Phone: +61 409 162 946
Imagine. Witness. Explore.

Published: 02-Jul-2020

Written by: Carly Day

Trekking in the jungle is an experience you will never forget. Each trek is unique - even if you go via the same route two days in a row there will be different animals to see, and hundreds of things you didn’t notice the day before! For me, being in the jungle is about the whole sensory experience – I could go a whole week in the rainforest without seeing any animals and still be completely besotted, rejuvenated and satisfied with my experience. It’s about the smells of earth, exotic blooms, fresh rain; it’s about the thousands of hues of green surrounding you, and the trees higher than you could imagine; it’s about the distant sound of animals calling, the sudden rumbling of thunder in the afternoon, and the extraordinary sensation when you finally dive into that river or jump under that waterfall to wash away the heat of the day. 

Because RAW is truly eco-friendly organisation we cannot guarantee that you will see any of the following animals during your trek, but with our incredibly experienced, eagle-eyed guides, you will more likely than not come across one, if not more, of these spectacular creatures when trekking in the Sumatran jungle.


There are 9 species of hornbill birds in Sumatra – and more further afield in Africa, Asia and Melanesia.

They are aptly named for their large, long, curved bill, which can be vividly coloured. What makes them unique is also what makes them highly endangered – the casque on the upper beak of most species is what these gorgeous birds are hunted for, and many species are in massive decline due to the trade in hornbill “ivory”. They are also disappearing rapidly due to habitat loss from palm oil and rubber plantations.

Known as the “farmers of the forest”, these birds are so important for spreading seeds from the specialist fruits that only they can eat with their tough bills - they eat around 750 different species of tropical plants!

Before you see a hornbill you will likely hear it. Their calls are very distinctive (and different between the species.) Our guides can identify each species purely by their calls. The larger hornbill species, such as the rhinoceros hornbill can also be heard purely by their wingbeats as they swoop across the rainforest canopy – once you’ve heard that jaw-dropping sound, which has to be witnessed to appreciate, you will always be able to identify what is flying overhead.

Two of the most likely species you’ll see during a jungle trek are:

Rhinoceros Hornbill (Boleros rhinoceros), one of the largest species weighing in between 2 and 3 kgs. These birds have a mainly white beak and a bright orange and yellow casque. The body is mostly black with a white belly and tail.

Helmeted Hornbill (Bueros vigil) is smaller in body, but longer than the rhinoceros. It has dark red skin on the sides of the head, throat and neck, whereas the plumage is black with white underparts. The casque is short and rounded: red with a yellow tip.


Gibbons are in fact not monkeys, but apes (usually referred to as “lesser apes.”) They differ from the great apes by being smaller, have less difference between males and females and, unlike the great apes, they don’t make nests, instead preferring to sleep in the crooks of trees and branches. Gibbons also tend to be monogamous, having the same mate for life, unlike the more free-loving great ape species. You’d be hard pushed to keep up with a gibbon in the rainforest – they are specialists in brachiation, which is their method of swinging from branch to branch – and are incredibly agile. If they don’t want you to catch up with them they’ll be out of sight in seconds! 50% of their diet is fruit, but leaves make up nearly a third of their diet also. The music of the gibbon singing is one of the most distinctive and memorable sounds you will hear during your jungle trekking – family groups sing in the morning and late afternoon and their gorgeous hooting melodies (used to establish and maintain family bonds and announce territory) will stay with you forever.

Most commonly during our treks you will come across one of two species:

White handed/Lar gibbon (Hylobates lar)

With a bushy coat that can vary from dark brown to a light sandy colour, these adorable gibbons have white feed and a white ring of hair around their face. Males and females can be all colours. Their calls tend to be more wavering and high pitched than the larger Siamang gibbon.

Siamang gibbon (Hylobates syndactylus)

The siamang is the largest species of gibbon in the world, and can be twice the size of the other gibbon species. With thick, glossy black hair, both males and females have what is called a “gular sac”; this is a balloon-like throat pouch that can be inflated to the same size as their head and helps their calls to be loud and resonant. Their favourite forest food is figs, and they can be found hanging out in the large rainforest ficus trees during fruiting season.

Thomas Leaf Monkey (Presbytis thomasi)

Named “The Funky Monkey” by our guides due to their awesome Mohawk hair-dos, these adorable grey and white (juveniles are pure white) primates can be found throughout the jungle, in the community gardens, and if you’re lucky, on the outskirts of some of the villages you stay in during your RAW tour. They live in troupes numbering between 20-40 individuals, and their diet is almost 50% fruit and 50% young leaves.

You may also encounter a similar looking monkey called the silvery lutung, or silvered leaf monkey – you can tell the difference by looking at the hair – silvery lutungs are completely grey/silver.

Sumatran Orangutan

Of course when we talk about the Sumatran rainforest, we can’t go past that beautiful red cousin of ours (they share 97% of our DNA) the Orangutan. One of only two species in the world, these gentle people of the forest (orangutan literally means forest person in Malay and Indonesian) have become ambassadors and the poster child for forest destruction in Indonesia. They are critically endangered due to the palm oil industry.

Orangutans are the only solitary ape, but you may be lucky enough to see a mother hanging out with her baby and/or older offspring, or a big male hanging around some females.

Spotting an orangutan in the jungle isn’t easy – their reddish orange hair somehow blends in perfectly and they move virtually silently through the rainforest canopy. Tell-tale signs of their presence are the snap of a branch overhead or the rustle of leaves, or husks and skins of fruit on the ground. You will easily spot one of their elaborate, large nests up above, but more often than not it will be vacant. Some areas are more easy to come across them than others but the same rules apply as for all rainforest species: observe, don’t touch, don’t feed, respect them from a distance and just be grateful that they let you see them at all – because trust me, if an orangutan doesn’t want you to see him or her, there’s no way you will!


These guys deserve a mention because you are likely to see them during your jungle trek at some point, whether caving, going on an evening trek, or even zipping around the outdoor light of your accommodation at night time.

Sumatra has dozens of different bat species (estimates suggest between 60 and 80 distinct species), and due to lack of research it’s hard to pinpoint the exact ones you’ll see, but if you venture into a cave system you’re likely to bump into some of the microbats such as the roundleaf or horseshoe species – these tiny insectivorous bats live in large colonies and use echolocation to both for navigation and hunting.

Horseshoe bats are named for their tiny horse-shoe shaped bumps on their noses, and roundleaf, for leaf shaped protuberances. These bats are not only super cute, but they play an important role in insect control – a single bat (dependent on the species) can eat between 600-1000 insects per hour, helping to keep the mosquito and pesky fly populations under control. When visiting bats in their cave homes, remember to keep your voices low and avoid shining torches in their sensitive eyes!

The larger megabats have fully developed eyes and rely less on echolocation as they eat nectar, pollen and fruit – making them essential in the process of pollination. Fruit eating bats and flying foxes tend to roost in large colonies in trees. Unfortunately, these are the bats you are likely to see on the side of the road throughout North Sumatra, packed into tiny cages, sweltering in the heat of the day. Some people believe that these bats can cure asthma and they are vigorously hunted for sale.

Honourable mentions

The great argus (simply called a peacock by our jungle guides).

Not your typical vibrant peacock, but stunning nonetheless – you will be sure to hear the calls of this bird throughout your rainforest trek, and come across their display areas – circular patches of cleared and cleaned ground where the male dances a display for the female.


These cheeky monkeys are common all over the place, whether it be community gardens, the side of the road, or deep in the jungle! Long tailed and pig tailed macaques are most common – and you will hear their squeals and vocalisations before you see them. In some tourist areas you need to ensure your bag is secured and you aren’t carrying any food or drink, as they won’t hesitate to steal tasty morsels from you!

Sumatran tiger

One of the most elusive rainforest animals, you are highly unlikely to directly encounter this critically endangered big cat; even our guides have never come across one in person. But if you’re lucky during a trek you may see footprints, scratch marks or other tell-tale signs of this beautiful animal.


Ok, you got me, not an animal, but magnificent nonetheless! If you’re lucky to be in the right place at the right time you’ll be able to check out one of the largest flowers in the world (the largest known weighed in at a whopping 11kgs!) Also known as the corpse flower, due to a rather pungent aroma, this is one of the rarest plants in the world.


For more information on our travel packages to North Sumatra, please visit our Indonesian Tour webpage.

Carly Day is a Raw Wildlife Encounters - Wildlife Leader and writer now based in Indonesia. With 12 years of experience working with primates, she is now exploring South East Asia and working with a variety of organisations on conservation and animal welfare. Follow her travel adventures on her blog at Carly Day .



Raw Wildlife Encounters

Get the latest travel stories, travel deals & inspiration straight to your inbox.

Join our Raw Community!

Subscribe to: _newsletter (form) Subscribe to: _Receive eNews
  • Sri Lanka Image Sri Lanka
  • Africa Africa
  • Malaysia Malaysia
  • Mongolia Mongolia
  • Indonesia Image Indonesia
© RAW Wildlife Encounters, T/A 32907. All rights reserved.