A vitally important genetic resource and wildlife habitat, Gunung Leuser National Park, is part of the 2.6 million hectare Leuser Ecosystem and houses some 130 mammal species including 8 primate species, 285 species of birds, among them the Rhinoceros Hornbill and 89 endangered and protected species including the Sun Bear, gibbon,Sumatran orangutan, Sumatran elephant and the very rarely seen Sumatran tiger and Sumatran rhino.

Bohorok Orangutan Rehabilitation Centre, Bukit Lawang

In 1973, the orangutan rehabilitation centre was set-up by a Swiss organization in Bukit Lawang, to rehabilitation of those orangutans rescued from poachers or deforestation.

During their stay at the centre, these orangutans are taught all the necessary survival skills they need to be successfully reintegrated into the jungle as part of the semi-wild population.

On release, they are monitored by rangers and provided with supplementary food at the feeding platform until they become fully self-sufficient.

What animals are you likely to see at Gunung Leuser?

You are most likely to see semi-wild orangutans, macaques, pig-tailed macaques, the Thomas’ Leaf monkey and his amazing ‘quiff’.

Wild orangutans are harder to spot and you will need to venture deeper into the jungle to see them.

If you’re lucky, you may see hornbills or even white and black gibbons (most likely you will hear their distinctive calls), moon snakes or monitor lizards gliding in and out of the river.

Rarer still is an encounter with either the Sumatran Tiger or the Sumatran Rhinoceros. Few remain in the wild and are sensibly reclusive, although footprints and droppings have been reported.

A day trip to Tangkahan or a longer trek deep into the jungle near Ketambe is a must if you would like to see the Sumatran elephant in the wild.

While seeing creatures in the wild is never guaranteed, visitors can immerse themselves in their habitat and experience their environment while they wait to catch that elusive glimpse of their favourite animals.


Sumatran Orangutan

Sharing 96.4% of our DNA, ‘Orang Hutan’ literally meaning ‘Person of the forest’, are highly endangered due to habitat loss and poaching.

Found in Sumatra, the Sumatran orangutan looks slightly different to its Bornean relatives with lighter hair, a longer beard and narrower cheekpads (males).

Arboreal fruit eaters, they live in the forest canopy, spending up to 60% of their time foraging, eating and building nests in the trees.

Solitary creatures, a large family unit will tend to consist of a female and two offspring. Infants will tend to stay with their mothers for at least their first five years; so on average a female will have a baby every 7-8 years and no more than 3 in her lifetime (they live for around 45 years).

Highly intelligent and gentle, orangutans have excellent memories, remembering the location of fruiting trees throughout the year.

Help protect the orangutan.



Sumatran Tiger

Found only on the island of Sumatra, the Sumatran tiger is the smallest tiger in the world, with males rarely growing to 2.5 metres in length.

Found in a variety of habitats from low and highland areas, to mountainous jungle and peat swamp forests, Sumatran tigers are solitary, generally only coming together to mate.

Narrower stripes, larger manes and slightly webbed feet characterise their appearance.

Critically endangered due to poaching and loss of habitat, it is estimated that as few as 400 remain in the wild.


Sumatran Rhinoceros

The smallest of the rhino family (weighing up to 950kg), the Sumatran rhino has two horns (a long front horn and smaller rear horn), long fur covering its body, and a reddish brown skin colour.

Eating more than 50kg of food each day, these herbivorous mammals feed on fruit, leaves, twigs, and bark and prefer lower altitudes, especially secondary forests where low-growing plants are more abundant.

Living to around 35-40 years, females will give birth to one calf every 3-4 years and these calves will live with their mother for 16-17 months before taking up a solitary lifestyle.

Critically endangered, fewer than 100 Sumatran rhinos are thought to be left in the wild, making the Sumatran rhino one of the rarest large mammals in the world.


Kukang Sumatra (Greater Slow Loris)

Known to inhabit the lowland tropical rainforest of Sumatra, the Greater Slow Loris is reddish in colour with huge eyes and toxic canines.

Nocturnal and arboreal, measuring 27-38cm from head to tail, they can live up to 22 years on an omnivorous diet of fruit, stems and bark, arthropods (like spiders), nectar, snails, and bird eggs.

Solitary creatures, a group may consist of a pair of adults and 1-3 young.

Listed as vulnerable, they are threatened with extinction due to growing demand in the exotic pet trade and deforestation of their habitat.


Thomas’ Leaf Monkey


The Thomas’ Leaf monkey is distinguishable by its black and white fur and distinctive black mohawk hairstyle.

Primarily leaf eaters, they can live up to 20 years, in single-male/multi-female groups, in primary and secondary rainforest and rubber and fruit plantations.

Found in Northern Sumatra, the population of the Thomas’ leaf monkey is decreasing due to loss of primary habitat as a result of logging and conversion to palm plantations. They are protected by Indonesian law.


Corpse flower (Amorphophallus Titanium/Titan Arum)

First discovered in Sumatra in 1878 by Italian botanist Odoardo Beccari, the ‘Suweg Raksasa’ is endemic to Western Sumatra where it grows on steep hillsides in the rainforest.

Famous for its pungent smell which attracts pollinators, it blooms rarely (every 7 years) and only for a short time (12 hours).

An inflorescence-a stalk with many flowers, the corpse flower can grow to a massive 2.4m tall.

Classified as vulnerable, the corp flower is becoming increasingly rare as a result of deforestation, pollution and farming.