Bat is a truly great creature. It has all the characteristics of mammals while also possessing the skill of a bird in flight. There are more than 800 species of bats in the world. They are of different sizes, shapes, and lifestyles. They live all over the world. Bats also have an unique feature. It is the only mammal that can truly fly. The upper arm of the bat is short while the forearm is very long. The wrist is very small and from it comes the thumb and the four longer fingers. The thumb is short and used for climbing or walking. The fingers are long and thin, interlocking the fingers in the wing. This arrangement of having the fingers in the wing gives the bat amazing flight maneuverability. Bats produce ultrasonic sound and then use the echo of the returning sound to sense the world around them and in particularly to catch insects. These sounds are usually out of the humans’ range of hearing. This system is similar to that of dolphins. The sound is in the form of clicks that increase as the bat gets closer to the insect or whatever it is tracking.