How Do Dolphins Sleep?
When a dolphin needs to rest, it enters unihemispheric slow-wave sleep. This means that one hemisphere of its brain shuts down while the other remains alert, with the eye on that side staying open. This enables the dolphin to surface and breathe as needed, as well as look out for danger. Scientists have tested dolphins with continuous echolocation tasks and found that they can remain alert and accurate for at least 15 days due to this mode of sleep.
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Key Facts In This Video
Every known animal sleeps in some way, even microbes. (0:32)
Dolphins shut off one hemisphere of their brain in what's called unihemispheric slow-wave sleep. (1:41)
Some sharks can stop swimming to sleep without suffocating. (3:49)