What is a Bornean orangutan?
The Bornean orangutan is one of three orangutan species on the planet, and it is native to the island of Borneo in Southeast Asia. Like other orangutans, Bornean orangutans are known for their shaggy red or orange coats that cover nearly their whole body, though their face, ears, palms, and the soles of their feet have no hair. They are also recognisable by their long arms, which are typically one-and-a-half times longer than their legs.
Orangutans have many similarities with humans, just like other great ape species, sharing approximately 97% of their DNA with us. Like humans, they have 32 teeth and wide faces with a less pronounced brow than other primates. Adult males sport prominent moustaches and beards, and all adults develop breasts once they reach maturity.
Bornean orangutans aren’t small animals. In fact, they’re the largest tree-dwelling mammals on Earth. When standing upright, fully grown adult males measure about 97 centimetres (3.2 feet) tall and weigh 60 to 90 kilograms (132 to nearly 200 pounds). Fully grown females are markedly smaller than males, standing around 78 centimetres (2.5 feet) tall and weighing just 40 to 50 kilograms (88 to 110 pounds).
The Bornean orangutan is frugivorous, meaning that the majority (roughly 60%) of its diet is made up of fruit—wild figs and durians are their favourites. They also eat insects, leaves, shoots, and other plant matter. Orangutans, as well as other great apes, are also known to eat rocks and soil to get nutrients that are lacking in their food.
These primates are found exclusively on the island of Borneo, mostly in the rainforest, where they make their homes among the tree canopy. As largely solitary animals, Bornean orangutans aren’t known for forming social groups. Instead, they spend their days alone, travelling through the tree canopy with occasional breaks to nap and eat. However, they’re not territorial or antisocial and are known to be cordial with other orangutans they encounter in the wild.
Female orangutans reach sexual maturity between the ages of 11 and 15, which is when they will mate with a fully-developed male who shares, or is nearby, their home territory. After an eight-month gestation, a female Bornean orangutan gives birth to one infant, which she nurses for six to seven years. The mother is responsible for raising the young and teaching them how to live in the wild. Orangutans are the slowest of all mammals to breed, taking a period of about eight years between producing offspring.
Bornean orangutans play an important role in their ecosystem. As their diet consists largely of various fruits, they help spread the seeds of these plants through their faeces, which bolsters plant diversity in the areas they inhabit.
What is a Bornean orangutan’s scientific name?
The scientific name for a Bornean orangutan is Pongo pygmaeus. Pongo is a 17th-century term for a large African ape, derived from Congolese. The name pygmaeus is derived from the Greek ‘pygmy’, which means dwarf.
There are three subspecies of Bornean orangutan spread across the island, and each has its own scientific name:
- The northwest Bornean orangutan is known as Pongo pygmaeus pygmaeus
- The southwest Bornean orangutan is known as Pongo pygmaeus wurmbii
- The northeast Bornean orangutan is known as Pongo pygmaeus morio
Are Bornean orangutans endangered?
Since 2016, Bornean orangutans have been classified as critically endangered with a decreasing population trend, which doesn’t bode well for the survival of the species.
From 1950 to 2010, Bornean orangutan populations decreased by more than 60% and a further 22% decline is projected between 2010 and 2025. This is a loss of over 82% of the entire species in just 75 years.
Where do Bornean orangutans live?
As evident from their name, Bornean orangutans live exclusively on the large island of Borneo, located in Southeast Asia and occupied by Indonesia, Malaysia, and Brunei. They inhabit the tropical and subtropical rainforests of the island, making their homes in leafy tree canopies, where they spend about 90% of their time.
Bornean orangutans are also found in forestland and swamps, but they prefer to stay in the lowlands. However, some isolated populations can also be found in highland habitats, such as in Kinabalu National Park, which is 1,500 metres above sea level.
There are three subspecies of Bornean orangutans living on the island in three distinct areas. The northwest Bornean orangutan inhabits the Malaysian state of Sarawak and the province of West Kalimantan, Indonesia. Northeast Bornean orangutans can be found in Sabah, Malaysia, as well as two Indonesian provinces, North and East Kalimantan. The southwest Bornean orangutan, which is sometimes called the central Bornean orangutan, is found only in the Indonesian provinces of West and Central Kalimantan.
Bornean orangutans face a number of threats, all of which have contributed to the steep population decline of the species over the last century. These threats come mostly from human activity on the island, plus the looming threat of climate change.
Deforestation on the island of Borneo—caused by agriculture, logging, and palm oil plantations—has increased at a staggering rate. Between 2000 and 2010, Borneo lost around 3,234 square kilometres of forest on average per year. If deforestation continues at the current rate, 129,000 square kilometres of forest could be lost on Borneo by 2050.
While some protected areas of the island cannot be developed, nearly 80% of Bornean orangutans live outside this land and are in constant danger of losing their homes. Around 30% of the habitat used by Bornean orangutans is in commercial forest reserves, which are logged for timber, and around 45% live in forest areas that are set to be converted to agricultural land. By 2025, 61.5% of orangutan habitat on Borneo will be destroyed.
Along with the threat of human development, forest fires are a huge problem for wildlife in Borneo as well.
In 1983 and 1998, two massive fires wiped out 90% of Kutai National Park. The orangutan population in this area was reduced from an estimated 4,000 individuals in the 1970s to just 600. In 1997 and 1998, a devastating fire burned through peatland forest, which resulted in the loss of around 8,000 orangutans. Another fire in 2015 burned through more than 20,000 square kilometres of forest, leading to hundreds more deaths.
Habitat destruction, caused by human encroachment and natural disasters, leads to habitat fragmentation. With less and less viable land available for orangutans, they become spread out and isolated from one another. This makes it harder for orangutans to find mates and reproduce, meaning these isolated populations are likely to go extinct. It’s thought that orangutan populations consisting of less than 50 individuals are not viable in the long term.
A massive threat faced by orangutans in Borneo is poaching. Despite strict laws being in place, several thousand of them are hunted and killed each year, either for their meat, to mitigate human-wildlife conflict, or for other reasons. The IUCN estimates that 2,383 to 3,882 Bornean orangutans are hunted per year, and poaching has contributed to 12% of their population decline over the last 75 years.
Another reason this is particularly problematic is the slow reproductive cycle of orangutans. On average, they give birth only once every eight years, so it’s impossible for new births to keep up with the mortality rate.
One of the biggest ways that poaching can be avoided is through basic education. In the Bornean state of Kalimantan, 27% of people did not know that orangutans are protected by law. To protect the critically endangered Bornean orangutans, we need to inform the public and encourage everyone to support their conservation.
Climate change is increasingly impacting animal populations around the globe. Bornean orangutans are no exception. They’ve seen a loss of 69% to 81% of their habitable land since 2010. When compared to the loss of habitat that comes from deforestation, climate change presents a three to five times greater decline.
As one of the smartest animals on the planet—and one of the most similar to humans—there is no shortage of interesting facts about Bornean orangutans.
What do Bornean orangutans eat?
The majority of the orangutan diet, around 60%, is made up of fruit. The rest of their nutrition comes from a variety of sources, mostly plants. They eat leaves, shoots, tree bark, honey, insects, and bird eggs.
Interestingly, orangutans also eat soil and rocks on occasion to get essential nutrients that aren’t found in their regular diet.
Where are Bornean orangutans found?
Bornean orangutans are native to the island of Borneo. They live mostly in lowland forest areas, preferring to live in tropical and subtropical rainforests.
There are three subspecies of Bornean orangutans, each found in a different geographical area of the island:
- The northwest Bornean orangutan inhabits the Malaysian state of Sarawak and the Indonesian province of West Kalimantan.
- The northeast Bornean orangutan can be found in Sabah, Malaysia, as well as two Indonesian provinces, North and East Kalimantan.
- The southwest Bornean orangutan—which is sometimes referred to as the central Bornean orangutan—is found in the Indonesian provinces of West and Central Kalimantan.
Do Bornean orangutans stay in groups?
Bornean orangutans are largely solitary animals and don’t tend to form groups. However, they’re not aggressive or territorial with each other. Female orangutans with a shared home range are known to pair up to forage for food.
What are the adaptations of a Bornean orangutan?
These creatures have adapted to live in the trees, where they spend 90% of their time. Their very long arms—which are 1.5 times longer than their legs—allow them to swing from branch to branch with ease, while their hook-shaped hands and feet with long fingers and toes help them grasp tightly. They have very short thumbs, which don’t get in the way while they’re swinging.
Bornean orangutans have also developed large, thick jaws, which help them to crack the skin of nuts and fruits that make up their diet.
What colour is a Bornean orangutan?
Bornean orangutans are reddish-brown. Males stand about one metre (three feet) tall, while females are about 80% of the size of their male counterparts. They have no tails, but they do have long arms that help them swing through the rainforest canopy.
Are Bornean orangutans friendly?
Yes, Bornean orangutans are largely a non-aggressive species, and they will often associate with each other peacefully, even though they are solitary animals. The only time conflict arises between Bornean orangutans is when males are fighting over territory or to mate.
However, despite them being ‘friendly’ with each other, we should never approach them—they are still wild animals.
Why are Bornean orangutans important?
This species plays an important role in their ecosystem, helping maintain plant diversity in the areas they inhabit. As their diet consists of a variety of fruit, they help spread the seeds of these plants through their faeces.
What would happen if the Bornean orangutan went extinct?
The extinction of the species would have many knock-on effects on the other plants and animals that live on Borneo. Without the orangutans spreading seeds and helping plants to grow, these plants would die out. Then, the animals that rely on those plants for food would soon also go extinct, and the entire ecosystem would struggle to survive.
What is being done to protect the Bornean orangutan?
From fighting the illegal online wildlife trade to rescuing and rehabilitating orangutans that have been captured as illegal pets, IFAW and other conservationists are working hard to reverse the decline of orangutan populations.
How many Bornean orangutans are left?
It’s hard to track the species and know exactly, but estimates place the current population of Bornean orangutans at around 100,000. That may sound like a lot, but their numbers are declining at a rapid and alarming rate.
What is the difference between Sumatran and Bornean orangutans?
These two great apes diverged from one another about 400,000 years ago. While the two used to be considered subspecies of the same species, in 1996, they were classified as two different species of great ape.
They have several differences which makes it easy to distinguish the two. Firstly, Bornean orangutans inhabit the island of Borneo, while Sumatran orangutans are found on the island of Sumatra. Bornean orangutans have also developed darker red coats and rounder faces than their Sumatran cousins.
In 2020, the IFAW-supported Centre for Orangutan Protection (COP) in Borneo took over the care of two critically endangered orangutans—a mother and daughter, Uchokwati and Mungil. Uchokwati was a victim of the exotic pet trade, likely taken from her mother as a baby, and she ended up on display in an amusement park. She was rescued in 2011 and sent to a wildlife centre, where she gave birth two years later.
Once under the care of COP, both orangutans were chosen as prime candidates for rehabilitation and release back into the wild. In April 2022, they were sent to a pre-release island and spent time acclimating to their natural surroundings. Here, Mungil climbed a tree for the first time in her life.
In late October, both mother and daughter were released into 20,000 hectares of protected land. Here, they are closely monitored by rangers to ensure they are thriving.
In January 2021, IFAW provided emergency aid to COP following a 6.2 magnitude earthquake in Indonesia. COP helped set up an animal assistance service centre, providing food and veterinary care.
In 2023, IFAW’s partners Jakarta Animal Aid Network (JAAN) and Wildlife Trust of India (WTI) rescued a ten-month-old male orangutan from online wildlife traffickers. IFAW has been a pioneer in researching and monitoring online wildlife trafficking.
IFAW has been a pioneer in researching and monitoring online wildlife trafficking.
How can you help?
Bornean orangutans face a range of threats, including habitat loss, degradation, and fragmentation, in addition to poaching and climate change.