Numbering between 1,000 and 2,000 species, bats range in size from less than 1 in. The body is furry and mouselike, with the forelimbs and extensions of the skin of the back and belly modified to form wings. Bats are most abundant in the tropics, and temperate species often hibernate or migrate to warmer areas in the winter. Most bats see well but depend on echolocation to navigate in the dark. Vampire bats regurgitate blood for bats that can't find food.
Bats can hear insects' footsteps.
Austin, Texas, is home to the largest urban bat colony in North America. At last count, an estimated 1.5 million Mexican free-tailed bats were living in the vicinity. When bats emerge from a cave, they fly in a left-spiraling pattern to keep from bumping into each other. The world's smallest mammal is the bumble bee bat of Thailand, weighing less than a penny. The pallid bat of western North America is immune to the stings of scorpions and even the seven-inch centipedes upon which it feeds.