PIN welcomes primatologists who are working directly with species to send updates for our fact sheets any time, including sources. We also welcome all readers to send updates and sources for consideration: we will check with the experts before adding these updates. We advise readers to use our fact sheets as just one source of information and to always research additional sources.


Suborder: Haplorrhini
Infraorder: Simiiformes
Superfamily: Hominoidea
Family: Hylobatidae
Genus: Symphalangus
Species: S. syndactylus
Subspecies: S. s. syndactylus, S. s. continentis

Other names: Hylobates (Symphalangus) syndactylus, siamang, greater gibbon; S. s. syndactylus: Sumatran siamang; S. s. continentis: Malaysian siamang.

The taxonomic arrangement of siamangs has been modified by Groves (2005) and Mootnick & Groves (2005) who elevated the former subgenus Symphalangus to full generic level where it was formerly a subgenus of Hylobates.

Conservation status: please search the IUCN Red List.

Life span: >40 years (captive)
Total population: 200,000 (Sumatra)
Regions: Malay Peninsula, Sumatra
Gestation: 210 days (7 months)
Height: 73.7 to 88.9 cm (M & F)
Weight: 11.9 kg (M), 10.7 kg (F)


Siamang howling in a tree
Symphalangus syndactylus

Among the gibbons, the stocky siamangs are the largest (Mootnick 2006). The pelage is glossy black, the upper body has long hair and the chest is broad (Marshall & Sugardjito 1986; Mootnick 2006). The crown is flat and a white brow-band occurs at low levels (<5%) in captive and museum examples (Geissmann 1993; 2003). Perhaps the most characteristic feature of the siamang is its large inflatable throat sac, which is sparsely haired (Schultz 1933; Marshall & Sugardjito 1986; Mootnick 2006; A.Mootnick pers. comm.). When fully inflated, the throat sac is comparable in size to the animal’s head (Papaioannou 1973). Siamangs have no tail, as is the case in all of the lesser, or small, apes (Ankel-Simons 2000). However, males possess a downward directed genital tassel which can be as long as 13.5 cm (5.3 in) and resembles a tail (Marshall & Sugardjito 1986; Mootnick 2006). It is difficult to visibly tell the subspecies apart, although preliminary observations suggest that this might be possible based on nose morphology (Mootnick 2006). The second and third toes are connected by webbing which is variable in its extent, a condition that is reflected in the species’ scientific name (Schultz 1933; Marshall & Sugardjito 1986; Mootnick 2006). In addition, sometimes the fourth and fifth toes are also webbed (A. Mootnick & L. Theisen-Watt pers. obs. cited in Mootnick 2006).

There is some sexual dimorphism in siamangs, with males being somewhat larger than females (Wilson & Wilson 1976). In a small wild-shot sample, adult males averaged 11.9 kg (26.2 lb) and adult females averaged 10.7 kg (23.6 lb) (Geissmann 1993). In a much larger survey of captive individuals, adult males averaged 12.8 kg (28.2 lb) and adult females averaged 10.5 kg (23.1 lb) (Orgeldinger 1994). Head and body length ranges between 29 and 35 inches (73.7 and 88.9 cm) (Chivers 1985).

The predominant type of siamang locomotion is its characteristic brachiation, comprising around 80% of its movement (Chivers 1972b cited in Andrews & Groves 1976). This type of locomotion is extremely advantageous in the complex canopy environment for which the species is adapted (Bertram 2004). Other types of locomotion include vertical climbing, swinging, jumping and arboreal bipedal walking (Chivers 1972b cited in Andrews & Groves 1976; Papaioannou 1973). When compared to other gibbons, siamangs are slower in their movement and they rest by propping or draping themselves in the trees (Chivers 1972a).

In captivity, siamangs can live into their forties (Schmidt & Weigl 1999; Weigl 2005).


Symphalangus syndactylus

Siamangs are found on the island of Sumatra (Indonesia) and on the Malay (Malaysia and Thailand) peninsula (Treesucon 1997; Mootnick 2006). Each of the two locations has its own subspecies, with S. s. syndactylus being confined to Sumatra and S. s. continentis confined to the northwest and central Malay Peninsula (Mootnick 2006). Within the Malay peninsula, S. s. continentis is restricted in the east by the Pahang River, in the south by the Maur river and Tasek Bera, and in the north by the Perak river (Chivers 1980). There are no reports of occurrence east of the central range of the peninsula (Groves 1972). There is at least one report of siamangs from extreme southern Thailand, very near the border with Malaysia on the Malay peninsula in the Narathiwat Province (Treesucon 1997). On Sumatra, S. s. syndactylus occurs over most of the island but is mainly found in the west (MacKinnon 1984; Jenkins 1990).


The tropical hill forest is the primary habitat of the siamang. The species is most often found above 300 m (984.3 ft) in altitude, but can also live in lowland forests (Chivers 1977). In addition to primary lowland and hill forests, siamangs can also live in selectively logged primary freshwater swamp forests, selectively logged lowland forests, selectively logged hill forests and primary submontane forest (Wilson & Wilson 1976). Although sympatric with other gibbons in some habitats, siamangs occur more often at higher elevations than other gibbons (Wilson & Wilson 1976). However, the species is not commonly seen above 1500 m (4921.3 ft), although it may range as high as 1828.8 m (6000 ft) (Medway 1972; Caldecott 1980).

The seasons are not usually distinct in the tropical areas where the siamang lives (Chivers 1974). In southwestern Sumatra, in the Bukit Barisan Selatan National Park, rainfall is only weakly seasonal. Annually, it can be between 300 and 400 cm (118.1 and 157.5 in), amounts which are sometimes lower due to severe droughts. At this site, annual temperatures are usually between 22 and 35°C (71.6 and 95°F) but can be as high as 40°C (104°F) (O’Brien et al. 2003; 2004). On the Malay Peninsula, there is a time of increased rainfall around the beginning of each year with a following drier season which is accompanied by warmer temperatures. However, this cycle is variable between years (Chivers 1974). At the study site of Kuala Lompat, in the Krau Game Reserve in the Malay Peninsula during a two-year period, temperatures varied between 16.1 and 33.3°C (61 and 92°F). The wet season lasted roughly November-January, and the dry season between January-April (Chivers 1974).


On average, among several study sites in both Malaysia and Indonesia, siamangs eat a variety of foods, including 49% fruit (between 32-61% of the diet), 38% leaves (17-58%), 3% flowers (1-9%), and 10% insects (1-21%) (Papaioannou 1973; Chivers 1974; Raemaekers 1979; MacKinnon & MacKinnon 1980; Palombit 1992; 1997; Bartlett 2007). Of the fruit, figs can make up a significant percentage, up to 37% of the entire siamang diet (Bartlett 2007). Siamangs also have a preference of leaf types, eating mostly young leaves and only small amounts of mature leaves (Chivers 1974; Raemaekers 1979; MacKinnon & MacKinnon 1980; Palombit 1992). Overall, more than 160 different species of plant are eaten (T. O’Brien unpubl. data cited in O’Brien et al. 2003).

Symphalangus syndactylus

The daily activity period is usually over ten hours long (Chivers 1974; Raemaekers 1979). In general, siamangs awake around dawn and communally defecate shortly thereafter (Papaioannou 1973; Chivers 1974; Chivers et al. 1975). They will then feed or rest, depending on their proximity to food resources (Chivers 1972a). As to the daily pattern of activity, peaks in feeding occur over the course of the morning and decrease after that for the rest of the day (Papaioannou 1973; Chivers 1977). Resting increases over the day to a peak in the afternoon, and travel peaks in the morning (Chivers 1974). At night, siamang groups enter the highest branches of a single tree, high above the canopy but sometimes lower and in several trees (Chivers 1974; Gittins & Raemaekers 1980). Sleeping trees are often reused (Chivers 1974).

Daily time budgets vary between study sites, but traveling, resting and feeding typically are predominant activities (Lappan 2005). In Sumatra, male siamangs spend their time feeding (34.0%), resting (36.8%), traveling (16.8%), in social activities (5.2%) and in other activities (7.3%). Female siamangs spend their time feeding (37.3%), resting (33.8%), traveling (16.9%), in social activities (5.4%) and in other activities (7.3%) (Lappan 2005). Elsewhere in Sumatra during a different study, siamangs spent their time resting (44%), feeding and foraging (40%), traveling (12%), in intergroup interactions (3%) and singing (1%) (Palombit 1992; 1997). On the Malay peninsula, the day is spent feeding (50%), resting (25%), and traveling (22%), with grooming, singing and play each taking up about 1% of the day (Gittins & Raemaekers 1980). Among the group, there is a coordination of activities. In one study, all members of a group participated in the same activity over 60-75% of the day (Chivers 1976).

Home ranges vary between 0.2 and 0.48 km² (0.08 and 0.19 mi²), with no or little overlap (Papaioannou 1973; Chivers 1974; Raemaekers 1979; MacKinnon & MacKinnon 1980; Raemaekers & Chivers 1980; Palombit 1996b; O’Brien et al. 2003). Average day ranges of siamang groups range between 640-1289 m (Chivers 1974; Raemaekers 1979; MacKinnon & MacKinnon 1980; Lappan 2005; Bartlett 2007). During wet months, daily travel is shorter than in dry months (Raemaekers 1980). Siamangs spend most of their time high in the forest canopy, over 24 meters (78.7 ft) above the ground, but will also descend to around 7.5 meters (24.6 ft) above the ground and rarely lower (MacKinnon & MacKinnon 1980). Arboreal group movements are usually in single-file through the same pathway (Chivers 1974).

Siamangs live in sympatry with a number of other primates including the slow loris (Nycticebus coucang), long-tailed macaque (Macaca fascicularis), pigtail macaque (Macaca nemestrina), Thomas’s langur (Presbytis thomasi), lar gibbon (Hylobates lar), agile gibbon (Hylobates agilis), banded langur (Presbytis melalophos), ebony langur (Trachypithecus auratus), Horsfield’s tarsier (Tarsius bancanus), and Sumatran orangutan (Pongo abelii) (Palombit 1992; Lappan 2005). In addition, in northern Sumatra, siamangs are sympatric with orangutans and lar gibbons, the only place in the world where three species of non-human apes coexist (Palombit 1996b). The siamang and other gibbons with which it is sympatric might compete for food as in some cases there is diet overlap (Raemaekers 1984). This is the case with the sympatric lar gibbon where infrequent confrontations between siamangs and the species over food resources have been observed (Raemaekers 1978). In addition, in at least one study, a male siamang associated with a male lar gibbon and the pair traveled, fed, and even chorused together (MacKinnon & MacKinnon 1977).

In general, predation on gibbons is not well documented, and in no field study of either Hylobates sp. or Symphalangus syndactylus has direct predation been observed (see Uhde & Sommer 2002). However, a full-sized siamang was found in the digestive tract of a python (Schneider 1906 cited in Uhde & Sommer 2002).

Content last modified: May 20, 2008

Written by Kurt Gron. Reviewed by Alan Mootnick.

Cite this page as:
Gron KJ. 2008 May 20. Primate Factsheets: Siamang (Symphalangus syndactylus) Taxonomy, Morphology, & Ecology . <>. Accessed 2020 July 10.


In general, most siamangs live in monogamous pairs accompanied by up to 6 immature individuals, with usual group membership between 2 and 6 individuals (Kawabe 1970; MacKinnon & MacKinnon 1980; Raemaekers & Chivers 1980; Norikoshi 1986; Palombit 1992; 1996; Lappan 2005). However, groups with multiple adult males are known, and such groups can be sexually polyandrous and can last several years (Lappan 2005). While monogamy was considered the rule and siamangs were considered strictly monogamous, it now appears that the pair-bonds are much more dynamic than originally thought and extra-group copulations are known in the species (Palombit 1992; 1994a). Further, changes in the mating pair can be precipitated by several means, including replacement of one of the pair by an extra-group siamang, mate desertion, co-dispersal, and father-son mating replacements (Palombit 1994b).

Two Simangs sitting on a rock face
Symphalangus syndactylus

Both male and female siamangs cooperatively maintain their territory through several means; ranging near the territorial edges (patrolling), calling at (singing) and confronting (chasing and interacting with) intruders, in addition to loud calling in the morning (Chivers 1974; Orgeldinger 1991; Palombit 1996b). The territory is actively defended from other siamang groups and from solitary individuals (Palombit 1996b). In captivity, males participate more in non-vocal territorial defense than do females (Orgeldinger 1997). Singing or duetting occurs infrequently, only about once every 4-5 days and is usually heard in the morning although not before dawn (Kawabe 1970; Gittins 1980; Palombit 1996b). Such calling can be heard more than 2 km (1.2 mi) away and can last up to twenty minutes but the discrete function of this calling is unknown (Kawabe 1970; Lamprecht 1970; Palombit 1996b). Inter-group interactions usually occur along the periphery of a specific siamang group’s territory, and can last up to several hours. Usually these interactions do not result in injuries, but consist of vocalizations, displays and chasing (Palombit 1996b).

For the most part, members of a siamang group usually spend the day within 10 m (32.8 ft) of other group members, and rarely more than 30 m (98.4 ft) apart (Chivers 1974). Agonistic gestures occur infrequently, but consist of open-mouth threats, grimace and lip-smacking displays (Palombit 1996a). Grooming is the most common form of physical social interaction, but most bouts last less than 5 minutes. In addition, grooming is usually between mature individuals, and mostly happens later in the day (Chivers 1974). When resting or relaxing, siamang pairs will huddle or maintain physical contact (Palombit 1996a).

In the wild, gibbons (including siamangs) exhibit a lack of dominance over one another (Gittins & Raemaekers 1980). In captivity, there is no dominant sex, with co-dominance occurring sometimes, while in other cases the male was dominant to the female and the female dominant to the male (Orgeldinger 1991). Within multi-male siamang groups, there can be low levels of aggression and affiliative behaviors between males can occur (Lappan 2007).

Both males and females emigrate, however there is evidence that females typically disperse long distances and males, while variable in their dispersal distances, emigrate only short distances from their natal groups (Chivers & Raemaekers 1980; Palombit 1996b; Lappan 2007). Emigration from the natal group usually occurs at sexual maturity (around 8-10 years old), after which the young adults leave, resulting from increased peripheralization and agonism from the resident adults (Chivers 1974; Palombit 1996b).


The siamang reproductive system is characterized by monogamy in most cases, however in uncommon multi-male groups polyandrous mating occurs (Palombit 1996b; Lappan 2005). Also, mating with individuals outside of the pair-bond occurs, usually with adult or sub-adult members of a neighboring group (Palombit 1994a; 1996b). Siamang females exhibit externally visible changes in the sex skin changing from black to red and white although it is unclear if the color changes are associated with ovulation or menstruation (Chivers 1974). Copulation in captivity usually takes place in the context of bonding or resting behaviors (Orgeldinger 1996).

The usual copulatory posture consists of a male approaching behind a female and mounting, copulating in a dorso-ventral position (Chivers 1978; Orgeldinger 1991). However in the wild, other copulatory positions have been observed, including suspended and face-to-face copulation (Aldrich-Blake pers. comm. cited in Chivers 1978; Chivers & Raemaekers 1980). Ventro-ventral mating postures have been seen in captivity as well (Orgeldinger 1991). Copulations occur at any time of the day (Chivers 1974).

There may be seasonality of mating in wild siamangs. Conception occurs mostly between May and July during flowering-fruiting peaks, with births between December and February, however copulations have been observed outside of this peak, and infants have been seen in August and September (Koyama 1971; Chivers 1978; Chivers & Raemaekers 1980). Potential seasonality could be due to ecological conditions at birth which are conducive for lactation as well as food availability during pregnancy (Chivers 1978). During a breeding period, sexual activity occurs about once per day on alternating days (Chivers 1974).

The age of sexual maturity in siamangs is estimated at between 8 and 9 years of age and interbirth intervals are commonly greater than three years in the wild (Geissmann 1991; Palombit 1992).

Captive autosexual behavior has been observed (Mootnick & Baker 1994).


At birth in captivity, siamang infants weigh on average 536.9 g (18.9 oz) but can range between 390 and 685 g (13.8 and 24.2 oz) (Geissmann & Orgeldinger 1995). Neonates are grey-pink with only meager hairs, but by one week of age the body is covered with hair except for the head. By the second week, the head has fur as well (Soo-Hoo 1966; Chivers & Chivers 1975; Palombit 1992). The birth of twins does occur but is rare, and in the event of twinning, the infants tend to develop somewhat faster than single births (Dal Pra & Geissmann 1994). In captivity, the majority of births take place at night (Orgeldinger 1991).

Siamang mother and infant
Symphalangus syndactylus

In the wild, immediately after birth, all of the infant’s time is spent either clinging to the mother in a ventral position or being carried by the mother (Lappan 2005; Liebal 2007). After three months of age however, the amount of maternal carrying time decreases steadily (Lappan 2005). In both the wild and in captivity, as the infant develops, contact between the mother and the infant slowly decreases while contact between the father and the infant increases (Chivers 1974; Alberts 1987). In captivity at around one year of age, the infant seeks paternal contact more than maternal contact (Alberts 1987). In the wild this is seen as well at around one year of age, where the mother becomes intolerant of the infant, and the father assumes care (Chivers 1974; Gittins & Raemaekers 1980). In captivity and in the wild, the father does most of the carrying at about one year of age or slightly later, and other group members, especially siblings, sometimes also carry the infant (however, when observed in captivity, this may have been the result of the infants in question being twins) (Chivers 1974; Dielentheis et al. 1991; Dal Pra & Geissmann 1994; Lappan 2005). In some cases, captive parental care of the infant is almost evenly divided between both parents, and the amount of wild male care of infants varies substantially, even within the same study population, and especially when multi-male groups are compared to single-male groups (Ferenc & Wielich 2000; Lappan 2005). In the wild, it is under paternal care that the infant learns to move independently, feed, and socially interact. Under the care of the male in the second year of life, carrying decreases significantly as independent travel increases (Chivers 1974). By 15 months of age, a large proportion of independent travel is seen (Lappan 2005). At three years of age, only occasional parental help in travel is offered (Chivers 1974).

In captivity, around 9 weeks of age, the infant gains some independence from the mother, but still maintains contact with her, with a complete lack of contact first seen at around 16 weeks. Solid foods are first consumed around 12 weeks old. One-armed suspension starts at 24 weeks of age, and the first brachiation is seen at 35 weeks. Bipedal locomotion starts at 43 weeks. Sibling play starts at 29 weeks, and receiving grooming from siblings starts at 13 weeks. Grooming of others starts at 45 weeks, and the infants will first call at 32 weeks (means compiled from several captive studies by Dal Pra & Geissmann 1994:335). In the wild however, social play develops only during the 2nd year of life and usually occurs during group rest (Chivers 1974). In addition, most infants in the wild do not consume solids until 6 months of age (Lappan 2005).

In the wild, weaning starts as early as 3 months, but is normally not complete until about a year of age, and sometimes longer (Chivers & Raemaekers 1980; Lappan 2005).

Infanticide by males is reported in captivity (Orgeldinger 1991). In addition, in captivity when a nearly one year old infant died, both parents significantly increased their social behavior, including copulations (Orgeldinger 1996). Gestation can be between 189 and 239 days but is most likely around 210 days (Geissmann 1991).


In captivity, a total of 20 communicatory gestures are observed; 8 visual and 12 relating to touch. Touch gestures are more commonly seen than visual gestures, and in general, gestures are associated with play (37.4%), grooming (23.2%), agonistic interactions (11.7%), and other interactions (<10%) (Liebal et al. 2004; Liebal 2007). There is inter-individual variation in the production of gestures and in one study, no individual performed all of them, and most performed only about half of the repertoire (Liebal 2007). In addition to communicatory gestures, the species exhibits 7 communicatory actions and 4 facial expressions (Liebal et al. 2004). Communication actions are usually seen during play (94.6% of instances) and facial expressions are usually seen during grooming (35.3% of instances) (Liebal et al. 2004).

Siamang howling in a tree
Symphalangus syndactylus

Siamang calls can be heard over a distance of over 1.5-2 km (0.9-1.2 mi) and are usually performed at the highest (emergent) levels of the canopy (Kawabe 1970; Chivers 1974; Gittins & Raemaekers 1980). The characteristic throat sac functions in calling to influence the character of, to resonate and to amplify vocalizations (Tembrock 1974; Chivers unpub. data cited in Barkell 1988). Singing occurs usually in the morning, about once every 4-5 days in the wild (Palombit 1996b). Sometimes termed a “duet,” these calling bouts last 10-20 minutes and are mostly performed by the mating pair, and sometimes other members of the group (Palombit 1996b; Geissmann 2000). Group calls can be divided into three categories of vocalization; “booms,” “barks,” and “screams” (Chivers 1974). In addition, contained within the “duet,” is the so-called female-only “great call” which is the culmination of the “duet” and comprises all types of vocalizations, including “barks” and “booms” (Palombit 1996b; Geissmann 2000). Calling bouts are stereotyped and are also sometimes accompanied by locomotion, however the function of such bouts is incompletely known (Palombit 1996b). Possible purposes for calling could be to maintain or strengthen the pair-bond and for territorial defense (Lamprecht 1970; Geissmann 1999). In general, the more elaborate communicatory bouts characterize interactions between neighboring groups (Chivers 1996). Similar in structure to “duets” are alarm call bouts, which serve a different function and provoke responses from neighboring siamang groups as well as being heard in potentially threatening situations (Chivers 1974; Geissmann 2000). At a sign of danger, group members will sometimes emit soft grunts, and if the threat persists, this will expand into barking by other members of the group at the same time (Chivers 1974).

In the wild, facial expressions, gestures, and calls are few in number in normal intra-group interactions (Chivers 1974). Infants will squeal or bleat when distressed, especially when the infant is isolated or trying to follow other group members (Chivers 1974). Other intra-group vocalizations include the “squeal,” which is used to show submission during aggressive interactions, feeding “glunks” which may be communicatory and “gurgles” which are heard from immature individuals while playing (Chivers 1974; 1976).

In captivity, some siamangs will place the palm of their hand in front of their mouth at various times during their vocalizations, possibly to allow an individual siamang to hear their own voice better by reflecting the vocalizations toward their ear, to modify sound production, or to maintain synchronous rhythms (Badraun et al 1998).

The siamang possesses a gland on its sternum which might function in olfactory communication (Geissmann 1987; 1993).

Content last modified: May 20, 2008

Written by Kurt Gron. Reviewed by Alan Mootnick.

Cite this page as:
Gron KJ. 2008 May 20. Primate Factsheets: Siamang (Symphalangus syndactylus) Behavior . <>. Accessed 2020 July 10.


For individual primate species conservation status, please search the IUCN Red List.
Also search the current scientific literature for primate conservation status (overall as well as for individual species), and visit CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora).

Conservation information last updated in 2008 follows, for comparison:

Symphalangus syndactylus>

The total siamang population for Indonesia (i.e. Sumatra) is estimated at 360,000 individuals in 1987, however in 2008, at the Indonesian Gibbon Workshop, it was determined that the Sumatran siamang populations numbered less than 200,000 individuals (MacKinnon 1987; A. Mootnick pers comm). Among the gibbons, siamangs appear to be among the more able to cope with habitat degradation and change (Geissmann et al. 2006; 2007).


Threat: Human-Induced Habitat Loss and Degradation

As in most primate species, habitat loss presents one of the most profound and ongoing threats to the survival of the siamang. It is estimated that siamags have lost 70-80% of their habitat in the last 50 years and the destruction continues (Geissmann 2007). Forest clearance is usually for agricultural land, logging, mining, roads, and electrical power lines (MacKinnon 1986; A. Mootnick pers. comm.). There are two main ways in which forests are logged in Southeast Asia; clear cutting and selective logging (MacKinnon 1987). Even selectively logged forests are very poor habitat for siamangs and other gibbons as brachiation requires a continuous canopy (MacKinnon 1984). In recent years, illegal deforestation on Sumatra has increased and in one survey of the southern portion of the island, almost every forest visited had undergone or was undergoing, some degree of habitat destruction. While able to cope with some habitat degradation, in more highly disturbed habitats, siamangs are absent (Geissmann et al. 2006; 2007). Further, road building has the potential to degrade siamang habitat by increasing farming, settlement, and logging. It does this by creating opportunities for the transportation and sale of forest products, as occurred within the borders of the Gunung Leuser National Park on Sumatra (Palombit 1992). Finally, traditional use of forest products by local residents is ongoing, but is small in scale and only for personal use (Palombit 1992).

Threat: Harvesting (hunting/gathering)

Siamangs, especially young individuals, are sold in wildlife markets as pets (often openly) even though they are a protected species. Often, these young are taken by killing a parent who is carrying the infant, a technique that sometimes causes the death of the young siamang as well (Crockett & Wilson 1980; Geissmann et al. 2006). In addition to being sold and kept locally as pets, siamangs are also sometimes exported illegally or sold elsewhere in Indonesia as evidenced by siamangs found for sale in markets on Java (Crockett & Wilson 1980; Malone et al. 2002). Collection of siamangs as pets can result from logging, with the animals being collected after their habitat is destroyed (O’Brien et al. 2004).

At least in southern Sumatra, siamangs are not hunted for food, and in some areas, religion precludes the eating of primates (Palombit 1992; O’Brien et al. 2004).

Threat: Natural Disasters

Forest fires precipitated by El Niño/Southern Oscillation (ENSO) events also represent a threat to siamang populations. Such events are increasing in frequency, and correspondingly, forest fires have the potential to do so as well. Following wildfires, siamang groups are smaller and have lower offspring survival rates, as well as fewer numbers of preferred food species available to them (O’Brien et al. 2003).





Content last modified: May 20, 2008

Written by Kurt Gron. Reviewed by Alan Mootnick.

Cite this page as:
Gron KJ. 2008 May 20. Primate Factsheets: Siamang (Symphalangus syndactylus) Conservation . <>. Accessed 2020 July 10.

The following references were used in the writing of this factsheet. To find current references for siamangs, search PrimateLit.


Alberts S. 1987. Parental care in captive siamangs (Hylobates syndactylus). Zoo Biol 6(4):401-6.

Andrews P, Groves CP. 1976. Gibbons and brachiation. Gibb Siam 4:167-218.

Ankel-Simons F. 2000. Primate anatomy: an introduction, second edition. San Diego: Academic Pr. 506 p.

Badraun JC, Mootnick AR, Deaner RO, Agoramoorthy G, McNeese KM. 1998. Hand modulation of vocalization in siamangs Hylobates syndactylus. Intl Zoo Ybk 36:84-9.

Barkell C. 1988. The vocalizations of captive siamangs. Aust Primatol 3(1):2-3.

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.

Bertram JEA. 2004. New perspectives on brachiation mechanics. Ybk Phys Anth 47:100-17.

Caldecott JO. 1980. Habitat quality and populations of two sympatric gibbons (Hylobatidae) on a mountain in Malaya. Folia Primatol 33(4):291-309.

Chivers DJ. 1976. Communication within and between family groups of siamang (Symphalangus syndactylus). Behaviour 57:116-35.

Chivers DJ, Chivers ST. 1975. Events preceding and following the birth of a wild siamang. Primates 16(2):227-30.

Chivers DJ. 1977. The feeding behaviour of siamang (Symphalangus syndactylus). In: Clutton-Brock TH, editor. Primate ecology: studies of feeding and ranging behaviour in lemurs, monkeys and apes. London: Academic Pr. p 355-82.

Chivers DJ. 1985. Gibbons. In: Macdonald D, editor. All the world’s animals: primates. New York: Torstar Books Inc. p 118-23.

Chivers DJ. 1980. Introduction. In: Chivers DJ, editor. Malayan forest primates: ten years’ study in tropical rain forest. New York: Plenum Pr. p 1-27.

Chivers DJ, Raemaekers JJ, Aldrich-Blake FPG. 1975. Long-term observations of siamang behaviour. Folia Primatol 23:1-49.

Chivers DJ. 1978. Sexual behaviour of wild siamang. In: Chivers DJ, Herbert J, editors. Recent advances in primatology, volume one: behaviour. London: Academic Pr. p 609-10.

Chivers DJ. 1972a. The siamang and the gibbon in the Malay peninsula. Gibb Siam 1:103-35.

Chivers DJ. 1972b. The siamang in Malaya. PhD dissertation, Cambridge U.

Chivers DJ. 1974. The siamang in Malaya: a field study of a primate in tropical rain forest. Contrib Primatol 4:1-335.

Crockett C, Wilson WL. 1980. Survey of Sumatran primates: diversity and abundance in a shrinking paradise. Tigerpaper 7(2):1-5.

Dal Pra G, Geissmann T. 1994. Behavioural development of twin siamangs (Hylobates syndactylus). Primates 35(3):325-42.

Dielentheis TF, Zaiss E, Geissmann T. 1991. Infant care in a family of siamangs (Hylobates syndactylus) with twin offspring at Berlin zoo. Zoo Biol 10(4):309-17.

Ferenc H, Wielich A. 2000. Parental behaviour in a siamang family group at Poznan zoo. Intl Zoo News 47(7):427-31.

Geissmann T. 2003. Circumfacial markings in siamang and evolution of the face ring in the Hylobatidae. Intl J Primatol 24(1):143-56.

Geissmann T. 2000. Duet songs of the siamang, Hylobates syndactylus: I. structure and organization. Prim Rep 56:33-60.

Geissmann T. 1999. Duet songs of the siamang, Hylobates syndactylus: II. Testing the pair-bonding hypothesis during a partner exchange. Behaviour 136(8):1005-39.

Geissmann T. 1993. Evolution of communication in gibbons (Hylobatidae). PhD dissertation, Universität Zürich. 374 p.

Geissmann T, Nijman V, Dallmann R. 2006. The fate of diurnal primates in southern Sumatra. Gibb J 2:18-24.

Geissmann T, Orgeldinger M. 1995. Neonatal weight in gibbons (Hylobates spp.). Am J Primatol 37(3):179-89.

Geissmann T. 1991. Reassessment of age of sexual maturity in gibbons (Hylobates spp.). Am J Primatol 23(1):11-22.

Geissmann T. 2007. Status reassessment of the gibbons: results of the Asian primate red list workshop 2006. Gibb J 3:5-15.

Geissmann T. 1987. A sternal gland in the siamang gibbon (Hylobates syndactylus). Intl J Primatol 8(1):1-15.

Gittins SP, Raemaekers JJ. 1980. Siamang, lar, and agile gibbons. In: Chivers DJ, editor. Malayan forest primates: ten years’ study in tropical rain forest. New York: Plenum Pr. p 63-105.

Gittins SP. 1980. Territorial advertisement and defense in gibbons. In: Preuschoft H, Chivers DJ, Brockelman WY, Creel N, editors. The lesser apes: evolutionary and behavioural biology. Edinburgh: Edinburgh U Pr. p 420-4.

Groves C. 2005. Order primates. In: Wilson DE, Reeder DM, editors. Mammal species of the world: a taxonomic and geographic reference, third edition, volume 1. Baltimore (MD): Johns Hopkins U Pr. p 111-84.

Groves CP. 1972. Systematics and phylogeny of gibbons. Gibb Siam 1:1-89.

Jenkins PD. 1990. Catalogue of primates in the British museum (natural history) and elsewhere in the British isles, part V: the apes, superfamily hominoidea. London: Natural History Museum Pub. 137p.

Kawabe M. 1970. A preliminary study of the wild siamang gibbon (Hylobates syndactylus) at Fraser’s Hill, Malaysia. Primates 11:285-91.

Koyama N. 1971. Observations on mating behavior of wild siamang gibbons at Fraser’s Hill, Malaysia. Primates 12(2):183-9.

Lamprecht VJ. 1970. Duettgesang beim siamang, Symphalangus syndactylus (Hominoidea, Hylobatinae). Z Tier 27:186-204.

Lappan S. 2005. Biparental care and male reproductive strategies in siamangs (Symphalangus syndactylus) in southern Sumatra. PhD dissertation, New York University. 312 p.

Lappan S. 2007. Patterns of dispersal in Sumatran siamangs (Symphalangus syndactylus): preliminary mtDNA evidence suggests more frequent male than female dispersal to adjacent groups. Am J Primatol 69(6):692-8.

Liebal K. 2007. Gestures in siamangs (Symphalangus syndactylus). In: Call J, Tomasello M, editors. The gestural communication of apes and monkeys. Mahwah (NJ): Lawrence Erlbaum Assc. p 131-58.

Liebal K, Pika S, Tomasello M. 2004. Social communication in siamangs (Symphalangus syndactylus): use of gestures and facial expressions. Primates 45(1):41-57.

MacKinnon K. 1986. The conservation status of nonhuman primates in Indonesia. In: Benirschke K, editor. Primates: the road to self-sustaining populations. New York: Springer-Verlag. p 99-126.

MacKinnon K. 1987. Conservation status of primates in Malesia, with special reference to Indonesia. Prim Conserv 8: 175-83.

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.

MacKinnon JR. 1984. The distribution and status of gibbons in Indonesia. In: Preuschoft H, Chivers DJ, Brockelman WY, Creel N, editors. The lesser apes: evolutionary and behavioural biology. Edinburgh (UK): Edinburgh U Pr. p 16-8.

MacKinnon J, MacKinnon K. 1977. The formation of a new gibbon group. Primates 18(3):701-8.

Malone N, Purnama AR, Wedana M, Fuentes A. 2002. Assessment of the sale of primates at Indonesian bird markets. Asia Prim 8(1-2):7-11.

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.

Medway L. 1972. The Gundong Benom expedition 1967, VI: the distribution and altitudinal zonation of birds and mammals on Gunong Benom. Bull Brit Mus Nat Hist Zool 23:105-54.

Mootnick AR. 2006. Gibbon (Hylobatidae) species identification recommended for rescue or breeding centers. Prim Conserv 21:103-38.

Mootnick AR, Baker E. 1994. Masturbation in captive Hylobates (Gibbons). Zoo Biol 13(4):345-53.

Norikoshi K. 1986. Socio-ecological study of siamangs in Maninjau, west Sumatra. Kyoto U Over Res Rep Stud Asia Non-Hum Prim 5:29-43.

O’Brien TG, Kinnaird MF, Nurcahyo A, Iqbal M, Rusmanto M. 2004. Abundance and distribution of sympatric gibbons in a threatened Sumatran rain forest. Intl J Primatol 25(2):267-84.

O’Brien TG, Kinnaird MF, Nurcahyo A, Prasetyaningrum M, Iqbal M. 2003. Fire, demography and the persistence of siamang (Symphalangus syndactylus: Hylobatidae) in a Sumatran rainforest. Anim Conserv 6(2):115-21.

Orgeldinger M. 1996. Behavioural changes following the death of a siamang infant. Intl Zoo News 43(6):426-33.

Orgeldinger M. 1994. Monitoring body weight in captive primates, with special reference to siamangs. Intl Zoo News 41(1):17-26.

Orgeldinger M. 1997. Protective and territorial behavior in captive siamangs (Hylobates syndactylus). Zoo Biol 16(4):309-25.

Orgeldinger M. 1991. Siamangs (Hylobates syndactylus) in captivity: an overview. Intl Zoo News 38(6):5-13.

Palombit RA. 1994b. Dynamic pair bonds in Hylobatids: implications regarding monogamous social systems. Behaviour 128(1-2): 65-101.

Palombit RA. 1994a. Extra-pair copulations in a monogamous ape. Anim Behav 47(3):721-3.

Palombit RA. 1997. Inter- and intraspecific variation in the diets of sympatric siamang (Hylobates syndactylus) and lar gibbons (Hylobates lar). Folia Primatol 68(6):321-37.

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.

Palombit RA. 1996a. Pair bonds in monogamous apes: a comparison of the siamang Hylobates syndactylus and the white-handed gibbon Hylobates lar. Behaviour 133(5-6):321-56.

Palombit RA. 1996b. The siamang and white-handed gibbon of Gunung Leuser National Park. In: van Schaik CP, Supriatna J, editors. Leuser: a Sumatran sanctuary. Jakarta: Yayasan Bina Sains Hayati Indonesia (YABSHI). p 269-79.

Papaioannou J. 1973. Observations on locomotor and general behaviour of the siamang. Malay Nat J 26:46-52.

Raemaekers J. 1980. Causes of variation between months in the distance traveled daily by gibbons. Folia Primatol 34:46-60.

Raemaekers J. 1979. Ecology of sympatric gibbons. Folia Primatol 31:227-45.

Raemaekers J. 1984. Large versus small gibbons: relative roles of bioenergetics and competition in their ecological segregation in sympatry. In: Preuschoft H, Chivers DJ, Brockelman W, Creel N, editors. The lesser apes: evolutionary and behavioural biology. Edinburgh: Edinburgh U Pr. p 209-18.

Raemaekers JJ. 1978. The sharing of food sources between two gibbon species in the wild. Malay Nat J 31(3):181-8.

Raemaekers JJ, Chivers DJ. 1980. Socio-ecology of Malayan forest primates. In: Chivers DJ, editor. Malayan forest primates: ten years’ study in tropical rain forest. New York: Plenum Pr. p 279-316.

Schmidt VCR, Weigl R. 1999. Hohe lebensdauer beim siamang, Symphalangus syndactylus. Zool Garten 69(3):192-3.

Schneider G. 1906. Ergebnisse zoologischer forschungsreisen in Sumatra. Zoologische Jahrbücher Abteilung Systematik, Geographie und Biologie der Tiere 23:1-172.

Schultz AH. 1933. Observations on the growth, classification and evolutionary specialization of gibbons and siamangs. Hum Biol 5:212-55; 385-428.

Soo-Hoo C. 1966. A brief note on the birth of a siamang Hylobates syndactylus at San Francisco zoo. Intl Zoo Ybk 6:147.

Tembrock G. 1974. Sound production of Hylobates and Symphalangus. Gibb Siam 3:176-205.

Treesucon U. 1997. Siamang (Hylobates syndactylus): a new mammal recorded for Thailand. Nat Hist Bull Siam Soc 45:123-4.

Uhde NL, Sommer V. 2002. Antipredatory behavior in gibbons (Hylobates lar, Khao Yai/Thailand). In: Miller LE, editor. Eat or be eaten: predator sensitive foraging among primates. Cambridge: Cambridge U Pr. p 268-91.

Weigl R. 2005. Longevity of mammals in captivity; from the living collections of the world. Stuttgart (DE): E. Schweizerbartsche. 214 p.

Wilson CC, Wilson WL. 1976. Behavioral and morphological variation among primate populations in Sumatra. Ybk Phys Anth 20:207-233.

Content last modified: May 20, 2008


Symphalangus syndactylus
Photo: Alan H. Shoemaker
Two Simangs sitting on a rock face Symphalangus syndactylus
Photo: Alan H. Shoemaker
Symphalangus syndactylus
Photo: Alan H. Shoemaker
Symphalangus syndactylus
Photo: Alan H. Shoemaker
Symphalangus syndactylus
Photo: Alan H. Shoemaker
Siamang Symphalangus syndactylus
Photo: Alan Mootnick
Symphalangus syndactylus
Photo: Anne Savage
Symphalangus syndactylus
Photo: Anne Zeller
Symphalangus syndactylus
Photo: Anne Zeller
Symphalangus syndactylus
Photo: E. C. Oaks
Siamang howling in a tree Symphalangus syndactylus
Photo: Roy Fontaine
Siamang mother and infant Symphalangus syndactylus
Photo: Roy Fontaine

Primate Info Net (PIN) is maintained by the Wisconsin National Primate Research Center (WNPRC) at the University of Wisconsin-Madison, with countless grants and contributions from others over time. PIN is an ever-growing community effort: if you’d like to contribute, or have questions, please don’t hesitate to contact us.