siamang|access-date=2022-04-26|archive-date=2022-04-26|archive-url=https://web.archive.org/web/20220426194648/https://www.lexico.com/definition/siamang|url-status=dead}}</ref><ref>{{Cite web|title=Definition of siamang {{!}} Dictionary.com|url=https://www.dictionary.com/browse/siamang|access-date=2022-02-14|website=www.dictionary.com|language=en}}</ref> '''''Symphalangus syndactylus''''') is an endangered [[arboreal]], black-furred [[gibbon]] native to the forests of [[Indonesia]], [[Malaysia]], and [[Thailand]]. The largest of the gibbons, the siamang can be twice the size of other gibbons, reaching {{cvt|1|m|ft|abbr=on}} in height, and weighing up to {{cvt|14|kg|lb|abbr=on}}. It is the only species in the genus '''''Symphalangus'''''. Fossils of siamangs date back to the [[Middle Pleistocene]].<ref name=Suraprasit2016/>
Two features distinguish the siamang from other gibbons. First, two digits on each foot—the second and third toes—are partially joined by a membrane, hence the [[species|specific]] name ''[[Syndactyly|syndactylus]]'', from the [[Ancient Greek]] σύν, ''sun-'', "with" + δάκτυλος, ''daktulos'', "finger". Second, a large [[gular sac]] (throat pouch), found in both males and females of the species, can be inflated to the size of the siamang's head, allowing it to make resonating calls.
Two [[subspecies]] of the siamang  are the nominate [[Sumatra]]n siamang (''S. s. syndactylus'') and the Malaysian siamang (''S. s. continentis'', in [[Malay Peninsula]]).<ref name=Geissmann>{{cite web | last = Geissmann | first = Thomas | title = Gibbon Systematics and Species Identification | url = http://gibbons.de/main/system/intro.html | access-date = 2006-04-13}}</ref> Otherwise, the Malaysian individuals are only a population. The siamang occurs [[sympatrically]] with other gibbons; its two ranges are entirely within the combined ranges of the [[agile gibbon]] and the [[lar gibbon]].
The siamang can live to around 40 years in captivity.<ref>Gron KJ. 2008 May 20. Primate Factsheets: Siamang (Symphalangus syndactylus) Taxonomy, Morphology, & Ecology . http://pin.primate.wisc.edu/factsheets/entry/siamang>. Accessed 2015 June 9.</ref>
While the illegal pet trade takes a toll on wild populations, the principal threat to the siamang is [[habitat loss]] in both [[Indonesia]] and [[Malaysia]]. The [[palm oil]] production industry is clearing large swaths of forest, reducing the habitat of the siamang, along with those of other species, such as the [[Sumatran tiger]].
== Description ==
[[File:Siamang Unkie SDZ CALVIN.jpg|thumb|A close-up of adult male's head]]
The siamang has long, dense, shaggy hair, which is the darkest shade of all gibbons. The ape's long, gangling arms are longer than its legs. The average length of a siamang is 90&nbsp;cm; the largest they have ever grown is 150&nbsp;cm. The face of this large gibbon is mostly hairless, apart from a thin mustache.
== Distribution and habitat ==
The siamang inhabits the forest remnants of [[Sumatra]] Island and the [[Malay Peninsula]], and is widely distributed from lowland forest to mountain forest—even rainforest—and can be found at altitudes up to 3800 m.<ref name="Rowe, Noel 1996">Rowe, Noel. (1996) "Pictorial Guide to the Living Primates" Charlestown, RI: Pagonia Press</ref> It lives in groups of up to six individuals (four individuals on average) with an average home range of 23 hectares.<ref name=OBrien1/><ref name=OBrien>{{cite journal | author = O'Brien, T. G. | author2 = M. F. Kinnaird | author3 = A. Nurcahyo | author4 = M. Prasetyaningrum| author5 = Dan M. Iqbal | year = 2003 | title = Fire, demography and persistence of siamangs (Symphalangus syndactylus: Hylobatidae) in a Sumatran rainforest | journal = Animal Conservation | volume = 6 | issue = 2 | pages = 115 | doi = 10.1017/S1367943003003159| s2cid = 86035086 }}</ref> Their day ranges are substantially smaller than those of sympatric ''[[Hylobates]]'' species, often less than 1&nbsp;km.<ref name="Rowe, Noel 1996"/> The siamang's melodious singing breaks the forest's silence in the early morning after the agile gibbons' or lar gibbons' calls. The siamangs in [[Sumatra]] and the [[Malay Peninsula]] are similar in appearance, but some behaviors differ between the two populations.
== Ecology and behavior ==
Siamangs have an ecology and relationship between two types of gibbons that share the same habitat. Those include the Agile gibbon and Lar gibbon. Both of the gibbons that live with the siamangs are Hylobates rather than Symphalangus. When two siamangs meet, they often have a bond with each other. They might also communicate by using their throat pouches and shouts to communicate when they feel excited, relaxed, trying to mate, or threatened. If siamangs use loud sounds, they also use body language to communicate. They use sign language or pointing to make others aware of what they need or what they want to do.
=== Diet ===
The siamang eats mainly various parts of plants. The Sumatran siamang is more [[frugivorous]] than its Malayan relative, with fruit making up to 60% of its diet. The siamang eats at least 160 species of plants, from [[vine]]s to woody plants. Its major food source is figs (''[[Ficus]]'' spp.).<ref name=OBrien/><ref name=Nurcahyo>Nurcahyo, A. (2001). Daily Ranging, Home-Range, Foods, Feeding and Calling in Siamang (Hylobates syndactylus). In WCS-IP 2001. Bukit Barisan Selatan National Park in Space and Time. 2000 -2001 Research Report. WCS-IP/ PHKA, Bogor. 35–52. (In Indonesian)</ref> The siamang prefers to eat ripe rather than unripe fruit, and young rather than old leaves. It eats flowers and a few animals, mostly insects. When the siamang eats large flowers, it eats only the [[petal#Corolla|corolla]]e (petals), but it eats all parts of smaller flowers, with the small fruit collected in its hand before being consumed. When it eats big and hard seeds or seeds with sharp edges, it peels out the fruit flesh and throws away the seed.<ref name=Nurcahyo/> Although its diet consists of substantial portions of fruit, it is the most [[folivorous]] of all members of [[gibbon|Hylobatidae]].<ref name="Rowe, Noel 1996"/> As it is also the largest gibbon, it fits well with the general primate dietary trend in which larger primates tend to be more folivorous.<ref>Fleagle J. G. (1988).  Size and Adaptation in Primates.  In Jungers WL (ed).  "Size and Scaling in Primate Biology".  New York: Plenum Press.</ref>
=== Demography and population ===
A group of siamangs normally consists of an adult dominant male, an adult dominant female, with offspring, infants, and sometimes a subadult. The subadult usually leaves the group after attaining the age of 6–8 years; subadult females tend to leave the group earlier than subadult males. Siamang gestation period is between 6.2 and 7.9 months; after the infant is born, the mother takes care of the infant for the first year of its life.<ref name="Lappan, Susan">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.</ref> Siamang males tend to offer more paternal care than do other members of the family Hylobatidae, taking up a major role in carrying an infant after it is about 8 months old.<ref name="Rowe, Noel 1996"/> The infant typically returns to its mother to sleep and nurse. The infant begins to travel independently from its parents by its third year of life.<ref name = "Chivers"/>
Siamangs are generally known to have monogamous mating pairs, which have been documented to spend more time in close proximity to each other, in comparison to other gibbon species.<ref>Palombit, Ryne A. (1996). “Pair Bonds in Monogamous Apes: A Comparison of the Siamang, Hylobates syndactylus, and the White-Handed Gibbon Hylobates lar. Behaviour. 133 (5) 321-356.</ref> Both monogamous and polyandrous groups, though, are found in [[South Sumatra]].<ref name ="Lappan, Susan"/> In studying these populations, infants belonging to monogamous groups were found to receive more overall male care than infants in the polyandrous groups. This reduced care is most likely due to reduced certainty of paternity in these groups.<ref name ="Lappan, Susan"/>
Habitat disturbance affects siamang group composition; it is varied in age-sex structure between intact forest and burnt, regrown forest. The burnt, regrown forest population contained more adult and subadults than the intact forest population, which had more infants, small juveniles, and large juveniles. Infant survival rates in burnt, regrown forest groups are lower than in intact forest groups. The number of individuals in the latter is higher than in the former.<ref name=OBrien/> The siamang in disturbed forests live in small groups and have a density lower than in intact forests because of lack of food resources and trees for living.
In the 1980s, the [[Indonesia]]n population of the siamang in the wild was estimated to be 360,000 individuals.<ref name=Nijman/> This figure may be less in the 21st century: [[Bukit Barisan Selatan National Park]] is the third-largest protected area ({{convert|3568|km2|disp=or|abbr=on}}) in [[Sumatra]], of which roughly {{convert|2570|km2|abbr=on}} remain under forest cover inhabited by 22,390 siamangs (in 2002 censuses). In [[Sumatra]], the siamang prefers to inhabit lowland forest between {{convert|500|and|1000|m|abbr=on}} above sea level.<ref name=OBrien1/>
=== Behavior ===
The siamang tends to rest for more than half of its waking period from dawn to dusk, followed by feeding, moving, foraging, and social activities. It takes more rest during midday, taking time to groom others or to play. During resting time, it usually uses a branch of a large tree, lying on its back or belly. Feeding behaviors, foraging, and moving are most often in the morning and after resting. Grooming is one of the most important social interactions among family members. Grooming takes place between adults earlier in the day; the adults groom the juveniles later in the day. Adult males are the most involved in grooming.<ref name = Chivers/>
[[Image:DPPP 5348.jpg|thumb|240px| A siamang group at rest in [[Sumatra]], [[Indonesia]] - siamangs rest up to 50% of their waking hours.]]
In the dry season, the size of the siamang's daily range is larger than in the rainy season. The siamang in [[South Sumatra|southern Sumatra]] spends less time foraging than siamangs in other places, as it eats a diet higher in fruit. It thus  consumes more nutrients, which results in less time needed for food acquisition. A siamang may spend an entire day in a single fruiting tree, moving out when it wants to rest and returning to feed.<ref name=Nurcahyo/>
Siamangs are a very social species of primates and exhibit a variety of tactile and visual gestures, along with actions and facial expressions to communicate and increase social bonds within their family group.<ref>Liebal, Pika, and Tomasello. (2004). “Social Communication in Siamangs (Symphalangus syndactylus): use of gestures and facial expressions” Primates. 45(1): 41-57.</ref> They are also territorial, and interact with other family groups by making loud calls to let other groups know where their territory is. The calls may be asynchronous, where they are not directed at a particular neighbouring group, or simultaneous group calls may take place across the territory boundary. Males are known to chase one another across the boundary.<ref name = Chivers/>
{{anchor|Copulation}}
Grooming frequency between males and females has been found to correlate to copulation frequency, as well as bouts of aggression. Pairs copulate over four to five months at intervals of two to three years. The peak of their reproductive activity is often during the time when fruit is most abundant.<ref name = Chivers/> Dorsoventral copulation is the most common type in siamangs, where the female is squatting and the male hangs by his arms and grips the female with his legs, whereas ventroventral copulation, where both primates are suspended, occurs only one in 60 times on average.<ref name = Chivers>[https://www.jstor.org/discover/10.2307/4533736?uid=3739912&uid=2&uid=4&uid=3739256&sid=47698812092497  Chivers, David J. (1976). Communication within and between family groups of siamang (''Symphalangus syndactylus''). Behaviour 57 (1-2): 116-135.]</ref>
=== Role of calling ===
[[File:Symphalangus syndactylus 4zz.jpg|thumb|Siamang calling with throat sac inflated]]
[[File:Symphalangus syndactylus 20170623 Doué-la-Fontaine.ogg|thumb|Siamangs' call]]
[[File:Black-gibbons-sumatra-2022.ogg|thumb|Siamang, Sumatra, 2022]]
The siamang starts its day by calling in the early morning; it calls less after midday, with the peak of the calls around 9:00 to 10:00 am. Most of the siamang's calls are directed to its neighbours rather than to those inside its home range. This means the siamang's calling is in response to disturbances and to defend its territory. Calls in the late morning typically happen when it meets or sees another siamang group. The edge of the siamang's home range, which may overlap another, is often the place where calling is made. Counter (co-response) calling occasionally happens near the border or in the overlap area. Calls are numerous when fruit is more abundant rather than when it is less available. Branch shaking, swinging, and moving around the tree crowns accompany the calling. This movement might be to show the other groups where they are.
The siamang prefers calling in the living, tall, and big trees, possibly where another group is easy to see. Besides that, such trees can support siamang movement. Calling trees are usually near feeding trees, but sometimes they call in the feeding trees.<ref name=Nurcahyo/><ref name=Kinnaird1>{{cite journal | author = Kinnaird, M. F. | author2 = O’Brien, T. G. | author3 = Nurcahyo, A. | author4 = Prasetyaningrum, M. | name-list-style = amp | year = 2002 | title = Intergroup spacing and the role of calling among siamangs | journal = Proceedings of the XIX Congress of the International Primatological Society (Abstract)}}</ref>
Mated pairs produce loud, well-patterned calling bouts, which are referred to as duetting. These calls advertise the presence and status of a mated pair.<ref name = Geissmann/> Newly formed pairs spend more time singing than an established pair. Advertising the presence of a strong bond is advantageous in territorial defense.<ref>{{cite journal|last=Geissmann|first=Thomas|title=Mate Change Enhances Duetting Activity in the Siamang Gibbon (Hylobates syndactylus)|journal=Behaviour|year=1986|volume=1|issue=96|pages=17–27|doi=10.1163/156853986x00199}}</ref> Siamang duetting differs from other species because it has a particularly complex vocal structure. Four distinct classes of vocalizations have been documented: booms, barks, ululating screams, and bitonal screams. Females typically produce long barks and males generally produce bitonal screams, but both sexes have been known to produce all four classes of vocalizations.<ref>{{cite journal|last=Geissmann|first=Thomas|title=Duet Songs of the Siamang, Hylobates Syndactylus: II. Testing the Pair-Bonding Hypothesis during a Partner Exchange|journal=Behaviour|year=1999|volume=8|issue=136|pages=1005–1039|doi=10.1163/156853999501694|s2cid=54736136}}</ref> Unlike other gibbons in which vocalization is added by laterally expanded [[Laryngeal saccules|laryngeal sacs]], those in siamangs fuse with each other and extend into the ventral area of the neck.<ref name="Koda Nishimura Tokuda Oyakawa 2012 pp. 347–355">{{cite journal |last1=Koda |first1=Hiroki |last2=Nishimura |first2=Takeshi |last3=Tokuda |first3=Isao T. |last4=Oyakawa |first4=Chisako |last5=Nihonmatsu |first5=Toshikuni |last6=Masataka |first6=Nobuo |date=2012 |title=Soprano singing in gibbons |journal=American Journal of Physical Anthropology |volume=149 |issue=3 |pages=347–355 |doi=10.1002/ajpa.22124 |pmid=22926979 |issn=0002-9483}}</ref>
=== Seeding ===
As a frugivorous animal, the siamang disperses seeds through defecation as it travels across its territory. The siamang can carry seed while digesting, and defecate between {{cvt|81.9|and|365.9|m}} from the seed resource, which supports the forest's regeneration and [[Ecological succession|succession]].<ref name=Rusmanto>{{cite journal |last1=Adyn |first1=M.F. |last2=Sibarani |first2=M.C. |last3=Utoyo |first3=L. |last4=Surya |first4=R.A. |last5=Sedayu |first5=A. |title=Role of siamang (Symphalangus syndactylus) as seed dispersal agent in a Sumatran lowland tropical forest |journal=Biodiversitas | issn=1412-033X |volume=23 |issue=4 |date=April 2022 |pages=2101–2110 |doi=10.13057/biodiv/d230445|s2cid=248447919 |doi-access=free }}</ref>
==Threats and conservation==
As an arboreal primate whose survival absolutely depends on the forest, the siamang faces [[population pressure]] due to habitat loss,<ref name=OBrien1>{{cite journal | author = O'Brien, T.G. | author2 = M.F. Kinnaird | author3 = A. Nurcahyo | author4 = M. Iqbal | author5 = M. Rusmanto | name-list-style = amp | year = 2004 | title = Abundance and Distribution of Sympatric Gibbons in a Threatened Sumatran Rainforest | journal = International Journal of Primatology | volume = 25 | issue = 2 | pages = 267–284 | doi = 10.1023/B:IJOP.0000019152.83883.1c| s2cid = 32472118 }}</ref> [[poaching]], and hunting.<ref name=Nijman>Nijman, V. (2005). In Full Swing: An Assessment of Trade in Orang-Utans and Gibbons on Java and Bali, Indonesia. A Traffict Southeast Asia Report. Traffic Southeast Asia</ref><ref name=Nursahid>Nursahid, R. and Bakdiantoro, H. (2005). Illegal Primate Trade in Indonesia. Profauna Indonesia. Presentation in SEAPA 1st Congress.</ref>
===Habitat loss===
[[Image:Siamang Hellabrunn 2004.jpg|thumb|240px|Siamang, [[Tierpark Hellabrunn]], Munich, Germany]]
A major threat to the siamang is [[habitat fragmentation]] due to [[plantation]]s, [[forest fire]], [[illegal logging]], [[wikt:encroachment|encroachment]], and human development. Firstly, palm-oil plantations have removed large areas of the siamang's habitat in recent decades. Since 2002, 107,000&nbsp;km<sup>2</sup> of [[oil palm]] have been planted,<ref name=Palmer>Palmer, C. E. The Extent and Causes of Illegal Logging: An Analysis of a Major Cause of Tropical Deforestation in Indonesia. CSERGE Working Paper.</ref> which has replaced much rainforest in [[Indonesia]] and [[Malaysia]], where the siamang originally lived. Secondly, in the second decade of the 21st century, forests in the [[Malay Peninsula]] have been destroyed due to illegal logging. Sixteen out of the 37 permanent forest reserves in [[Kelantan]], in the Malay Peninsula, where most of the siamangs live, have been encroached upon by illegal loggers.<ref>{{cite web |url=https://www.malaymail.com/amp/news/malaysia/2020/12/07/illegal-logging-detected-in-16-kelantan-forest-reserves/1929666 |title= Illegal logging detected in 16 Kelantan forest reserves|author=<!--Not stated--> |date=7 December 2020 |website= malaymail.com|publisher=Malay Mail |access-date= 17 January 2021|quote=}}</ref> Thirdly, forest encroachments change forest cover into cultivated land; for example, the rising price of coffee in 1998 encouraged people in [[Sumatra]] to replace the forest with coffee plantations.<ref name=Kinnaird>{{cite journal | author = Kinnaird, M.F. | author2 = Sanderson, E.W. | author3 = O'Brien, T.G. | author4 = Wibisono, H.T. | author5 = Woolmer, G. | name-list-style = amp | year = 2003 | title = Deforestation trends in a tropical landscape and implications for endangered mammals | journal = Conservation Biology | volume = 17 | pages = 245–257 | doi = 10.1046/j.1523-1739.2003.02040.x| s2cid = 59583614 }}</ref> Fourthly, development in many areas requires infrastructure, such as roads, which now divide conservation areas and have caused forest fragmentation and [[edge effect]]s.
=== Poaching and hunting ===
Unlike other parts of Asia, primates are not hunted for their meat in Indonesia. They are hunted for the [[Wildlife smuggling|illegal pet trade]], with hunters preferring infant siamangs. Poachers often kill the mothers first, since siamang females are highly protective of their infants, and removing the infant without first killing the mother requires more effort. Most siamangs on the market are infants, which often die during transportation.<ref name=Nijman/><ref name=Nursahid/>
===Conservation===
Siamang can be found in at least 11 protected areas:
;Indonesia
* [[Bukit Barisan Selatan National Park]]
* [[Gunung Leuser National Park]]
* [[Kerinci Seblat National Park]]
* [[Langkat Barat Wildlife Reserve]]
* [[Way Kambas National Park]]
;Malaysia
* [[Fraser's Hill Reserve]]
* [[Gunong Besout Forest Reserve]]
* [[Krau Wildlife Reserve]]
* [[Ulu Gombak Wildlife Reserve]]
;Thailand
* [[Hala Bala Wildlife Sanctuary]]<ref name="iucn status 19 November 2021" />
==References==
{{Reflist|2}}
==External links==
{{Commons|Symphalangus syndactylus|Siamang}}
{{Wikispecies|Symphalangus}}
{{Wikispecies|Symphalangus syndactylus|Siamang}}
*[http://www.gibbons.de/main/index.html Siamang photos]
*[http://www.gibbons.de/main/sound/12synd.html Siamang songs]
*[http://www.gibboncenter.org/ Gibbon Conservation Center]
*[http://pin.primate.wisc.edu/factsheets/entry/siamang Primate Info Net ''Symphalangus syndactylus'' Factsheet]
*http://www.sandiegozoo.org/animalbytes/t-siamang.html
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{{Haplorhini|Ho.}}
{{Taxonbar|from1=Q1962797|from2=Q213889|from3=Q41167995|from4=Q46679442}}
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[[Category:Gibbons]]
[[Category:Fauna of Sumatra]]
[[Category:Fauna of Southeast Asia]]
[[Category:Mammals of Indonesia]]
[[Category:Mammals of Malaysia]]
[[Category:Mammals of Thailand]]
[[Category:Primates of Southeast Asia]]
[[Category:Primates of Indonesia]]
[[Category:Species endangered by the pet trade]]
[[Category:Mammals described in 1821]]
[[Category:Taxa named by Thomas Stamford Raffles]]