20 Dec 2017

A team of researchers have shown that an isolated population of orangutans from Batang Toru, Sumatra, is distinct from other Sumatran and Bornean orangutans described so far.

The study recently published in Current Biology compared the cranio-mandibular and dental characters of an orangutan from Batang Toru, killed in a human-wildlife conflict, with 33 other adult male orangutans and found consistent differences between them. The individual from Batang Toru presented significant morphological differences such as for example a shorter tympanic tube and a narrower maxillary incisor row.

Using a genomic approach, the scientists also analysed 37 orangutan genomes backing up their conclusion that this individual belongs to a separate species which they named Pongo tapanuliensis, the likely ancestor of the two other species (Pongo abelli and Pongo pygmaeus).

This new species encompasses the Batang Toru population of orangutans ‘of which fewer than 800 individuals survive’ making it the least numerous of all great ape species according to the researchers.

Catherine Barton, Field Conservation Manager at Chester Zoo, says:

It is very exciting that a new species of great ape has been discovered but the fact that the species is at such low numbers is incredibly worrying. We need to continue to work together to find solutions to these challenges to protect all species of orangutans in Borneo and Sumatra.

Catherine Barton, Field Conservation Manager

The combination of its small population size and its geographic isolation makes the newly described species at risk of extinction due to potential inbreeding isolation. External threats affecting the ape involve road construction, illegal clearing of forests, hunting, killings during crop conflict and trade in orangutans.

Dr Yenny Saraswati, a member of Chester Zoo led Orangutan Veterinary Advisory Group and the Veterinary Manager for the Sumatran Orangutan Conservation Programme, explains:

The population of Pongo tapanuliensis is split into two major areas by the Sumatra fault valley and there is also a small population in the Sibual-buali Nature Reserve in the southeast of the western bloc.

Approximately 85% of the Batang Toru ecosystem is classified as ‘Protected Forest’ or ‘Nature reserve’ but unfortunately, the most important forest area with the highest number of Pongo tapanuliensis is classified as Other Use Areas (APL).

Yenny adds:

“This means that the area has a very low priority for protection by government. Protecting this area is crucial to rebuilding areas that can connect the currently fragmented population, to avoid intercrossing which could threaten the survival of the orangutan.”

These threats are also affecting Sumatran and Bornean orangutans across Indonesia and Malaysia putting numerous species at risk. We are working on the ground in Sabah, Malaysia, with our partner HUTAN to develop solutions to counter the effect of habitat fragmentation and deforestation and reconnect the fragmented landscape.

Our support includes reforestation activities, orangutan ecology research and the erection of orangutan bridges to facilitate the movement of these Critically Endangered primates.

Currently, the expanding unsustainable palm oil industry is one of the biggest threats facing the region where we are working. However, getting rid of palm oil completely is not a solution as many local communities rely heavily on palm oil for their livelihood.

This is why we are fully committed to supporting the market transformation to a fully sustainable palm oil supply to help reduce the industries impact on the environment without removing a crucial source of revenue for locals.

We are creating a demand in the UK for sustainable palm oil through our Sustainable Palm Oil Challenge and we have recently launched a new project working to make Chester a Sustainable Palm Oil City.  We’re encouraging more businesses in the region to sign up to this challenge.  Through our palm oil campaign, we are celebrating the companies who are already committed to 100% Roundtable on Sustainable Palm Oil (RSPO) certified sustainable palm oil, supporting those that want to be sustainable and making it easier for people to choose sustainable palm oil products.