Borneo's Rainforest: Tracking Orangutans in the World's Oldest Jungle

Borneo is the third-largest island in the world and home to one of the oldest and most biodiverse rainforests on Earth. The forest has been evolving continuously for 140 million years — it predates the Amazon by tens of millions of years — and the result is an ecosystem of extraordinary complexity and richness. The island is divided between three countries: Malaysia (the states of Sabah and Sarawak), Brunei, and Indonesia (the province of Kalimantan), and the forest spans all three territories, though deforestation for palm oil plantations has reduced its extent dramatically in recent decades.

The Kinabatangan River in Sabah is one of the best places in the world to see wildlife from a boat. The river winds through a corridor of protected forest between oil palm plantations, and the animals that remain in this corridor — orangutans, pygmy elephants, proboscis monkeys, saltwater crocodiles, and dozens of bird species including the rhinoceros hornbill — are concentrated in a relatively small area, making sightings almost guaranteed. Dawn and dusk boat trips are the most productive, when the animals come to the river to drink and the light is at its most beautiful.

The Sepilok Orangutan Rehabilitation Centre, near Sandakan in Sabah, was established in 1964 to care for orphaned and injured orangutans and prepare them for release back into the wild. The centre's feeding platforms, where semi-wild orangutans come twice daily to supplement their forest diet, offer close-up views of these extraordinary animals — the most intelligent of the great apes after chimpanzees and humans, with a cognitive ability that includes tool use, problem-solving, and a rudimentary theory of mind.

The proboscis monkey, found only in Borneo, is one of the most distinctive primates in the world. The males develop enormous pendulous noses that can reach 17 centimetres in length — a feature that appears to be a sexual selection trait, with females preferring males with larger noses. The monkeys live in groups along rivers and mangrove coasts, and their loud honking calls carry across the water. They are strong swimmers and will leap from trees into rivers to escape predators — a behaviour that is startling to witness.

The Danum Valley Conservation Area in Sabah protects 438 square kilometres of primary lowland rainforest — one of the last large tracts of undisturbed forest in Malaysian Borneo. The Borneo Rainforest Lodge, the only accommodation within the conservation area, offers guided walks through the forest with naturalists who can identify the tracks, calls, and signs of animals that are rarely seen directly. Night walks reveal a different world: flying squirrels glide between the trees, civets hunt along the forest floor, and the eyes of sleeping birds reflect the torchlight from the branches above.

Mount Kinabalu, at 4,095 metres the highest peak in Southeast Asia, rises from the rainforest of Kinabalu National Park in a series of granite ridges and pinnacles that support an extraordinary range of ecosystems from tropical rainforest at the base to alpine scrub near the summit. The mountain is home to over 600 species of fern, 326 species of bird, and more than 100 species of mammal, including the Kinabalu giant red leech, which can reach 30 centimetres in length. The two-day climb to the summit is one of the most popular trekking routes in Southeast Asia.

The deforestation of Borneo for palm oil plantations has been one of the most significant environmental disasters of the 21st century, reducing the island's forest cover from 75 percent in 1985 to around 50 percent today and pushing the orangutan, pygmy elephant, and Sumatran rhinoceros toward extinction. Choosing certified sustainable palm oil products, supporting conservation organisations working in Borneo, and visiting responsibly — staying in eco-lodges, hiring local guides, and avoiding operators that exploit wildlife — are the most direct ways that travellers can contribute to the protection of what remains.