Cát Tiên National Park

Stand still for a moment and listen. The forest here is never silent. There is the dry tick of insects in the leaf litter, a sudden flap of wings somewhere above the canopy, and the slow drip of water from broad green leaves. The air is thick and warm, and it smells of wet earth, crushed bark and something faintly sweet. You have crossed a river to reach this place, and on this side of the water the forest takes over.

This is Cát Tiên National Park, one of the largest areas of lowland tropical forest left in southern Vietnam. It covers roughly seven hundred square kilometres, spread across the borderlands of several provinces. The park was created in 1992, when separate protected areas were joined together into one national park. Most visitors know only a small corner of it — the area around the headquarters, the river crossing and the trails that start from there.

The river you crossed is the Đồng Nai. It forms much of the park's boundary, and it gives the whole region its name. For generations it has carried water, silt and traffic down toward Ho Chi Minh City and the sea. Here, though, it feels wide, brown and unhurried. The short boat crossing is a useful moment. It marks the line between farmland and forest, between the noise of motorbikes and the noise of birds.

The forest itself is a patchwork. Some of it is tall, old lowland forest, with trees that rise far above the trail. Other parts are dense with bamboo, grassland or open woodland. That mix is partly natural and partly a result of history. During the Vietnam War, parts of this area were sprayed with chemical defoliants and damaged by fighting. In many places bamboo grew back first, and it still dominates large stretches today.

Here is something most visitors do not realise. Cát Tiên was the last place in Vietnam where the Javan rhinoceros survived. This was a separate, tiny population, found in a remote sector of the park and confirmed by researchers in the late twentieth century. Conservationists tried to protect the last few animals. But in 2010 the body of a rhino was found with its horn removed, and soon afterwards scientists concluded the species was gone from the country.

That loss shapes the way people talk about Cát Tiên today. The park is not only a place to see wildlife. It is also a reminder of how quickly a species can disappear, even inside a protected area. Rangers, researchers and rescue centres now work here on the animals that remain — gibbons, primates, bears, crocodiles, and a long list of birds. Many of their stories are still unfinished.

If you arrive early in the morning, you may hear the park's most famous sound. It is a rising, bubbling call that travels a long way through the trees. These are gibbons, small apes that live high in the canopy and sing to mark their territory. The species here is often called the yellow-cheeked gibbon, because the females are golden-coloured and the males are black with pale cheeks. Seeing them is difficult. Hearing them is far more likely.

On an island in the Đồng Nai River, close to the park headquarters, there is a rescue and rehabilitation centre for endangered primates. It cares for gibbons, langurs and lorises that have been taken from the illegal wildlife trade. Some animals are prepared for release back into the forest. Visits to the island are usually arranged in advance with the centre, and they give a rare chance to see these animals up close while learning why they were rescued.

Deeper in the park lies Bàu Sấu, which means Crocodile Lake. It is a seasonal wetland surrounded by forest, and the wetlands around it are recognised as internationally important under the Ramsar Convention, a global treaty that protects key wetlands. Siamese crocodiles, which had almost vanished from Vietnam, were reintroduced here. The walk to the lake takes time, and in the wet season the trail can be muddy and full of leeches. Many people say the quiet at the water's edge is worth the effort.

Cát Tiên is also a place for birds. Hornbills, pheasants, peacock-pheasants, kingfishers and many smaller forest species live here, and birdwatchers come from many countries. You do not need to be an expert to enjoy them. Watch for flashes of colour in the understorey, and listen for heavy wingbeats overhead — a hornbill in flight makes a sound like a slow, rough whoosh. Dawn and late afternoon are the busiest times for birdlife.

As evening falls, the forest changes again. The insect noise rises, frogs start calling from wet ground, and the light turns orange through the trees. Guided night drives with a spotlight are often offered from the headquarters area. On these trips, people look for the reflected eyes of deer, civets and other night animals in the grass. Nothing is guaranteed. The forest does not perform on schedule, and that is part of its honesty.

The trees themselves are worth your attention. Along some trails you will find giant trees with enormous buttress roots — wide, thin walls of wood that spread out from the trunk like the fins of a rocket. They help support tall trees in shallow tropical soil. Strangler figs wrap around other trunks, slowly replacing them. Put your hand on the bark and you can feel the difference between species: smooth and cool, rough and flaking, or covered in moss.

The wider region is also recognised as part of a UNESCO Biosphere Reserve. This is a designation for areas where conservation and human communities are meant to exist side by side. Outside the park, villages farm, fish and trade along the river, and some families run small guesthouses for visitors. The forest and the people around it are connected. What happens to one, sooner or later, affects the other.

Before you leave, pause on the riverbank or at the edge of a trail. Look at how many shades of green surround you, and how little open sky there is. Listen again for the birds and the insects. Somewhere out there, a gibbon family is moving through the canopy, and a crocodile is resting in the shallows. When you cross the river again, notice the moment the forest sound fades behind you.