Together with photographer Frits Meyst, two expedition leaders and twelve volunteers, I am in Rimbang Baling: the remote green heart of the Indonesian island of Sumatra. Our operating base is a simple wooden hut on the Subayang river, where I sleep in a dome tent made out of gaze, set on the veranda. You can shower outside under a cut-off water hose in an improvised cabin of tarpaulin, power is only available between six and ten at p.m. I look at my phone: no service. The next couple of days, we will live a life cut off from the outside world. Every day, two teams set out through the dense rain forest to search cells of two by two kilometres. Biosphere Expeditions together with the World Wide Fund for Nature (WWF) has set up a research expedition, allowing tourists to contribute to the preservation of this critically endangered species through data collection. ‘ This year, we focus on the buffer zone,’ Febri explains. ‘In this vulnerable area along the river, where there is a lot of illegal logging, there is the largest gap in information, so here’s where we need the help most.’ The rain forest is rapidly turning into palm plantations. On the thirteen-day expedition, participants varying from a retired couple from California to a lawyer from Germany, set out daily to set camera traps and register traces of the Sumatran Tigers, their prey, poaching and deforestation. ‘It feels like just a drop in the ocean,’ Martyn says, an entrepreneur from Australia, while we cool down in the bright green river. ‘And yet, endangered species have been saved from these drastically low numbers before. I hope to do my part this way.’ I lean back in the water. Boats with inhabitants of the tiny villages along the river pass by. I wave, and the veiled girls give me a shy smile. Cars, bikes or roads are unknown around here. The Subayang river is Rimbang Baling’s highway, the aorta of the jungle.

Water buffaloes swim in the banks, wild boars run along the side and children from the villages on the river wave happily. I get off on a muddy bank, yellow-white butterflies fly around me by the dozen. Every day, we explore one or more defined areas of four square kilometres. Our main goal: setting up a camera trap in a strategic place. These camera traps give insights on how the tigers are spread out in the reserve. ‘That way, we know which areas should be protected,’ Febri explains. ‘Besides that, we study the prey that lives here, like mouse deer, Bornean bearded pigs and armadillos. We need this information to prevent conflict with the local inhabitants. When there is too little prey left, the tigers turn to their livestock. Or worse: to the plantation labourers.’ With a compass in one hand and a detailed, plasticized map in the other, I try to find a straight route through the dense terrain by using altitudes. When we see something relevant along the way, like a paw print of a tiger of signs of illegal logging, we write down the coordinates.

Sometimes, there is a narrow path, maintained by the labourers of the rubber plantations. More often, there are none. In that case, we slash our way through the spinose rain forest filled with starved bloodsuckers. Nature here is hard, not made for tourists. That is exactly what I like about it. I am amazed by the bright red dragonflies and carnivorous plants, while I hold myself up by grabbing lianas and roots sticking out from the trees. What a mighty feeling to be moving around in the habitat of the Sumatran tiger, but especially to contribute to its survival. ‘This is an exquisite place to set a camera trap,’ Febri says, while he moves around some leaves around a large tree trunk looking out unto a clearing. ‘Animals like to use human-made paths, so we have a good chance of capturing something here.’ I press the camouflaged box with the camera firmly against the trunk, while Febri attaches the buckles and wraps the chain lock firmly around the tree. The infrared camera with detection meter goes off as soon as it detects movement. ‘We use the images to identify the tigers based on their strips,’ Febri says. ‘ A tiger is only counted when we capture it twice. That way, we make an estimate of the population.’ I save the exact location in the GPS tracker, so the camera can be collected by the next team in a couple of weeks. ‘We also register other endangered species here,’ Febri continues, ‘like the clouded leopard, the sun bear, the Asian golden cat and the Malayan tapir.’

Tonight we sleep in the rainforest, so that we can place another camera trap in this remote area. Exhausted we exit the boat to set up camp near a rocky beach along the river. Immediately I take a dive in the river to rinse the brown mud and dried blood off my body. The sandals stay on: two days ago one of the expedition members lost the tip of his toe to a snappy turtle. Towards the evening, the jungle that rises up from the green river, comes to life. Monkeys jump from branch to branch and swallows buzz the water. We are not alone here. Apart from the mini bees that try to enter my ears in droves, one can not find a more idyllic spot.

In the jungle behind us, I look for two apt trees to hang my hammock. We make a fire and grill freshly caught fish with chilli peppers. Febri tells us that the adjacent national park, Tesso Nilo, once had the densest tiger population in Sumatra, but at the last survey in 2013, only one was left. ‘Sumatra has 23 tiger populations, one of which in Rimbang Baling. In the surrounding areas, the numbers are decreasing, here they keep increasing. That is why they changed priorities. Recently, a mother with her two playing cubs was caught on one of the cameras. That’s a good sign,’ says Febri. In the future, we want to work on the connections between the current habitats, allowing for an easier crossing for the tigers. For now, we focus on placing the cameras and educating the locals. We try to offer poachers an alternative and lower the conflicts between villagers and tigers.’

That night, I think about the documentary we were shown during the training days, while I slowly sway back and forth in my hammock on the sound of toads and cicadas. One of the camera traps has captured a tiger. A few days later, she passes again, but she finds the forest around the camera to be in ruins. Her house has been destroyed, but where can she go? Habitats of animals all around the world shrink every day, and if this keeps on going, it won’t be long for the end to come for the Sumatran tiger. It does give hope seeing so many people put their best foot forward in helping the tiger’s survival. And I can’t think of a better way than an expedition like this one. An expedition that doesn’t evolve around spotting a tiger, but protecting its natural habitat. One where you crawl through the mud on hands and feet, plucking bloodsuckers of your belly and swim under waterfalls. One where you fall asleep in a hammock, in a rainforest where no tourist has ever set foot. One that will hopefully make a difference, and one to never forget.