Population & distribution
Orang-utans were once distributed widely across Southeast Asia, roaming as far north as southern China, and as far south as the Indonesian island of Javar. But today Asia's great ape is confined to just two islands, Borneo and Sumatra.
As the orang-utan's range has decreased so have its numbers. A century ago, there were probably 230,000 orang-utans - around four times as many as there are today.
Their dense forest home makes it difficult to determine population sizes, but the Bornean orang-utan is estimated to number around 104,000 individuals, while there are under 14,000 Sumatran orang-utans.
The Sumatran orang-utan is now restricted to the north of Sumatra. It depends on high-quality primary forests, and is less able to tolerate habitat disturbance than Bornean orang-utans. Sumatran orang-utan densities reportedly fall by up to 60% with even selective logging.
The population is currently fragmented into 13 populations in 21 forest blocks. Only 6 of these populations boast more than 250 animals and are therefore regarded as viable in the long term, but even these groups are under threat due to ongoing habitat loss.
The Bornean orang-utan was once distributed throughout large areas of Kalimantan (Indonesia) and Sarawak and Sabah (Malaysia) on the island of Borneo. But its population has fallen by more than 50% over the past 60 years, while at least 55% of its habitat has disappeared over the last 20 years.
Most Bornean orang-utans are now found in Kalimantan, especially along the east coast. The majority of wild populations are located outside of protected areas, in forests that are exploited for timber production or are in the process of being converted to agriculture.
Three subspecies live in different parts of the island:
- Northwest Bornean orang-utan is the most threatened subspecies with over 3,000 remaining.
- Northeast Bornean orang-utans are the smallest in size. Around 16,000 live in Sabah and parts of eastern Kalimantan.
- Central Bornean orang-utans are the most common subspecies with around 35,000 surviving.
What are the main threats?
is by far the greatest threat to orang-utans. Huge tracts of forest have been cleared throughout their range and the land used for agriculture, particularly palm oil - a product that is found in more than half of packaged products in supermarkets around the world.
Road development, illegal timber harvesting and unsustainable logging, mining and human encroachment also contribute to habitat loss, degradation and fragmentation.
Today, more than 50% of orang-utans are found outside of protected areas, in forests under management by timber, palm oil and mining companies.
But even protected areas are not secure since the boundaries of protected areas in Borneo are often not clearly delineated, which makes them difficult to patrol. Furthermore, many parks are understaffed and underfunded. Consequently, oil palm companies and logging firms have encroached into all the parks.
Along with habitat loss, young orang-utans up to the age of seven are sought after for the illegal pet trade.
When infants are targeted, usually the mother is killed so this trade represents a real threat to wild orang-utan populations.
In addition, orang-utans are hunted in some areas
for food. They are also sometimes killed
when they move into agricultural areas and destroy crops.
And fire is also a major threat. In 1997-98, the drainage of peat-swamp forest contributed to uncontrollable fires
in Kalimantan, which lasted for 6 months and killed up to 8,000 orang-utans.