MIRI: As the sun sets behind the Bornean rainforest, the sky above Mulu National Park transforms into a spectacular natural stage as thousands of bats stream out of the mouth of Deer Cave.
The cave’s inhabitants form swirling black waves in the evening sky in a phenomenon known as the bat exodus, which takes place almost every evening.
For nature lovers and adventure seekers, it is not just a sight to behold but an extraordinary experience – like watching a perfectly-orchestrated symphony of nature.
Mulu National Park was recognised as a Unesco World Heritage Site in 2000 for its geological features and rich biodiversity.
Deer Cave, one of the caves located there, is said to be among the largest limestone caves in the world and is home to millions of bats.
To reach the bat exodus viewing area, visitors would take about 45 minutes traversing along a three-kilometre plank walk crossing peat swamp, streams and limestone outcrops before arriving at an open area near the cave entrance.
A group of social media influencers, along with Bernama, had the chance to witness the phenomenon during a familiarisation trip to Mulu National Park organised recently by the Sarawak Tourism Board in collaboration with Gaya Travel Media.
According to Mulu National Park guide Richie Philip, 35, the cave is home to an estimated two to three million bats from 12 species, with the Wrinkled-lipped bat colony being the most dominant, creating striking formations as they leave the cave.
“They usually come out between 5pm and 6pm. Sometimes they don’t emerge if it rains heavily. But when conditions are right, the bats pour out in an unbroken stream, swirling through the sky... It is truly an incredible sight,” he told Bernama.
Richie explained that before their mass exit, the bats circle the cave entrance in spiral or S-shaped formations as a natural strategy to confuse predators such as eagles that often patrol the area.
The bat exodus occurs only at Deer Cave as its main chamber, which rises more than 100 metres high, is partly illuminated by sunlight and unobstructed by surrounding trees.
“The bats circle inside the chamber before flying out, waiting for other groups to join them so they feel safer. At the same time, this formation also confuses the eagles outside, making it harder for predators to catch them,” he said.
The bat stream can last several minutes, forming what looks like black clouds across the sky, with the bats flying at speeds of up to 70kph for as far as 50km before returning to their habitat the next morning.
Richie added that the bats are not only a major tourist attraction but also vital to the cave’s ecosystem, as their guano provides food for numerous insect species and fish.
“Without the bats, the cave’s food chain would collapse,” he said.
Richie also advised visitors to remain silent when watching the phenomenon, as noise can cause the bats to fly higher, whereas in silence, they fly lower, allowing the sound of their wings flapping – like the gentle patter of applause – to be heard clearly.
