The music in the background is the traditional malaysia lute, called a gambar. After the gambar Panjabi MC plays. This video was taken right before sunset. During this time Malaysia was suffering from heavy flooding. The bats were going to eat off the tops of the tree as they do every night. They live in a cave called Deer Cave -- named after the deer that once lived there. There are also glowworms inside the cave that leave glow-in-the-dark goo on you if you touch them.
Click this video thumbnail to watch a big version of the daily bat exodus. There are literarlly 5,000,000 bats. That's right 5,000,000!
All little background on Malaysia:
Malaysia is a Muslim nation although it is a mix of at least three cultures: Malay, Indian, Chinese. The official languages are Bahasa Melayu and English. The flag, pictured to the right here, is strangely somewhat similar to the USA -- a country it has virtually nothing in common with.
A bit about Gunung Mulu National Park:
Gunung Mulu National park, a UNESCO heritage site, is the largest national park in Malaysian Borneo. It's famous for its enormous cave network and variety of animal, insect, and plant life. It's difficult to get to and most people choose to fly on a small puddle jumper to arrive in Miri the closest city -- which is nothing more than a small town. You can arrive via winding rivers, but that is a long, arduous journey.
The National Park is mainly primary rainforest and, because it gets so much rain, the forest floor is very swampy. There is an extensive network of boardwalks and cement trails around the headquarters that connect the hostel with the various caves and points of interest (like a small area flourishing with pitcher plants), so day trekking does not require too much in terms of special gear or repellent. As one guide of the park says while sporting a big smile, "You're usually safe from the leeches!" Flying into the the park is and affords incredible views of the limestone mountains (and of the Pinnacles) and of the vast expanse of jungle that the park encompasses. Mulu's biggest attractions lie beneath the forest floor. Over two hundred kilometers of cave passages have been discovered so far and this figure is thought to represent only 30% of that which actually exists.
The above video shows bats flying out of part of that vast network.