Discover the fascinating world of flanged orangutans in Borneo. Learn about their cheek pads, unique behaviors, and how they differ from unflanged males. Explore the three species of orangutans found in Southeast Asia and why conservation is crucial.
Orangutans are among Southeast Asia’s most captivating primates, admired for their intelligence, tool use, and gentle personalities. In the wild rainforests of Borneo and Sumatra, one subgroup stands out—the flanged orangutan, instantly recognizable by its broad cheek pads and larger build.
For a long time, scientists thought there were only two species of orangutans. But recent research confirmed a third species, making it three in total:
Bornean Orangutan (Pongo pygmaeus) – Found only on the island of Borneo (Sabah, Sarawak, and Kalimantan).
Sumatran Orangutan (Pongo abelii) – Native to the northern part of Sumatra, Indonesia.
Tapanuli Orangutan (Pongo tapanuliensis) – The rarest, with fewer than 800 individuals, discovered in 2017 in Batang Toru, Sumatra.
All three species are critically endangered due to deforestation, habitat loss, and illegal hunting.
A flanged orangutan is an adult male that has developed:
Large cheek pads (flanges) made of fatty tissue
A throat pouch for booming long calls
Longer hair around the shoulders and neck
A bigger, more muscular build
These features announce maturity and dominance, helping them claim territory and attract mates.
| Feature | Flanged Male Orangutans | Unflanged Male Orangutans |
|---|---|---|
| Cheek Pads | Wide, fleshy flanges | Smooth, no flanges |
| Body Size | Larger, more robust | Smaller, slimmer build |
| Throat Pouch | Present, amplifies calls | Absent |
| Hair Length | Long, shaggy mane | Shorter hair |
Fun fact: Both are sexually mature males—but only some develop flanges due to hormones and social dynamics.
Territorial Calls: Long, booming calls resonate across the forest, warning rivals and attracting females.
Dominance Displays: Size, vocal power, and flanges help them maintain alpha status.
Mating Rights: Flanged males usually dominate reproduction, though unflanged males may sneak in.
Protective Instincts: While solitary, flanged males may sometimes guard females and young when nearby.
The dramatic cheek pads serve multiple purposes:
Sexual Selection: Females often prefer males with strong flanges, associating them with good genes.
Social Status: A natural “badge of dominance” to intimidate rivals.
Hormones at Work: Flanges develop as testosterone rises, but not all males experience this transformation.
In Sabah’s wild corners—Danum Valley, Kinabatangan River, and Sepilok—lucky visitors may spot these magnificent males swinging through the canopy or calling across the rainforest. Conservation centers, like the Sepilok Orangutan Rehabilitation Centre and the Bornean Sun Bear Conservation Centre, play a vital role in ensuring their survival.
While Sabah offers some of the best chances to see these cheek-padded giants, they’re also found in other parts of Borneo and Sumatra:
Sarawak, Malaysian Borneo – Sanctuaries like Semenggoh Wildlife Centre near Kuching provide opportunities to observe semi-wild orangutans up close, including impressive flanged males during feeding times.
Kalimantan, Indonesian Borneo – Home to vast orangutan habitats such as Tanjung Puting National Park, where boat safaris along the Sekonyer River often reward visitors with sightings of dominant flanged males.
Sumatra, Indonesia – The Gunung Leuser National Park, part of the Leuser Ecosystem, is the stronghold of the Sumatran orangutan. Treks here sometimes reveal powerful flanged males guarding their forest territories.
Batang Toru, Sumatra – The only place in the world to see the extremely rare Tapanuli orangutan, the third recognized species. Though sightings are incredibly limited, researchers occasionally document flanged males here.
Best Chance (High Density, Guided Access):
Danum Valley Conservation Area, Sabah (Malaysia) – World-class wildlife lodges, guided treks, and one of the richest orangutan habitats in Borneo.
Most Accessible (Easy Wildlife Cruises):
Tanjung Puting National Park, Kalimantan (Indonesia) – Famous for its houseboat river safaris, where sightings of flanged males are common.
Semi-Wild & Close Encounters:
Semenggoh Wildlife Centre, Sarawak (Malaysia) – A rehabilitation hub near Kuching with daily feeding sessions that often attract dominant flanged males.
Most Adventurous (True Jungle Trekking):
Gunung Leuser National Park, Sumatra (Indonesia) – Multi-day treks offer the thrill of spotting Sumatran flanged orangutans in their rugged rainforest home.
Rarest Species (Scientific Treasure):
Batang Toru Forest, North Sumatra (Indonesia) – The only home of the Tapanuli orangutan, the rarest great ape on Earth. Sightings are difficult and usually limited to research expeditions.
Just like most wildlife adventures in Borneo and Sumatra, timing matters. Orangutans are wild and unpredictable, but visiting during the right season boosts your chances of a magical encounter.
Sabah (Danum Valley, Kinabatangan, Sepilok)
March to October – The drier season is the best time for treks and river cruises. This also overlaps with Sabah’s peak travel season (June–August), when skies are clearer and wildlife sightings are at their best.
Sarawak (Semenggoh Wildlife Centre)
Year-Round – Feeding sessions guarantee good viewing, but April–October (dry season) makes it easier to combine orangutan watching with trekking in national parks.
Kalimantan (Tanjung Puting National Park)
June to September – Dry, sunny months make houseboat safaris comfortable and sightings more frequent. This is also the park’s busiest season, so book early.
Sumatra (Gunung Leuser National Park)
June to September – The rainforest is drier, trekking is easier, and visibility improves. This is the peak season for Sumatra travel as well, so expect more trekkers on the trails.
Batang Toru (Tapanuli Orangutan)
Not open for regular tourism – Research access only, though conservation-based tourism may open in the future.
✨ Travel Tip: Peak season (June–August) not only improves your chances of seeing flanged orangutans but also offers the best conditions for diving in Sipadan, climbing Mount Kinabalu, and exploring Sabah’s islands—making it the perfect time to plan a well-rounded Borneo adventure.