SumatraInto the Jungle

It has been a punishing night by the time I reach Bukit Lawang at half past seven. My flight from Singapore took off two hours late, leaving little hope for a connection in Kuala Lumpur that was supposed to take just ninety minutes. The tickets were booked separately. A glance at the previous week's departures suggested that the onward flight had a reliable habit of being late too, so I took my chances: either I would just make it, or spend the weekend in Kuala Lumpur.

I make it to Medan. After a taxi ride at remarkable speed, I have barely three hours in a sparsely furnished airport hotel before the driver collects me for the jungle. The next four hours are so bumpy that sleep remains mostly theoretical.

The sun already seems surprisingly high, but the village is still asleep in its golden light. An occasional motorbike rattles through the narrow lanes. A rooster crows. The shops and guesthouses are closed. On the way to the starting point, I encounter a small group of Thomas's leaf monkeys, with jaunty black-and-white mohawks and long grey tails.

There is time for tea and honey pancakes on a terrace overlooking the river and jungle. Apparently orangutans and hornbills sometimes appear here. This morning, that luck is reserved for later.

The lanes are busy now, their cloth shops hung with colour. I follow the river to a suspension bridge, with a fine view back across the village. The jungle begins on the other bank. There is a Christmas tree made from palm leaves, a snake hanging in a tree, freshly tapped rubber trees, and finally the entrance to the national park. The real trek begins: slick stones, thick roots, deep mud and slippery yellow earth.

Our first Sumatran orangutan is an enormous orange figure, with a broad, dark face framed by a long beard and limbs of improbable length. He eats fruit without the slightest concern and moves slowly over our heads. Every movement sends drops of water, twigs and fruit raining down. We learn to stand somewhere else.

For a good half hour I watch him looking down at us, wise and deliberate. Has he also booked a tour to see strange great apes? We watch him watching us. A little farther on, a younger orangutan hangs sideways from a vine by one arm and one leg. Then come a mother and baby, and a Thomas's leaf monkey quietly eating fruit close by.

Lunch arrives in rolled palm leaves: an extravagant helping of nasi goreng with fried egg, cucumber and tomato. Then comes a fruit feast of watermelon, mangosteen, snake fruit, rambutan, banana, passion fruit and orange. Sweating in the humid heat, I eat under the gaze of a pig-tailed macaque. Its repeated yawns and stretches provide the entertainment.

The afternoon takes us up and down steep slopes, across little streams and past bright flowers. One elusive insect is green and red, dotted with white, with a long horn-like projection on its head. There are no more orangutans.

The final approach to camp is amphibious. We change footwear for a series of river crossings, and I discover that my long trousers are not quite the advantage I imagined. My flip-flops, which I dislike already, repeatedly try to escape downstream. I fish them out and carry on. Camp is a collection of bamboo frames covered with plastic tarpaulins, with mosquito nets over the sleeping places.

The river is icy cold. After a dip, tea and pineapple, I doze away the rest of the afternoon on the bank. The first heavy drops wake me. Evening brings dinner, warm tea, card tricks and a jungle version of Jingle Bells. Before long, I am ready for sleep.

In the middle of the night, a small animal lands on my face and runs away in fright. By the time I find a light in the pitch darkness and gather myself, it has vanished. Rat, spider or squirrel: the mystery remains unsolved.

I wake well rested, despite a pillow with all the softness of granite. Breakfast is a four-storey sandwich, with passion fruit and mandarin on the side. Under a clear sky, sunlight plays across the restless river as we put our flip-flops back on and retrace yesterday's crossings.

The water glides over rounded rocks, glittering like jewels. It reminds me of the difficult walk through the Zion Narrows a few months ago. Here, the towering canyon walls are replaced by slightly lower slopes buried in green, and the solitude of the American West by a deafening chorus of chirping, twittering and jungle song.

Sumatra may be one of the jungliest places I have ever been. Of all the forests I have walked through, none has had quite so many vines, or such dramatic green slopes cut through by rushing rivers. The closest comparison I can think of is the forest I saw in Brunei a few weeks earlier.

Animals are scarce today, apart from enormous ants, rivers of termites and assorted bloodsucking arthropods. The trail is demanding, but never dull. There are flowers, changing vegetation and that constant soundscape. On the steep climbs I pull myself up by vines; on the descents I use them to swing down with considerable pleasure.

After three or four climbs and descents, lunch is served on a ridge: more nasi goreng in palm leaves, with dragon fruit and papaya joining the fruit selection. In the afternoon I see only a glimpse or two of Thomas's leaf monkeys and plenty of discarded wild durian husks. At camp, a monitor lizard disappears into the undergrowth.

After a good day's walking, I settle beside a river that is flowing with surprising force. Tea and biscuits arrive. While the tea is too hot to drink, I approach a group of long-tailed macaques playing farther along the bank. I photograph their quick leaps and busy social lives. When I turn back, they are already raiding the biscuit plate.

I scramble over the stones to defend it, waving and calling. The macaques are entirely unimpressed. In less than a minute the biscuits are gone, so I abandon the defence and take more photographs instead. Only crumbs remain as evidence that biscuits once existed. The tea tray moves up to the bamboo shelters, where a fresh supply of biscuits arrives and the tea has finally reached a drinkable temperature.

I go back down for a swim. As I step carefully into the cold water, first sand and then small stones wash over my feet. Keeping my footing becomes difficult. Once I let my whole body into the water, the current suddenly has the better leverage and pulls me into the fastest flow.

I reach for a root, a rock, then another rock. Everything is too slippery to hold against the water. For a moment I think this is it. Not the dogs, the mountains, the traffic or the wild monkeys. The water.

Back on the bank, I find a millipede the size of a carrot on a rock, with unsettlingly spider-like legs. I watch until it disappears, then spend the last few minutes of daylight on the same rock.

The biscuit thieves stay around camp, making further attempts on the food and rubbish. Some cucumber, tomatoes, ginger and coffee still disappear. Dinner is even better than the night before; I eat three helpings. Afterwards there is ginger tea and a game of Cheese Thief. Without dice, we make numbered slips from napkins and draw them instead.

After dark, the monkeys retreat into the trees. The gentle drumming of tropical rain lulls me to sleep.

Rain drums on the roof all night. A hornbill's call wakes me after an excellent sleep on a pillow that, this time, is actually soft. Breakfast is instant noodles and another colourful spread of fruit, watched enviously by macaques peering through the trees.

Outside the kitchen shelter, I have to jump aside. Spiked durian husks come hurtling down like sea urchins. Thud. Thud. THUD. The macaques hurry over to collect the scraps. From cover, I look up: high in the old durian tree, perhaps forty metres above, an orangutan is having breakfast.

I brush my teeth while dodging durian husks. As the orangutan climbs down the trunk, the bombardment stops. At the river, the guides lash four inner tubes together, wrap our backpacks in plastic bags and line the raft with sleeping mats. The macaques watch. Behind us, the orangutan swings through the bamboo shelters that were our camp.

We sit deep in the tubes of a raft that does not inspire much confidence. A guide pushes off with a long pole, and the current immediately takes us downstream. He uses the pole to fend us away from obstacles rather than propel us. It bends alarmingly. I am reminded less of a Venetian gondola than of a punt on the Neckar in a particularly rain-soaked Tübingen summer.

With seven people aboard, our four tubes barely stay above the surface. At the bigger drops it feels as though we disappear under the water altogether. We are soaked from head to foot. Against the warm air, the river feels icy, but racing through the current is still enormous fun. My first rafting trip: who would have thought it would happen in the jungle of Sumatra?