Walk to Deer Cave at Mulu for the evening bat exodus

What the experience is

Gunung Mulu National Park covers 528 square kilometres of mountain and rainforest in northern Sarawak, near the border with Brunei. UNESCO listed it in 2000. Beneath its limestone lies one of the great cave systems of the world. Deer Cave is the most accessible of the large caves, a passage some 120 to 150 metres in diameter. Estimates give two and a half to three and a half million wrinkle-lipped bats roosting in its roof, and on most evenings, weather permitting, they leave to feed.

The walk and the cave

A raised boardwalk runs for about three kilometres from the park headquarters through the forest to the cave. The visit is made with a park guide and usually begins at Lang’s Cave, a smaller chamber of fine stalactites, before entering Deer Cave. The scale takes time to register. The path crosses the floor far below a roof lost in darkness, with the smell and sound of the bat colony overhead.

The exodus

Outside the cave, a viewing area faces the cliff. In the late afternoon and early evening, usually between about five and half past six, the bats begin to emerge, in groups of many thousands. Each group forms a ribbon that twists and coils as it moves away over the forest, a formation thought to protect the bats from the bat hawks that wait for them. The flight lasts perhaps fifteen to thirty minutes. It is not guaranteed: in rain the bats may not come out at all, and on some days they do not emerge.

When to go

The park is open all year, and rain is possible in every month. The drier months, roughly March to September, give the best chance of a clear evening. Allow two evenings in case the first is wet.

Good to know

Mulu has no road access. Flights arrive at its small airport from Miri, Kuching and Kota Kinabalu, and are sometimes delayed by storms. Only about a tenth of the park is open to visitors, and all cave visits are guided and booked through the park. Three days allow for Deer Cave, a boat trip to Clearwater Cave and Wind Cave, and the canopy walkway. The Pinnacles, a field of limestone blades on Mount Api, are a demanding trek for the fit, usually of two to three days.

Why OKYTO recommends it

The bat flight is one of the great wildlife events of Southeast Asia when it happens, and it is seen from a viewing area after an easy walk. The cave before it gives the scale of the place. Travellers interested in the caves of Sarawak can add Niah, reached from the same town of Miri.