Bats are the only mammals capable of true flight. A bat's wing is constructed very much like the human hand, with extremely elongated fingers and membranes stretched between. Bats can be found almost anywhere in the world except for areas with extreme temperatures such as polar regions and deserts. In fact, there are almost 1,000 species of bats worldwide, ranging in size from less than an inch to almost six feet. Many species of bats are considered endangered.