| Tapanuli orangutan | |
|---|---|
 | |
| Adult male | |
 | |
| Adult female Both nearLake Toba | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Primates |
| Family: | Hominidae |
| Genus: | Pongo |
| Species: | P. tapanuliensis |
| Binomial name | |
| Pongo tapanuliensis Nurcahyo, Meijaard, Nowak, Fredriksson & Groves, 2017[note 1] | |
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| Approximate location in Sumatra | |
TheTapanuli orangutan (Pongo tapanuliensis) is aspecies oforangutan restricted toSouth Tapanuli in the island ofSumatra inIndonesia.[3] It is one of three known living species of orangutan, alongside theSumatran orangutan (P. abelii), found farther northwest on the island, and theBornean orangutan (P. pygmaeus). It was described as a distinct species in 2017.[4] As of 2018[update], there are roughly 800 individuals of this species and it is currently on thecritically endangered specieslist.[5]
An isolatedpopulation of orangutans in theBatang Toru area of South Tapanuli was reported in 1939.[6] The population was rediscovered by an expedition to the area in 1997,[7] but it was not recognized as a distinct species then.[8]Pongo tapanuliensis was identified as a distinct species, following a detailedphylogenetic study in 2017. The study analyzed thegenetic samples of 37 wild orangutans from populations across Sumatra and Borneo and conducted amorphological analysis of theskeletons of 34 adult males.[3] Theholotype of the species is the complete skeleton of an adult male from Batang Toru who died after being wounded by locals in November 2013.[3][9] The holotype is stored in theZoological Museum of Bogor.[3] Theskull andteeth of the Batang Toru male differ significantly from those of the other two orangutan species.[3][10] Comparisons of thegenomes of all 37 orangutans usingprincipal component analysis andpopulation genetic models also indicated that the Batang Toru population is a separate species.[3]
Thespecific name,tapanuliensis, as well as thecommon name, Tapanuli orangutan, refer to Tapanuli, the hilly region inNorth Sumatra where the species lives.[3][11]
Genetic comparisons show that Tapanuli orangutans diverged from Sumatran orangutans about 3.4 million years ago, and became more isolated after theLake Toba eruption that occurred about 75,000 years ago.[3][4][9] They had continued sporadic contact that stopped between 10,000 and 20,000 years ago. Tapanuli orangutans diverged from Bornean orangutans about 674,000 years ago.[10] Orangutans were able to travel from Sumatra to Borneo because the islands were connected byland bridges as parts ofSundaland duringrecent glacial periods when sea levels were much lower.[9] The present range of Tapanuli orangutans is thought to be close to the area whereancestral orangutans first entered what is nowIndonesia from mainland Asia.[3]
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Tapanuli orangutans resemble Sumatran orangutans more than Bornean orangutans in body build and fur color.[3] However, they have frizzier hair, smaller heads, and flatter and wide faces.[4] Dominant male Tapanuli orangutans have prominent moustaches and large flat cheek pads, known as flanges, covered in downy hair. The Tapanuli orangutan differs from the other two existing orangutan species in several specific features:
As with other two orangutan species, males are larger than females; males are 137 cm (54 in) in height and 70–90 kg (150–200 lb) in weight, females are 110 cm (43 in) in height and 40–50 kg (88–110 lb) in weight.[12]When comparing the Tapanuli orangutan with thePongo abelii, the Tapanuli orangutan has a deeper suborbital fossa, a triangular pyriform aperture, and a facial profile that is more angled.[3]
The loud, long-distance call or 'long call' of male Tapanuli orangutans has a higher maximumfrequency than that of Sumatran orangutans, and lasts much longer and has more pulses than that of Bornean orangutans.[3][9] Their diet is also unique, containing unusual items likecaterpillars andconifer cones.[10] Tapanuli orangutans are thought to be exclusivelyarboreal as scientists have not seen them descend to the ground in over 3,000 hours of observation. This is probably due to the presence ofSumatran tigers in the area.[13] Their other main predators areSunda clouded leopards,Sumatran dholes.[14] Tapanuli orangutans have slow reproductive rates causing a problem in increasing population.[15]
Tapanuli orangutans live intropical and subtropical moist broadleaf forests located south ofLake Toba in Sumatra. The entirety of the species is found in an area of about 1,000 km2 (390 sq mi) at elevations from 300 to 1,300 m (980 to 4,300 ft).[3] Tapanuli orangutans are separated from the island's other species of orangutan, the Sumatran orangutan, by just 100 km (62 mi).[11]
With fewer than 800 individuals restricted to an area of about 1,000 km2 (390 sq mi), the Tapanuli orangutan is the rarest great ape.[3] It is listed ascritically endangered by theInternational Union for Conservation of Nature (IUCN) because ofhunting,conflict with humans, theillegal wildlife trade, rampanthabitat destruction forsmall scale agriculture,mining and a proposedhydroelectric dam, theBatang Toru hydropower project, in the area with the highest density of orangutans, which could impact up to 10% of its already dwindling habitat and degrade importantwildlife corridors.[1][3][13] Conservationists predict an 83% decline in three generations (75 years) if the necessary conservation measures and practices are not implemented.[1]Inbreeding depression is likely due to the smallpopulation size and fragmented range. This is supported by the genomes of the two Tapanuli orangutan individuals, which show signs of inbreeding.[3] In August 2019 Swiss environmental group PanEco, which is a partner in theSumatran Orangutan Conservation Programme, dropped its previous opposition to the dam, several months after firing several researchers who opposed the new strategy.[16]
| Extant ape species |
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| Study of apes | ||
| Legal and social status | ||
| Related |
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