Bats are not blind.

More Info: The misconception that bats are blind is a common myth.  In fact, bats have excellent eyesight.  Many people may believe that bats are blind because they do not use eyesight to search for food at night but a sensory system called echolocation, which is similar to the sonar used in ships.

How Bats See

Many bat species can see better in the dark than in daylight and see in shades of white, gray, and black, but the fruit bat uses its keen sight to search for food.  There are 173 different fruit bat species that range in size from several inches to more than five feet from wingtip to wingtip.  The fruit bat seeks its diet of flowers, nectar, and fruit through both sight and smell.

How Do Bats Use Ultrasonic Sound?

Bats use ultrasonic sound to navigate and find food in a process called echolocation.  Ultrasonic sound refers to sound waves that are above audible level-generally anything beyond 20,000 Hz.  The bat emits an ultrasonic frequency between 20-100 Hz.  Different bat species utilize three distinct ultrasonic frequencies, short clicks, frequency-swept pulses, and constant frequency pulses.   Among the two main suborders of bats, the Megachiroptera and the Microchiroptera, the Megachiroptera utilizes the tongue clicks whereas the Microchiroptera order utilizes the frequency and constant frequency pulses.

How Does Echolocation Work?

Echolocation is a sensory system in certain animals such as dolphins and bats that uses ultrasonic sound to help to determine the location, size, and distance of an object in space.  Like sonar, the animal emits a high pitched sound , in the case of the bat either from the nose or mouth,  which will then bounce off of any object it is directed at.  The bat will then use its keen sense of hearing to interpret the sound wave to figure out what it is and how big it is. The process is so precise that a bat can distinguish an object as thin as a human hair, which allows it to easily find a food source as small as a mosquito, making the bat quite useful to humans.