dol­phins shine beams of sound

World of Animals - - Seeing In The Dark -

Dark­ness doesn’t stop a dol­phin from find­ing food. These marine mam­mals sleep spo­rad­i­cally through the day rather than snooze at night, so they need to be able to nav­i­gate the pitch-black wa­ter.

In the ab­sence of light dol­phins emit a series of click sounds into the ocean in front of them. Just like light bounces off an ob­ject and into the eye, the sound waves re­bound off any ob­jects in the wa­ter and back to the dol­phin.

The re­turn­ing clicks aren’t re­ceived by the ear. Dol­phins lost their ex­ter­nal ear flaps over mil­lions of years and only a tiny pin­hole re­mains on each side of the head. In­stead, re­bound­ing sound trav­els along the lower jaw, which is in con­tact with the in­ner ear.

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