How Many Orangutan Species Are There? All Three Explained

From one species to three

For a long time all orangutans were treated as one species. Scientists had noticed differences between the apes of Borneo and Sumatra since the 19th century, but they were usually classed as two subspecies. Genetic studies in the 1990s showed that the two island populations had been separated for a very long time, and by the early 2000s most scientists recognized them as two species, the Bornean and the Sumatran orangutan.

The third species came as a surprise. An isolated group of orangutans south of Lake Toba in North Sumatra was first reported in 1939 and found again by researchers in 1997. In November 2017, a team led by Alexander Nater published evidence from skulls, teeth, calls, behavior and the genomes of 37 orangutans showing that this population was a distinct species, which they named the Tapanuli orangutan. It was the first new great ape species described since the bonobo in 1929.

The three orangutan species compared

Bornean orangutan

The Bornean orangutan is the most numerous and widespread species. It has three subspecies in different parts of Borneo: northwest (Sarawak and northern West Kalimantan), central (southern West and Central Kalimantan) and northeast (East Kalimantan and Sabah). It has the darkest, coarsest hair, and flanged adult males have large, fleshy cheek pads and a big throat sac.

Bornean orangutans are the most solitary orangutans and, perhaps because Borneo has no tigers, they come down to the ground more often than the Sumatran species. They also rely more on bark and leaves when fruit is scarce.

Sumatran orangutan

The Sumatran orangutan lives in the northern tip of Sumatra, mostly in the Leuser Ecosystem. It is slimmer than the Bornean orangutan, with longer, paler hair and a longer face, and adult males often have long beards. It is the most sociable orangutan: several animals often feed together in large fig trees.

Sumatran orangutans in swamp forests such as Suaq Balimbing are famous for tool use, poking sticks into tree holes for insects and honey and using sticks to remove seeds from spiny fruit. They live alongside Sumatran tigers and very rarely come down to the ground.

Tapanuli orangutan

The Tapanuli orangutan is restricted to about 1,000 km² (390 sq mi) of upland forest in the Batang Toru area, at elevations of roughly 300–1,300 m (980–4,300 ft). It looks more like a Sumatran orangutan in build and color, but has frizzier hair, a smaller skull and a flatter face. Its long calls are distinctive too: they reach a higher pitch than those of Sumatran males and last longer, with more pulses, than those of Bornean males. Its diet includes unusual foods such as caterpillars and conifer cones. Researchers did not see Tapanuli orangutans come down to the ground in more than 3,000 hours of observation, probably because tigers also live in their forest.

With fewer than 800 animals, it is the rarest great ape on Earth. Its small, fragmented range is threatened by roads, farming, mining and a hydroelectric project. Read more in why are orangutans endangered?

Which orangutans are most closely related?

Surprisingly, the Tapanuli orangutan is more closely related to the Bornean orangutan than to its Sumatran neighbor. Genetic evidence suggests that the oldest split in the orangutan family tree happened around 3.4 million years ago, between the ancestors of today’s Sumatran orangutans and the line leading to the Tapanuli and Bornean orangutans. The Tapanuli and Bornean lines then separated roughly 670,000 years ago.

Researchers think the Tapanuli orangutans live close to where the first orangutans arrived in Sumatra from mainland Asia, when low sea levels during ice ages joined Sumatra, Borneo, Java and the mainland into one landmass called Sundaland.

Were there other orangutan species in the past?

Yes. Fossil teeth show that orangutans once ranged across mainland Southeast Asia and southern China, and several extinct species of Pongo have been named from fossils, including Pongo weidenreichi from China. Orangutans belong to the subfamily Ponginae, which also included the giant extinct ape Gigantopithecus. Today the three living species are the only survivors of this group. For their range today, see where do orangutans live?