The Sumatran Orangutan
Orangutan in Malay language means ‘Person of the forest’ (orang = 'person' and utan derived from hutan = ‘forest’ )
Orangutans are the only great ape found in Asia. They were once widespread across Southeast Asia, but now are only found on the islands of Borneo and Sumatra. They are two separate species; the Bornean Orangutan Pongo pygmaceus, which also has 3 sub species and the Sumatran Orangutan Pongo abelli. At the end of 2017, a new species of orangutan was discovered in Northern Sumatra and identified as Pongo tapanuliensis. All species are classified as Critically Endangered, with both islands suffering from huge Orangutan population declines over the last few decades. The newly discovered Tapanuli orangutan with only 800 individuals, is the rarest great ape in the world!
Sumatran Orangutan 13,846
Tapanuli Orangutan: 800
Tropical and sub-tropical forest
Bornean and Sumatran orangutan differ slightly in appearance and behaviour. Both have red – orange hair but the Sumatran Orangutan (Pongo abelii) has paler hair, is more ‘golden’ in colour and is also shorter than the Bornean orangutan. The species is sexually dimorphic, meaning they differ. Males are approximately twice the size of than females, weighing 50-90kg and females 30-50kg. There are two types of males; flanged and unflanged. Flanged males have prominent cheek pads called flanges. The Sumatran orangutan flanges are flat and extend out from the face. Both male species have a throat sac that is used to produce a ‘long call’ for attracting females which can be transmitted for several kilometers. Unflanged males look like adult females and can still reproduce, however they can change to a flanged male for reasons that are not fully understood
Orangutans have long arms, one and a half times the length of their legs, flexible shoulder joints and have opposable thumbs and big toes enabling them to grasp branches and manipulate objects.
The lifespan of the Orangutan is quite long, up to 50 years, with males generally living longer. They have the slowest life histories of all mammals, with roughly the same gestation as a human of 8.5 months and have the longest inter-birth rate of any mammal. The baby orangutan is completely dependant on its mother for the first 2 years of its life and will stay with her for up to 8 years. Females normally become sexually active at about 12 years, usually having their first off-spring at 15 years.
The Orangutan Project gives and you can read more about why Orangutan's are in crisis here
HEIGHT: males - about 1.5m; females - about 1.2m
WEIGHT: males - 93 to 130 kg; females – 48 to 55 kg
LIFE SPAN: 50 years or more
GESTATION: about 8.5 months
No. OF YOUNG: usually 1, very rarely 2
DIET: Mainly fruit, but leaves, flowers, ants, bark
Life in the Trees
Orangutans are the largest and most arboreal ape in the world, spending most of their lives in the trees. Because of this they are specialist of primary forest. Although they have large bodies, they are able to move through forest gracefully, if not a little slow. Using their long arm to grasp a branch and then grasping with their foot, they can be suspended four-limbed between two branches, swaying, before they are able to get enough motion to cross over.
They spend most of their daytime foraging for food which is found in the treetops. Sumatra Orangutans are primarily frugivores, which makes up as much as 90% of their diet, as it is a high calorie food and more nutritious for feeding their large bodies. Preferred fruits include wild figs, which the large fig trees are abundant in Sumatra. This also means that wild orangutans rarely venture to the floor, however this is slightly different to the semi-wild orangutans in Bukit Lawang which regularly come to the ground in search of dropped fruit peelings.
Every night orangutans build a new nest to sleep by breaking branches and folding the leaves together. This can be several meters above the ground. Sometimes they will makes nests midday for taking a nap or when it is raining, using a large leaf as an umbrella.
Why They Matter
They are a 'flagship' species for the conservation of the tropical forests in Sumatra. Ensuring their survival will help save the rainforests along with all the myriad of other wildlife
Orangutans are frugivores and play an important role in seed disperal.
If they were to disappear then many tree species would as well
Orangutans rely on the forest for food, as do 4 million people for water, food and natural medicines
The Sumatran forest is also home to many other spectacular species - Elephant, Tiger, Rhino, Hornbills, Sunbears
Orangutan habitat is vital for the fight against climate change, providing oxygen from its trees and carbon storage in its peat swamp forests
Orangutan habitats are important ecosytems, providing flood barriers and prevents soil erosion
Orangutans have lost over 80% of their habitat in the last 20 years, with Sumatran Oangutans now restricted to the North of Sumatra. The expansion of oil palm plantations has seen large areas of rainforest being cut down and cleared causing orangutans populations to be fragmented into several populations. However, a large population still remains in the Gunung Leuser National Park, but there are many smaller populations that live outside this protected area. The main threats to these populations is; deforestation, small-scale agriculture, illegal hunting and killing. As a an area becomes human-dominated orangutans come into conflict with humans. With less forest and food, orangutans go in search of fruits often coming onto agricultural land or private owned agfro-forest. If Orangutans frequently come and eat cash crop fruits, like Durian, local landowners see them as pests and often shoot them. Eco-tourism is one way that can provide revenue for local communities and therefore help help protect the Orangutan habitat.
Map of the Leuser Ecosystem and distribution of Orangutans in North Sumatra. Singleton, I & A.Dadi R & R. Taken from WWF
By providing responsible trekking in Bukit Lawang and as part of our Eco Sustainble Plan, we are developing and offering eco-treks in other areas bordering the national park, where wild orangutans and other threatened flora and fauna live, Sumatra EcoVentures can provide income for the local communities.
Hopefully, its ecomonic incentive will encourage local government to protect these areas. Sumatra EcoVentures encourages guests and visitors to follow the parks guidelines and we have our own strict guidelines when trekking to see Orangutans and other wildlife.
Our upcoming volunteer program to monitor and protect a small population of wild Orangutans is another way that you can help conserve Orangutans, their habitat and other wildlife and give income to local people.