JOSEPH Conrad spoke of the "mysterious life of the wilderness that stirs in the forest" in the novel "Heart of Darkness." On my first night in the jungle, life stirred all around and wild mysteries scuttled feverishly across my mind.

Engulfing the sagging sodden trees of the jungle floor is a deafening cacophony of howls and shrills emitted by the hordes of reptiles, insects and beasts that scurry across every inch of land.

Tarantulas are common and stand defiantly in their natural habitat. Snakes, bats, lizards and insects that defy description (so elaborate and dangerous they look to the human eye) engage in a treacherous coexistence within the entwining net of the jungle floor. Few men or women are welcome in the heart of the jungle, or equipped to deal with its numerous perils.

This is Borneo, one of the world's few remaining wildernesses. The biodiversity on the island makes nature lovers go weak at the knees - more than 200 mammals, 500 birds and fish, 100 amphibians and 15,000 plants. WWF can only estimate as to the sheer scale of life on the island.

Sabah and Sarawak form the Malaysian division of the island, which is predominantly Indonesian bar the tiny state of Brunei. A ferocious mix of cultures, beliefs, cuisines, languages, plants and animals make this an exhilarating destination. It's difficult to do Borneo justice, and I had a little under three weeks to explore the Malaysian section of the island. I barely began to uncover the secrets of this mysterious island.

The journey started at Mulu National Park in the southern state of Sarawak, brought to popular attention by David Attenborough in the BBC series "Planet Earth." The park can be accessed by a boat that leaves from the uninspiring town of Miri, but it takes a couple of days (and a considerable sum of money) to snake up the river.

A 20-minute flight is the alternative if time and resources are stretched. Mulu's caves are stupendous both in size and intricate formation, the guano droppings form putrid towers, and the wildlife is abundant. The park's highlight is the immense Deer Cave, over 2 kilometers deep and famously large enough to fly a jumbo jet through.

Home to bats

But it is also home to millions of bats that leave the mouth of the cave at dusk in a swirling doughnut-shaped swarm, which regrettably does not happen every night. Caves, canopy walks, boat rides, jungle treks - Mulu Park has it all. Plus, it protects around 52,000 hectares of wildlife from the ever-encroaching threat of palm tree plantations.

The capital city of the northern state of Sabah is Kota Kinabalu, and it features a range of tropical islands scattered just across the ocean in plain and resplendent view from the city.

The islands are easily accessible and beautiful, with opportunities to snorkel (or dive) in the bountiful reefs, or laze around on the beaches as giant monitor lizards roam sleepily around the sunbathers. The city hosts a daily open air wet market on the harbor, providing a rich array of sea life to sample barbecued as you watch the sun set over the ocean. Clean beaches, rich reef life and a party atmosphere make Kota Kinabalu a bustling spot for tourists and locals alike.

Heading by bus through the heart of Sabah you pass Mount Kinabalu, and reportedly one of the most spectacular sunrises in Asia, if you make the expensive ascent to the summit.

On the eastern side of Sabah is the city of Sandakan, and although the city itself offers few attractions it serves well as a base to access the Labuk Bay Proboscis Monkey Sanctuary and the Sepilok Orangutan Rehabilitation Center. From here you can also head north to the Turtle Islands National Park, or continue south to Sipadan Island and arguably some of the best diving around Borneo.

The Proboscis Monkey Sanctuary is a protected scrap of land between palm tree plantations, but it is home to a huge number of monkeys. To reach the feeding platforms you cross duck boards over muddied mangrove roots, where mudskippers waddle and gape maniacally below and hornbills swoop between trees above.

When the food is presented a stirring begins in the distant canopy. A few solitary cries reveal the first of the monkeys high up in the trees. After a few minutes the scene is swarming with monkeys leaping between branches on their descent to the platforms.

Rare natural scene

The alpha males sits proudly in the center of the medley, his pot belly sticking out and radiant red penis on display as females hunch their backs and extend their fabulous noses in a truly bizarre courtship ritual. It's a remarkable show, and as the monkeys disappear back into the jungle you are left with the harrowing knowledge that such spectacles are becoming increasingly rare.

The orangutan center is a well maintained, coach-friendly environment, perfectly catered for the masses of visitors. The introductory video is nauseating in its phony humanizing of the animals; apparently a little love is all they need to survive. Fortunately the narrator casually informs the duly pampered crowd that a baby orangutan is no sweet creature: "Adult orangutans can easily pull a man in two, babies will just take off a limb."

That's better, that's nature. Going out to see the orangutan in droves, you cannot escape the commercialization of the experience. Again feeding platforms are provided, and the teenage orphans swing gracefully between branches to reach the food. One youngster is even walked by the hand through the crowd. It's both remarkable and depressing to see this wonderful animal, a symbol of the wild, behave in this way.

Sadly, the such controlled environments are essential. The Bornean jungle is losing its daily battle against the palm oil plantations. Twenty-five years ago jungle covered over 75 percent of this land, and by the end of this decade it is expected to be under a third.

With that comes a devastating decrease in biodiversity. Palm oil is incredibly valuable, and has helped the Malaysian (and Indonesian) economy and people surge over the past few decades, however, at a considerable price to the islands' wildlife.

Conrad ("Heart of Darkness") went on to describe the "mysterious life of the wilderness that stirs in the forest, in the jungles, in the hearts of wild men." - Will the mystery for the next generation be how we lacked the courage and compassion to save the mystery of the wild?

Liam Singleton is a Shanghai-based freelancer.