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Have you ever heard the expression ‘blind as a bat’? It is far from true as almost all bats have reasonable eyesight. Have you ever been in a bat cave, or watched a documentary about bats and wondered how they could see in those pitch black caves?
It was once thought that the bat relied mainly on its eyesight to see in the dark. One scientist though, by the name of Lazzaro Spallanzani discovered that a blinded bat could fly and capture prey, and a bat with earplugs couldn’t. Later on, G.W.Pierce developed a sound detector that proved that bats do use sound to get around in the dark.
But how do they use sound to get around? Well just as we rely on the sun for light to see, bats rely on sound waves to know where it is going. To see in the dark, bats produce sound pulses. The pulses made from the bat spread out like the light from a torch. When the pulse comes in contact with an object, then an echo bounces back to the bat. The bat uses high pitched sounds that most creatures can’t hear. This means that the bat can catch its prey without being seen or heard. Even its predators find it hard to catch them. A bat’s call may last from 1 to 100 thousandths of a second. Using calls of different pitches means the bat recognizes the order of which the echoes return. This means that the bat builds a mental picture of the surroundings in the bat’s mind. The bat then listens for changes, like an insect moving around.
Individual bats have their own call to tell each other apart. By the bat keeping its call short the bat avoids confusion, so they don’t receive a calling from another bat when they are giving the call. The bat can change volume and the quality of its sounds to suit the surroundings it is flying through. When a bat is flying close to trees, the bat uses a lower volume. If a bat is flying from one place to another, for instance from one tree to another tree it will use simple calls, but when hunting the calls increase in volume and quality. Although a bat's high pitched calls are too high for humans to hear, some people can sense the sound.
The fruit eating bat has a good sense of sight. Several species of insects can hear a bats call and take action. Some moths that can hear a bat's call can send their own call to confuse their attacker.
The wave length of a bats call is probably between 10 to 100 khz, which is beyond human hearing. Echoes sent from the bat to prey and sent back are formed into a picture in the bats brain showing an accurate picture of where the prey is and the size of the prey. So if you see a bat on a documentary or in a bat cave, think about how marvelous it is and how good its hearing is.
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