Bat Conservation International (BCI)- There are more than 950 species of the mammals worldwide, and they're pretty independent thinkers. But yes, they do spend at least some hours each day roosting upside down, and yes, they do poop. But their secret is, they don't do those two things at the same time. Bats sometimes go to the bathroom on the wing, so that's no problem. When they're snoozing in their roosts-- a cave, a tree, an attic and nature calls, they flip themselves right-side up, fire away, then flip back again. Most bats have a "thumb" along the top edge of their wings that can grip a roost as well as their feet can. And if you think pooping is tough, consider giving birth upside down. Many bats do that too. Guano is also a very valuable fertilizer.