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Newly dis­cov­ered orang­utan species already Crit­i­cally Endangered

pub­lished 04 Novem­ber 2017 | mod­i­fied 04 Novem­ber 2017

Tapanuli orangutanA team of Indone­sian and inter­na­tional sci­en­tists have described a new species of orang­utan, that live in the Batang Toru Ecosys­tem in the North, Cen­tral and South­ern dis­tricts of Tapan­uli of Suma­tra, in a paper pub­lished on 2 Novem­ber in the sci­en­tific jour­nal Current Biol­ogy. The researchers demon­strate that the Tapan­uli orang­utan (Pongo tapan­ulien­sis), which live south of what had been the known range for Suma­tran orang­utans, is genet­i­cally and mor­pho­log­i­cally dis­tinct from both Bornean (Pongo pyg­maeus) and Suma­tran orang­utans (Pongo abelii), and is there­fore a sep­a­rate species. This new orang­utan is the first great ape species dis­cov­ery since the Bonobo from the Demo­c­ra­tic Repub­lic of Congo in 1929.

While there had been rumours long before, no one was sure that this new pop­u­la­tion of orang­utans existed until 1997. Ear­lier stud­ies sug­gested that the group dif­fered from other orang­utans behav­iourally and at the genetic level, but it wasn’t clear that those dif­fer­ences were enough to sup­port its des­ig­na­tion as a new species. The break­through came in 2013, when the research team got access to a skele­ton belong­ing to a Batang Toru orang­utan killed in a human-​animal con­flict. Care­ful stud­ies of the ani­mal revealed con­sis­tent dif­fer­ences in its skull and teeth.

A sophis­ti­cated analy­sis of 37 orang­utan genomes now shows that the Tapan­uli orang­utan — the Batang Toru pop­u­la­tion — diverged from the Bornean orang­utans to the north of Lake Toba about 3.4 mil­lion years ago. Bornean and Suma­tran orang­utans sep­a­rated only much later, less than 700,000 years ago. Behav­ioural and eco­log­i­cal evi­dence lends fur­ther sup­port for the notion that the orang­utans liv­ing in Batang Toru are a sep­a­rate species, the researchers said. Accord­ing to the find­ings, the Tapan­uli orang­utan is more closely related to the Bornean orang­utan than it is to the Suma­tran orang­utans liv­ing fur­ther north, in and around the Leuser Ecosys­tem, in Aceh and North Suma­tra provinces.

Orangutan comparisonCom­par­ion between the three orang­utan species, and their evo­lu­tion­ary devel­op­ment.
Credit Batang Toru Ecosys­tem web­site.

The Batang Toru orang­utans appear to be direct descen­dants of the ini­tial orang­utans that had migrated from main­land Asia, and thus con­sti­tute the old­est evo­lu­tion­ary line within the genus Pongo. The Batang Toru pop­u­la­tion was con­nected to pop­u­la­tions to the north until 10,000 or 20,000 years ago, after which it became isolated.

Alexan­der Nater, lead author, Evo­lu­tion­ary Genet­ics Group, Depart­ment of Anthro­pol­ogy, Uni­ver­sity of Zurich, Switzerland.

The Tapan­uli orang­utan is sim­i­lar to the Suma­tran orang­utan in its lin­ear body build and a more cin­na­mon pelage than that of the more hunched Bornean orang­utan. Its hair tex­ture is frizzier, how­ever, con­trast­ing with the long loose hair typ­i­cal of the Suma­tran. It has a promi­nent mous­tache and the dom­i­nant males have flat cheek-​flanges cov­ered in downy hair. The flanges dis­played by older dom­i­nant males are more like those of the Bornean orang­utan, but unlike the Bornean orang­utan, the females have beards. Fur­ther to this the Tapan­uli orangutan’s long call dif­fers from that heard in the other two species. And they eat plant species that have never been seen con­sumed by the other orang­utan species.

It is fas­ci­nat­ing that this pop­u­la­tion of orang­utans dif­fers so much from the orang­utans in the north of Suma­tra, and that even in the 21st cen­tury a new species of great ape has been dis­cov­ered” stated Dr. Ian Sin­gle­ton, Direc­tor of the Suma­tran Orang­utan Con­ser­va­tion Pro­gramme (SOCP), who has worked on improv­ing pro­tec­tion of the Tapan­uli orang­utans and their habi­tat since 2005.

Batang Toru EcosystemBatang Toru Ecosys­tem with three habi­tat sec­tions where Tapan­uli orang­utans live.
Credit Batang Toru Ecosys­tem web­site.

Tapan­uli orang­utans are now only found in the Batang Toru Ecosys­tem in the North, Cen­tral and South­ern dis­tricts of Tapan­uli, in the province of North Suma­tra, south of Lake Toba. This small rem­nant pop­u­la­tion of Tapan­uli orang­utans sur­vives in only about 1,100 km2 of remain­ing habi­tat. Min­ing con­ces­sions, a pro­posed hydro­elec­tric dam, human encroach­ment, and ille­gal log­ging all con­tinue to threaten the Tapan­uli orangutan’s habi­tat, and hence the exis­tence of the new species.

With less than 800 indi­vid­u­als left, and the pop­u­la­tion already divided over three for­est blocks sep­a­rated by roads and agri­cul­tural land, urgent con­ser­va­tion efforts are needed now to ensure the sur­vival of the Tapan­uli orang­utan. “Despite only just now being described, with so few indi­vid­u­als left, the Tapan­uli orang­utan is already the most endan­gered great ape species in the world” said Matthew Nowak, co-​author of a recently pub­lished ‘Pop­u­la­tion Habi­tat Via­bil­ity Analy­sis for Orang­utans’. “Orang­utans repro­duce extremely slowly, and if more than 1% of the pop­u­la­tion is lost annu­ally this will spi­ral them to extinc­tion”, added Prof. Dr. Serge Wich of the Sec­tion on Great Apes of the IUCN/​SSC Pri­mate Spe­cial­ist Group, that pro­vi­sion­ally clas­si­fied this new species of orang­utan as Crit­i­cally Endangered.

We have worked with the local gov­ern­ments in Tapan­uli since 2005 to social­ize the var­i­ous envi­ron­men­tal ser­vices that the Batang Toru Ecosys­tem pro­vides for local com­mu­ni­ties liv­ing near the for­est, and their liveli­hoods, and in 20014 the Gov­ern­ment finally granted pro­tec­tion sta­tus to most of the for­est”, stated Burhanud­din, who focuses on com­mu­nity aware­ness and local stake­holder rela­tions for the SOCP.

Tapan­uli Orang­utan Infor­ma­tion video

We now need to focus on recon­nect­ing the three remain­ing key pop­u­la­tions of the Tapan­uli orang­utan through cor­ri­dor devel­op­ment. The most crit­i­cal habi­tat area for the species, with the high­est den­si­ties of orang­utans, is not cur­rently pro­tected in any way, and in fact is actu­ally sched­uled for devel­op­ment of a large new hydro­elec­tric dam. And don’t for­get this is an area with one of the high­est earth­quake den­si­ties in Suma­tra”, empha­sised Kus­nadi, newly elected Chair­man of the Suma­tran Orang­utan Con­ser­va­tion Forum (FOKUS).

For sure there a lot of work to be done to make sure we the Tapan­uli orang­utan does not go extinct in the same cen­tury in which it is first described, but I am con­fi­dent that with close col­lab­o­ra­tion with the Indone­sian Gov­ern­ment, and espe­cially with local stake­hold­ers, we can make this joy­ful news a con­ser­va­tion suc­cess story”, added Dr. Gabriella Fredriks­son, who has coor­di­nated the SOCP’s con­ser­va­tion efforts in Tapan­uli since 2006.

Some quick facts about Tapan­uli orang­utan and their habi­tat:
  • Less than 800 indi­vid­u­als remain in the wild;

  • They are only found in the Batang Toru Ecosys­tem, in all three sub­dis­tricts of Tapan­uli, North Sumatra;

  • In total, the Batang Toru Ecosys­tem com­prises 150,000 hectares, with just 110,000 (1,100 km2) of this as cur­rent orang­utan habitat;

  • Approx­i­mately 85% of the Batang Toru Ecosys­tem is listed as ‘Pro­tected For­est’, with the remain­ing 15% of pri­mary for­est area listed as ‘Other Use Area’ or ‘Log­ging Forest’;

  • Most of their remain­ing habi­tat is above alti­tude of 850m;

  • Re-​establishing con­nec­tiv­ity between these three sep­a­rated pop­u­la­tions is key to the sur­vival of the species, by avoid­ing inbreeding;

  • Tapan­uli orang­utans are very slow to breed, with females hav­ing their first off­spring at around 15 years of age, with the inter­birth inter­val there­after being approx­i­mately 89 years. They can live until 5060 years of age;

  • This new species is now the rarest and most threat­ened species of great ape in the world (even rarer than the moun­tain goril­las of Africa);

  • The Tapan­uli orang­utan will be included in the IUCN Red List with an imme­di­ate entry as ‘Crit­i­cally Endangered’.

(Source: SOCP press release, 02.11.2017; Cell Press pub­lic release via EurekAlert!, 02.11.2017; MONGABAY news release,02.11.2017; Batang Toru Ecosys­tem web­site species infor­ma­tion)

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