Katherine Gorge is a home to 500,000 bats. They take off after sunset and disperse in the search for food, and come back around 5am in the morning. My knowlege of time of their return is first-hand - it is impossible to sleep through their screeching in the morning. I also made a mistake of setting up the tent in the shade of a tree; I don't know if the whole half-a-million bats were shitting on my tent, but the damage they caused was quite impressive. Katherine Gorge, Northern Territory, Australia