The Leuser (pronounced low-ser) Ecosystem spans over 2.6 million hectares of jungle in Sumatra across the Indonesian provinces of Aceh and North Sumatra, 1 million hectares of which constitutes the Gunung Leuser National Park. Stretching along the Bukit Barisan Mountain Range with the Alas River at its centre, it's part of the UNESCO World Heritage Site known as the "Tropical Rainforest Heritage of Sumatra". Ketambe village is located in a valley at the centre of the lung shaped ecosystem. Trekking into the national park from here brings you directly into the middle of the jungle, where old growth trees reach 60m into the sky and the layers of canopy are full of biodiversity.
Most travellers venture to Ketambe in search of wild orangutans. It is one of the few remaining places in the world with a high chance of spotting completely wild (non-rehabilitated) orangutans living without human intervention. None of the orangutans here are ever fed or touched by humans. Which is why they stay up in the trees, gracefully swaying between branches.
Besides orangutans, the Leuser is also home to hundreds of other truly unique animals. There are 380 species of birds, 194 reptiles and amphibians and almost 130 species of mammals inhabiting the park. It is the only stretch of jungle left in the world where elephants, tigers, rhinos and orangutans all live together. While these large mammals are incredibly rare to see, it is possible to go on longer treks to different areas of the forest in search of them. Other animals living here that are easier to find include: hornbills, Thomas langur monkeys, long-tail macaques, pig-tail macaques, palm civets, flying lemur (colugo), butterflies, snakes, gibbons, binturong, giant squirrels, monitor lizards, owls, lantern-bugs, flying dragons, chameleons, trogon birds. If you're very lucky maybe even a slow loris, clouded leopard, sunda pangolin or mouse deer.
Trekking from Ketambe into the Gunung Leuser National Park you will find some of the most well-preserved old growth forest left in Asia. Enormous trees reach up into the clouds and liana vines as thick as your torso hang down from above. Over 4000 species of plants can be found here in Southeast Asia’s largest expanse of rainforest. The volcanic hotsprings pour out from the earth and mix with the cool river, creating completely natural warm pools where you can relax and watch the surrounding jungle envelope you. After the rain you will probably come across a few hungry leeches, but mosquitos and flies here are scarce. You may find you don't need to use insect repellent at all.
