The size and shape of the Batu caves indicate that they were formed 60 - 120 million years ago. Rainwater entered the limestone through cracks, faults and bedding planes from the beginning, to dissolve the limestone from inside and forming the cave passages.
The Dark Cave is generally unknown except to scientists and cavers. The Malaysian Nature Society Selangor Branch Cave Group (MNS-SBCG) built a walkway cover in the area where guano dropping from the ceiling was a major problem for visitors and in the mid-1980s they also began taking groups of interested people into the caves by appointment.
Batu Cave limestone hill supports two very distinct ecologies; one is on the surface and the other in the cave below. The most distinctive feature is its plants. Many species of plants grow here because of the relative isolation of karst towers. Plants growing here make up an important part of the flora. One of the interesting plant found at the entrance of the Dark Cave is the Monophyllea "single leave plant", so named because the plant consist of just a thick succulent stalk with a single large leaf at the end.
The cave fauna consist of invertebrates and vertebrates. By far the best known animals found here are the bats. Dark Cave supports over 200 different species of animals, most of which are invertebrates that depend heavily on the presence of guano provided by the bats roosting in the caves.
The ecology of the cave is a most intriguing one because it exists in total darkness and yet supports an extremely high density population of animals. Sunlight is the primary source of energy for almost everything alive today, but for obvious reasons very little of this is found in Dark Cave. In order for a sunlight based ecosystem to exist here, there must be some means of transporting the energy inside. The bats play a very important role. They bring energy into the cave in the form of their guano (bat droppings).
