The majority of wild Sumatran orangutans survive in the province of Aceh (more formally known as Nanggroe Aceh Darussalam, or NAD), at the northernmost tip of the island. There are populations within North Sumatra province, but the largest of these also straddles the border with Aceh. Only two potentially viable populations lie entirely within North Sumatra province: West Batang Toru and East Sarulla, both near, but south-west of lake Toba (for precise locations see Singleton et al. 2004).
Within Aceh, almost all remaining forest patches of any size still harbour orangutans at the lower altitudes, but there are few, if any reproducing populations in the large tracts of forest above 1,000 m asl.
Sumatran orangutans inhabit the island of Sumatra, in Indonesia. These orangutans have been restricted to the northern tip of Sumatra in fragmented forest. Logging has severely limited the range of this species.
Biogeographic Regions: oriental (Native )
Other Geographic Terms: island endemic
- WWF. 2007. "Sumatran orangutan" (On-line). WWF. Accessed October 17, 2007 at http://www.panda.org/about_wwf/what_we_do/species/about_species/species_factsheets/great_apes/orangutans/sumatran_orangutan/index.cfm.
- Rijksen, H. 1978. A field study on Sumatran oran utans (Pongo abelii): ecology, behavious and conservation.. WAU Dissertation Abstracts, Dissertation no. 710: 1-2. Accessed September 26, 2007 at http://library.wur.nl/wda/abstracts/ab710.html.
- Singleton, I., C. van Schaik. 2002. The Social Organisation of a Population of Sumatran Orang-Utans. Karger Journals, 73: 1-20. Accessed September 26, 2007 at http://content.karger.com/ProdukteDB/produkte.asp?typ=pdf&doi=60415.
Sumatran orangutans are the largest non-human primates in Asia and the largest arboreal primates. They have long, fine red hair on their bodies and faces. Males have large cheek pads that are covered in a fine white hairs.The arm span, from finger tip to finger tip, is 2.25 m. The legs are small and weak compared to their muscular arms. There is sexual dimorphism between males and females. Female weights range from 30 to 50 kg and they can reach 1.3 m tall. Male weights range from 50 to 90 kg and reach a height of 1.8 m. Some old males may get too large to move around in trees easily and may have to resort to walking on the ground.
Sumatran orangutans may be distinguished from Bornean orangutans (Pongo pygmaeus) by their longer fur, more slender build, white hairs on the face and groin, and long beards on both males and females, but molecular characters are considered most definitive.
Range mass: 30 to 90 kg.
Range length: 1.3 to 1.8 m.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger; sexes shaped differently; ornamentation
- Maple, T. 1980. Orang-utan Behavior. Van Nostrand Reinhold Company. New York, NY: Van Nostrand Reinhold Company.
- Cocks, L. 2003. Orangutans: And Their Battle for Survival. Claremont, West Australia: University of Western Australia Press.
- WWF. 2007. "Sumatran Orangutan- Population & Distribution" (On-line). World Wildlife Foundation. Accessed September 26, 2007 at http://www.panda.org/about_wwf/what_we_do/species/about_species/species_factsheets/great_apes/orangutans/sumatran_orangutan/sumorangutan_population_distribution/index.cfm..
- Sumatran Orangutan Society, 2007. "Orangutan Facts" (On-line). Sumatran Orangutan Society. Accessed December 11, 2007 at http://www.orangutans-sos.org/faq.php.
Habitat and Ecology
Sumatran orangutans are primarily frugivores, but also eat leaves, insects (termites and ants) and on occasion, the meat of slow loris (Fox et al. 2004, Wich et al. 2006). Female home ranges are 800 to 1,500 ha. The true extent of male home range size is not fully known, although ranges in excess of 3,000 ha are inferred (Singleton and van Schaik 2001).
Females first give birth at about 15 years of age (Wich et al. 2004). Interbirth intervals are 8.2 to 9.3 years (compared with 6.1 to 7.7 years for P. pygmaeus; Wich et al. 2004, van Noordwijk and van Schaik 2005) and gestation lasts approximately 254 days (Kingsley 1981). Males exhibit bimaturism, whereby fully flanged adult males and the smaller unflanged males are both capable of reproducing, but employ differing mating strategies to do so (see Utami Atmoko et al. 2002). Longevity in the wild has been estimated at 58 years for males and 53 years for females (Wich et al. 2004).
Sumatran orangutans are found in primary tropical lowland forests, including mangrove, swamp forests, and riparian forests. They live almost completely in the trees, building nests in which they nap or sleep for the night. Preferred elevations are 200 to 400 m, the area in which their preferred fruiting trees occur, but Sumatran orangutans can be found up to 1,000 to 1,500 m.
Range elevation: 200 to 1,500 m.
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: rainforest
Other Habitat Features: riparian
- Rijksen, , Meijaard, Van Schaik. 2003. "DISTRIBUTION & HABITAT" (On-line). Accessed November 29, 2007 at http://spot.colorado.edu/~humphrey/fact%20sheets/orangutan/orangutan.htm.
Sumatran orangutan food choices vary seasonally. Most fruits are only available seasonally and within a limited range. Orangutans follow the fruiting season of local trees, feeding when they are ripe. Figs are one of the most important components of the Sumatran orangutan diet. During dry seasons, when fruit is less available, Sumatran orangutans will consume other vegetation. Fruit makes up about 60% of their diet, with the remainder being young leaves (~25%), flowers and bark (~10%), insects, mainly ants, termites, and crickets (~5%), and an occasional egg.
Animal Foods: eggs; insects
Plant Foods: leaves; wood, bark, or stems; seeds, grains, and nuts; fruit; flowers
Primary Diet: herbivore (Frugivore )
Sumatran orangutans play a critical role in the lowland rainforests of Sumatra and are considered a keystone species. As widely ranging fruit eaters, orangutans are important in dispersing seeds and maintaining diversity of rainforest woody plants. They also prune and aid in regenerating plant growth because they only choose to eat green leaves and stalks.
Ecosystem Impact: disperses seeds; keystone species
Species Used as Host:
- dipterocarp trees (Dipterocarpaceae)
The primary predators currently of Sumatran orangutans are humans (Homo sapiens). Hunting of orangutans has decimated their populations. Natural predators of Sumatran orangutans are clouded leopards (Neofelis nebulosa) and Sumatran tigers (Panthera tigris sumatrae). These predator species are also under threat of extinction due to hunting by humans.
- MacKinnon, J. 1974. In Search Of The Red Ape. Ballantine Books; A Division of Random House, Inc. New York, NY: Holt, Rinehart and Winston.
Life History and Behavior
Communication and Perception
Male Sumatran orangutans are capable of long, exceptionally loud calls (called "long calls") that carry through forests for up to 1 km. The "long call" is made up of a series of sounds followed by a bellow. These calls help males claim territory, call to females, and keep out intruding male orangutans. Males have a large throat sac that lets them make these loud calls. They may also pull small trees and limbs down to add a crashing sound along with the call. Sumatran orangutans vocalize with grunts, grumbles, and squeaks when they meet each other, and young orangutans squeak, bark and scream. Both adults and young make a variety of sounds with their lips and throats, including sucking, burping, and grinding their teeth.
Communication Channels: visual ; tactile ; acoustic
Perception Channels: visual ; acoustic
Female life spans range from 44 to 53 years in the wild. There have been no reports documenting the onset of menopause and females seem to be capable of giving birth up to 51 to 53 years old. Male life spans are slightly longer, 47 to 58 years. Males are still considered healthy at these late ages by the tightness of their cheek pads and absence of bald spots. A captive female Sumatran orangutan lived to 55 years at the Miami Zoo.
Status: wild: 44 to 58 years.
Status: captivity: 55 (high) years.
Status: wild: 58 (high) years.
The primary mating tactic involves "harassment" of female Sumatran orangutans by sub-adult males and adult males. Most harassment involves sub-adult males; females are less likely to mate with them, as compared to large adult males. Females are cornered by sub-adult males and may be raped by them; these sub-adult males may also take a female's young from her if they think it will make her more willing or available to mate.
Female orangutans have learned strategic ways to avoid or reduce harassment. The first method is a social tactic, where females form non-mating parties with adult male orangutans that reside in their area, reducing attacks from sub-adult males. Another is female-female bonding, where females alone form alliances to protect themselves against sub-adult males.
Harassment has also increased in the last decade due to habitat loss from illegal logging. More orangutans are forced into too small of an area, increasing agonistic interactions.
Mating System: polygynandrous (promiscuous)
Most mating occurs in the heaviest fruiting months. There is large variability in the amount of fruit from season to season. Highest fruiting periods happen during rainy seasons (December to May). Mast fruiting years, in which most of the trees of a single species fruit synchronously, occur every 2 to 10 years. Sumatran orangutan breeding is most intense in mast years. Any female who is not currently caring for offspring (pre-weaning) is available to mate. Females normally mate with the adult male whose large territory they live in, but chance encounters can happen in high fruiting seasons when many orangutans gather to feed. Females give birth to one young, twinning occurs rarely.
Adult female Sumatran orangutans become sexually active at the average age of 12.3 yrs and will produce their first offspring soon after. Male Sumatran orangutans are fully mature at an average age of 19 years.
Breeding interval: Interbirth intervals are 3 to 4 years.
Breeding season: Rainy seasons: December and May
Range number of offspring: 1 to 2.
Average number of offspring: 1.
Range gestation period: 227 to 275 days.
Average weaning age: 48 months.
Range time to independence: 8 to 9 years.
Average time to independence: 9.3 years.
Range age at sexual or reproductive maturity (female): 9 to 15.5 years.
Average age at sexual or reproductive maturity (female): 12.3 years.
Range age at sexual or reproductive maturity (male): 15 to 24 years.
Average age at sexual or reproductive maturity (male): 19 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous
After a female orangutan has given birth, her next 8 to 9 years are devoted to her offspring's survival. Infant and juvenile orangutans must learn everything (feeding, social behaviors, etc.) from their mothers. Mothers provide young orangutans with food until they have learned to distinguish different types of food. Males do not play a role in offspring care. Once fully developed, a male will leave his mother to find his own territory. A developed, independent young female will either disperse or take up residence near her mother's territory.
Parental Investment: altricial ; female parental care ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female); post-independence association with parents; extended period of juvenile learning
- Fox, E. 2002. Female tactics to reduce sexual harassment. Behavioral Ecology and Sociobiology, 52/2: 93-101.
- Wich, S., S. Utami-Atmoko, T. Mitra Setia, H. Rijksen, C. Schürmann. 2004. Life history of wild Sumatran orangutans ( Pongo abelii ). Journal of Human Evolution, 47/6: 385-398.
Molecular Biology and Genetics
Barcode data: Pongo abelii
There are 2 barcode sequences available from BOLD and GenBank. Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species. See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
-- end --
Download FASTA File
Statistics of barcoding coverage: Pongo abelii
Public Records: 3
Specimens with Barcodes: 3
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
- 2007Critically Endangered
- 2000Critically Endangered
Critical orangutan habitat is rapidly being lost through illegal and legal logging in Sumatra. Their habitat has decreased over 80% in the last 20 years. Hunting orangutans for meat and killing adult females to obtain infants for the illegal pet trade has also caused an estimated decline in the orangutan population of 30 to 50% in the last 10 years. Uncontrolled forest fires have also harmed orangutan habitat.
US Federal List: endangered
CITES: appendix i
State of Michigan List: no special status
IUCN Red List of Threatened Species: critically endangered
- Durrell Wildlife Conservation Trust. Sumatran Orangutan. 69. Durrell Wildlife Conservation Trust: Durrell Wildlife Conservation Trust. 2006. Accessed November 26, 2007 at http://www.durrell.org/Animals/Sumatran-Orangutan/.
Follow the link below for Table 1: Pongo abelii populations.
In addition to the above, original wild populations, a new population is being established in the Bukit Tigapuluh National Park (Jambi and Riau Provinces) via the re-introduction of confiscated illegal pets. This population currently numbers around 70 individuals and is reproducing.
A new threat is the Ladia Galaska road network in Aceh province, which if legitimized by the government will rapidly fragment most of the populations listed above. Another major concern is the re-issuing of logging permits for large tracts of forest in Aceh.
An assessment of forest loss in the 1990s concluded that forests supporting at least 1,000 orangutans were lost each year within the Leuser Ecosystem alone (van Schaik et al. 2001). These loss rates subsequently dropped dramatically during major civil conflict in the province, and the imposition of a moratorium on logging in Aceh. A peace deal negotiated in 2005 led to political stability and many new applications to open up logging concessions and palm oil estates in orangutan habitat.
In parts of North Sumatra orangutans are also still hunted on occasions for food.
A major stronghold is the Leuser Ecosystem conservation area: 2.6 million ha supporting circa 75% of remaining Sumatran orangutans. The Leuser Ecosystem was inaugurated by Presidential Decree in 1998 and its conservation is called for in the Act of Parliament No 11/2006 concerning Governance in Aceh. Management of the Ecosystem does not exclude non-forest uses, but stresses the importance of sustainable management with conservation of natural resources as the primary goal. Within the Leuser Ecosystem is the designated 900,000 ha Gunung Leuser National Park, but this mountainous area supports only 25% of the orangutans. The Gunung Leuser National Park is also a Man and Biosphere reserve and part of the Tropical Rainforest Heritage of Sumatra World Heritage Cluster Site. Outside of the Leuser Ecosystem there are no other notable large conservation areas harbouring this species.
In the wake of the December 2004 tsunami, efforts are also underway to establish a second ?Ulu Masen? ecosystem along similar lines to Leuser, incorporating the North East and North West Aceh populations. However, this process is in its early stages and there are already threats to open at least four large logging concessions in this area.
Relevance to Humans and Ecosystems
Economic Importance for Humans: Negative
There are no known negative affects of orangutans on humans. They are susceptible to many of the same diseases as humans, and thus can carry and transmit them as well, including tuberculosis, meliodosis, influenza, cholera, and intestinal parasites.
Negative Impacts: injures humans (carries human disease)
Economic Importance for Humans: Positive
Sumatran orangutans are important in seed dispersal. The protected status of orangutans make them an umbrella species. As umbrella species, if orangutans are protected, so is the rainforest they inhabit and all of its associated biodiversity.
There is still an active illegal trade in orangutans as pets.
Positive Impacts: pet trade ; research and education
- Thompson, G. 2007. "Orangutans sacrificed in palm oil boom" (On-line). ABC News. Accessed December 04, 2007 at http://www.abc.net.au/news/stories/2007/12/04/2108675.htm.
The Sumatran orangutan grows to about 1.4 m (4.6 ft) tall and 90 kg (200 lb) in males. Females are smaller, averaging 90 cm (3.0 ft) and 45 kg (99 lb). Compared to the Bornean species, Sumatran orangutans are thinner and have longer faces; their hair is longer with a paler red color.
Behaviour and ecology
Compared with the Bornean orangutan, the Sumatran orangutan tends to be more frugivorous and especially insectivorous. Preferred fruits include figs and jackfruits. It will also eat bird eggs and small vertebrates. Sumatran orangutans spend far less time feeding on the inner bark of trees.
Wild Sumatran orangutans in the Suaq Balimbing swamp have been observed using tools. An orangutan will break off a tree branch that is about a foot long, snap off the twigs and fray one end. It then will use the stick to dig in tree holes for termites. They will also use the stick to poke a bee's nest wall, move it around and catch the honey. In addition, orangutans use tools to eat fruit. When the fruit of the Neesia tree ripens, its hard, ridged husk softens until it falls open. Inside are seeds that the orangutans enjoy eating, but they are surrounded by fiberglass-like hairs that are painful if eaten. A Neesia-eating orangutan will select a five-inch stick, strip off its bark, and then carefully collect the hairs with it. Once the fruit is safe, the ape will eat the seeds using the stick or its fingers. Although similar swamps can be found in Borneo, wild Bornean orangutans have not been seen using these types of tools.
NHNZ filmed the Sumatran orangutan for its show Wild Asia: In the Realm of the Red Ape; it showed one of them using a simple tool, a twig, to pry food from difficult places. There is also a sequence of an animal using a large leaf as an umbrella in a tropical rainstorm.
The Sumatran orangutan is also more arboreal than its Bornean cousin; this could be because of the presence of large predators like the Sumatran Tiger. It moves through the trees by quadrumanous locomotion and semibrachiation.
The Sumatran orangutan is more social than its Bornean counterpart; groups gather to feed on the mass amounts of fruit on fig trees. However, adult males generally avoid contact with other adult males. Subadult males will try to mate with any female, though they probably mostly fail, since mature females are easily capable of fending them off. Mature females prefer to mate with mature males. Male Sumatran orangutans sometimes have a delay of many years in the development of secondary sexual characteristics, such as cheek flanges and muscle mass.
The average interbirth rates for the Sumatran orangutan is 9.3 years, the longest reported among the great apes, including the Bornean orangutan. Infant orangutans will stay close to their mothers for up to three years. Even after that, the young will still associate with their mothers. Both orangutan species are likely to live several decades; estimated longevity is more than 50 years. The average of the first reproduction of P. abelii is around 15.4 years old. There is no indication of menopause.
The Sumatran orangutan is endemic to Sumatra island and is particularly restricted to the north of the island. In the wild, Sumatran orangutans survive in the province of Nanggroe Aceh Darussalam (NAD), the northernmost tip of Sumatra. The primate was once more widespread, as they were found more to the south in the 19th century such as in Jambi and Padang. There are small populations in the North Sumatra province along the border with NAD, particularly in the Lake Toba forests. A survey in the Lake Toba region found only two inhabited areas, Bukit Lawang (defined as the animal sanctuary) and Gunung Leuser National Park. The species has been assessed as critically endangered on the IUCN Red List since 2000. It is considered one of "The World's 25 Most Endangered Primates."
A survey in 2004 estimated that around 7,300 Sumatran orangutans still live in the wild. Some of them are being protected in five areas in Gunung Leuser National Park; others live in unprotected areas: northwest and northeast Aceh block, West Batang Toru river, East Sarulla and Sidiangkat. A successful breeding program has been established in Bukit Tiga Puluh National Park in Jambi and Riau provinces.
Orangutans have 48 chromosomes. The Sumatran orangutan genome was sequenced in January 2011, based on a captive female named Susie. Following humans and chimpanzees, the Sumatran orangutan has become the third extant hominid species to have its genome sequenced.
The researchers also published less complete copies from 10 wild orangutans, five from Borneo and five from Sumatra. The genetic diversity was found to be lower in Bornean orangutans (Pongo pygmaeus) than in Sumatran ones (Pongo abelii), despite the fact that Borneo is home to six or seven times as many orangutans as Sumatra. The comparison has shown these two species diverged around 400,000 years ago, more recently than was previously thought. The orangutan genome also has fewer rearrangements than the chimpanzee/human lineage. The full sequence and annotation can be viewed on the Ensembl Genome Browser.
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- S. A. Wich; I. Singleton; S. S. Utami-Atmoko; M. L. Geurts; H. D. Rijksen; and C. P. van Schaik (2003). "The status of the Sumatran orang-utan Pongo abelii: an update". Flora & Fauna International 37 (1): 49. doi:10.1017/S0030605303000115.
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