blind as a bat

[K99]

Why do people say 'blind as a bat' Are bats blind?

[ham]

no bats arent blind but it could be that they only fly ant night and use sound to find there way round, so they could be classed as blind i suppose because the cant see in the dark and thats the only time the come out!

[Tha-Flash]

I thought they were blind, many people say they are but they use something like "Sonic boom" hearing to tell where they are going.

[New Forester]

No, bats are not blind. However, the smaller sort (Microchiroptera) do have very small eyes. They do use them, but can manage without. These are the ones which use echolocation ("sonar", not "sonic boom", Thai-Flash!). They often fly in the proper dark -- even good eyes need some light, but sound does not. The larger kind of bats are Macrochiroptera, often called fruit bats or flying foxes (though many of the micros also eat fruit, and some are quite big). Macros have large eyes and use them to fly with, keeping to dawn, dusk or moonlight -- or daylight. They do not echolocate properly, though a few kinds do it a bit with clicks.