However, in ecological terms, the diversity of tropical bats is even greater, because they have such diverse feeding habits. The forty U.S. species are all aerial insectivores, which means they catch flying insects in the air. All Neotropical bats have echolocation systems to help them navigate in the dark, in the forest understory, and in caves. They emit pulses of clicks through their nose or mouth, and then sense the returning sound, which tells them about their environment. Most echolocation sounds are ultrasonic, and beyond the range of human hearing, but some people can hear in the lower part of that range, and can hear bats as they fly by.
Bats also have good eyesight, especially in low light.
These sensory abilities mean that bats are not likely to run into you, even when they fly close by. But like many animals, a bat will bite in its own defense if it is restrained in the hand. Insectivorous bats have a highly-developed echolocation system which allows them to catch insects on the wing. Because bats are such important predators, any adaptations by the insects which allow them to avoid being eaten will be strongly favored and will be selected for in the insect populations. One group of night-flying moths has evolved a highly specialized mechanism in response to bat predation.