In the dark, at 3:30 a.m., we have to remind ourselves this is Borneo. The island’s tropical vibrancy is absent in our flashlight beams; we are tramping through a colorless ghostscape of gnarled shrubs and dancing shadows. The heavy pungency of the rainforest has dissipated, and the humid heat of the lowlands is a vague memory from the previous day. The air is thin and searingly cold.

The path twists and turns in one relentless direction: up. Every weary step takes us higher. The effort leaves us breathless, and the temptation to stop is hard to resist. But we must resist. The earth is turning, and dawn is approaching from the east. We need to reach our goal before first light.

After what seems like an age of walking, the terrain changes. We break out of scrubland onto bare granite. In places the slope is so steep we must drag ourselves upward using ropes fixed to the rock face. At last the ground flattens, and we arrive. We are not alone.

At least two dozen people have endured the same trek this morning. As the horizon brightens, we jostle for position at 13,435 feet above sea level. We are standing on Low’s Peak at the summit of Mount Kinabalu, one of the tallest mountains in southeast Asia. As the sun rises, we ready our cameras and begin to click. This is the moment that makes the early start and punishing hike worthwhile.

The gaudy beauty of daybreak is not the only reason we are here at this ridiculous time of day. As the heat mounts at lower altitudes, the cloud cover will increase. Within an hour or two, the view will be completely obscured. This is our only chance to enjoy it.

And what a view. To the west, the mountain tumbles down toward the South China Sea. The city of Kota Kinabalu nestles beneath us between the highlands and the water. To the east, the land stretches to the Sulu Sea, which is concealed by morning haze. North of us is the very tip of Borneo. And to the south lies the vast, green hinterland of the world’s third-largest island.

The name “Borneo” traditionally conjures images of impenetrable rainforest, exotic wildlife and fierce tribes of cannibalistic headhunters. Even now, in the 21st century, there is some truth to those preconceptions.

Admittedly, logging has frayed the rainforest; many of the exotic species are threatened with extinction, and most of the local tribes have been “modernized.” Yet there are still swathes of untamed forest, and during recent skirmishes between the indigenous Dayak people and Indonesian settlers there have been documented reports of beheading and cannibalism.

Despite resistance from the native tribes — there are more than 200 ethnic groups here — the modern world has brusquely stamped its mark on Borneo. The island is shared by three countries. In the north are two states of Malaysia — Sabah and Sarawak. Two small enclaves on the northwest coast, the final remnants of a great Asian empire, make up the independent sultanate of Brunei. The bulk of the central and southern part of the island is known as Kalimantan and belongs to Indonesia.

I have come to Sabah, the most developed — and, for a visitor, the most comfortable — corner of Borneo. My trip began and will end in a 5-star beach resort. In between, I am searching for the Borneo of my wildest imagination.

Here on the summit of Mount Kinabalu I am dressed in layers to fend off the morning chill. For the first few days of my visit I had sweltered on a succession of sandy beaches, periodically cooling myself by snorkeling over the surrounding coral reefs.

From my hotel close to Kota Kinabalu, I had easy access to the five offshore islands protected within Tunku Abdul Rahman National Park. Each morning I headed out in the hotel’s speedboat. The inevitable presence of other tourists slightly dulled the desert island idyll, but once in the water or on the trails into the interior, I was able to leave behind all trace of other humans and could play the part of a castaway.

Around Mamutik Island, the coral reefs teemed with marine life. I swam among glittering shoals and, on one thrilling excursion into the water, floated above a banded sea snake, one of the world’s most venomous creatures (their venom is 10 times more potent than that of a cobra, though, thankfully, bites are rare).

On Sapi Island I mostly confined myself to shade due to sunburn from the previous day’s snorkeling and spent some time getting my first taste of the Bornean rainforest, encountering monitor lizards and macaque monkeys.

That was merely a prelude. The following day I crossed mainland Sabah to Danum Valley Conservation Area, a wonderfully preserved expanse of pristine rainforest. The abundance of life within the forest comes with a downside. On each jungle walk I picked up a remarkable variety of insect bites, and on one occasion a tiger leech latched on to my ankle. My luxurious cabin at Borneo Rainforest Lodge was a welcome cocoon from these discomforts.

Borneo is one of the most bio-diverse places on Earth, with an incredible array of endemic plant and animal species. For casual enthusiasts, the star attractions are the big mammals.

Locally, none are bigger than the Bornean elephant. The island’s unique subspecies is actually a pygmy variety of the Asian elephant, but you wouldn’t believe it when face-to-face with one on the jungle trail. Fortunately, they are extremely docile and can sometimes be approached to within a few feet. More often, as in my case, all you get to see of the camera-shy pachyderms is a wrinkled grey rump disappearing into the foliage.

The highlight of my stay was a view of a wild orangutan. He sat hunched high above us on a branch that appeared insufficient to take his weight. When he decided that he’d had enough of our attention, he unfurled his lanky arms and swung to thicker cover with surprising agility and grace.

Another local primate, the bizarre proboscis monkey, can be seen at Tabin Wildlife Reserve, a two-hour drive east of Danum. I visited with a group of elderly Australian women. When we found a proboscis monkey sitting in a tree, one of them observed the huge, bulbous nose and protruding pot-belly and chuckled, “Reminds me of my husband.”

“Looks like he’s pleased to see you, Jenny,” one of her companions said, drawing attention to another prominent feature of the monkey’s anatomy. Male proboscises tend to be in a near-permanent state of arousal.

“On second thought, that’s not like my husband at all.” All of the women dissolved in helpless laughter. The proboscis monkey looked in our direction disdainfully, then turned his back.

The environmental threats to this island cannot be shrugged off by the wildlife quite so easily. Deforestation for timber — and, lately, to make way for biofuel plantations — has had a severe impact on natural habitats. According to the World Wildlife Fund, Borneo’s forest cover is being reduced by an area roughly the size of Massachusetts every year.

From the top of Mount Kinabalu, the impact of humans is clear to see in every direction. Roads wend between oil palm, cocoa and rubber plantations. Many of the last remaining pockets of virgin rainforest are under threat.

The granite summit of Mount Kinabalu is an immovable, unchanging object. The mountain’s lower slopes, protected as a national park, remain cloaked in primeval forest. As the wilds of Borneo continue to be whittled away, here at least there is permanent refuge.

Trudging through the dappled forest shadows at the start of my ascent the previous morning, my expectations of this brooding island had been met. Every sound, every sight, every scent drew me deeper into the heart of Borneo.

Info to Go

The Shangri-La Tanjung Aru Resort and Spa near Kota Kinabalu is Borneo’s premier beach hotel. The Borneo Rainforest Lodge offers rainforest excursions without compromising on comfort. For information, visit www.borneotourism.com.