A 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.
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.
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.
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 8 – 9 years. They can live until 50 – 60 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’.