Bats are extremely unusual mammals found all over the world in a variety of colors and sizes. They are the only flighted mammals; while some species can glide, like so-called flying squirrels and opossums, no other animal can fly independently. These shy nocturnal creatures are the subject of myths and legends all over the world, and unfortunately some of these legends have maligned the innocent bat, causing some people to be afraid of the animals.
While some people may call bats flying rodents, the animals are not, in fact, rodents. They have their own biological order, Chiroptera, which is separate from the rodents, found in the order Rodentia. Bats are characterized by their leathery wings, which stretch across their forelimbs and often part of their hind limbs as well, and their much smaller hind legs. Unlike birds, bats are not very steady on the ground, since their hind limbs are so weak. Bats also have teeth and claws which are used in hunting.
The bat is a nocturnal animal, preferring to roost in sheltered areas during the day. At dusk, bats emerge to hunt for food. Contrary to popular beliefs about bats, most bats do not, in fact, live on blood. The bulk of bat species are insectivores, and most of the others eat fruit, seeds, and nuts. A handful of bat species have adapted to eat small mammals or to feed on larger ones. Bats are also not a major reservoir for the rabies virus, although bats with rabies tend to be clumsy, meaning that they come into contact with humans more than other bats.
Like most mammals, bats give birth to live young. Their young may be left in the roost at night or towed along by their parents, depending on the species, and most young bats are independent within a few weeks. When bat populations are healthy, the animals can live to around 20 years of age.
Two distinct qualities of bats have captured the public imagination. The first is the use of echolocation for information about their environment. The second is the tendency of bats to sleep upside down. Bats sleep upside down for several reasons. The first is that it allows them to quickly launch themselves into flight, since they can't take off like birds do. Bats are also sheltered by their sleeping arrangements, as competition and predator species don't generally look under things for living creatures. Finally, bats are biologically adapted to roost upside down, as their rear talons naturally close when the animals hang upside down, with the assistance of gravity.