Ever wonder how bats navigate so well during the night and even in the darkest of caves? Bats don't have very good eyesight, instead they generate very high sounds and then listen for the echoes. The echoes provide information on what is ahead - thus they "see" using sound instead of light. This amazing feature is called "sonar". Sonar is also used by the porpoise and by submarines.
In a bat–swarm, in cave or night air, a bat can know its own sound among thousands of mobile neighbours, detecting its own signals even if they are 2000 times fainter than background noises. It can “see” prey, such as a fruitfly, up to 100 feet away by echo location and catch four or five in a second. And this whole auditory system weighs a fraction of a gram! Ounce for ounce, watt for watt, it is millions of times more efficient and more sensitive than the radars and sonars contrived by man. The bat “sees” with sound better than light.