In North America, bats fall into mainly predictable categories: they are nocturnal, eat insects, and are rather small. But winging through their lush, green-black world, tropical bats are more numerous and have more exotic habits than do temperate species. Some of them feed on nectar that bat-pollinated trees have evolved to profit from their visits. Carnivorous bats like nothing better than a local frog, lizard, fish, or bird, which they pluck from the foliage or a moonlit pond. Of course, some bats are vampires and dine on blood. In the movies, vampires are rather showy, theatrical types, but vampire bats rely on stealth and small, pinprick incisions made by razory, triangular front teeth. Sleeping livestock are their usual victims, and they take care not to wake them. First, they make the classic incisions shaped like quotation marks; then, with saliva full of anticoagulants so that the victim's blood will flow nicely, they quietly lap their fill. Because this anticoagulant is not toxic to humans, vampire bats may one day play an important role in the treatment of heart patients—that is, if we can just get over our phobia about them. Having studied them intimately, I now know that bats are sweet-tempered, useful, and fascinating creatures. The long-standing fear that many people have about bats tells us, less about bats than about human fear.

Things that live by night live outside the realm of "normal" time. Chauvinistic about our human need to wake by day and sleep by night, we come to associate night dwellers with people up to no good, people who have the jump on the rest of us and are defying nature, defying their circadian rhythms. Also, night is when we dream, and so we picture the bats moving through a dreamtime, in which reality is warped. After all, we do not see very well at night; we do not need to. But that makes us nearly defenseless after dark. Although we are accustomed to mastering our world by day, in the night we become vulnerable as prey. Thinking of bats as masters of the night threatens the safety we daily take for granted. Though we are at the top of our food chain, if we had to live alone in the rain forest, say, and protect ourselves against roaming predators, we would live partly in terror, as our ancestors did. Our sense of safety depends on predictability, so anything living outside the usual rules we suspect to be an outlaw, a ghoul.