They find their way by sending out high-pitched sounds (at a level too high for humans to hear). The dolphins then listen for the returning echoes as they bounce off objects. This is called "echolocation", and it lets dolphins know what is around them.
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Makes me believe something is messing up the Echo signal being sent back to them. Like Sonar or underwater earthquakes or under water volcanos or something is making them feel so bad they want to beach themselves. I know I got a cold last Thursday that had me beached in the bed all weekend not wanting to live.
Another view is:
•one of the pod got into trouble and was followed by the others
•that they were chasing a shoal of fish and then couldn't get back into deeper water
•or perhaps that they were being chased themselves
As dolphins are known for being a very social species, it's often thought that a distress signal sent out by one, brings others nearby flocking to help. "They're like humans, in that if your house and family were under threat, you'd go and help them, rather than run the other way," says Ms Dolman.
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I also found this
Since they are mammals, the dolphins have ears that are sensitive to large changes in pressure underwater, he said.
"If their eardrums are damaged they become disorientated and they float up to the surface," Mr Sarmiento said.
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