Bats are the only mammal that can fly. They have a furry body, and their wings are covered by a smooth, flexible skin. Bats mostly live in attics, caves, trees or other sheltered places. They come out only at night, and when they rest during the day, they hang upside down. Bats live all throughout the world, except for Antarctica and the Arctic. Most bats are harmless to people, but be careful not to touch them because they do have rabies. Bats actually help humans by eating annoying insects.