T his incredible volume along with the terrain, not too steep and not too flat, allowed the lava to flow at a rate conducive to tube formation. Its surface, in contact with cool air, solidified. Now like a thick, insulated underground river the lava beneath forged a path downstream, the longest arm finally extending 160 kilometres north-west. Hundreds of thousands of years have seen weaker sections of the tube collapse to form today's line of depressions and caves. It is this remarkable lava-cast environment in which bats have triumphed.
T hanks to their sheer numbers, bats have a major influence on life inside and around the caves.
W hen they breed, three major nursery caves, usually open to the public, are closed. District ranger Lana Little describes this as sound management practice that will help ensure young bats can be raised without disturbance. By the end of March the cycle appears to be complete and tourists can safely return to these restricted areas. T he policy recognises how important bats are to the unique biological system that has developed around Undara's tubes. Bat droppings or guano can build thickly on the tube floor, often supporting fields of fluffy white fungi.