How do dolphins sleep?
Quick Answer
Dolphins sleep with one half of the brain at a time, keeping the other half awake so they can surface to breathe and watch for danger.
The Full Story
Unlike humans, dolphins are conscious breathers: they must decide to rise to the surface and breathe through their blowhole. To rest without drowning, they use unihemispheric slow-wave sleep, in which one brain hemisphere sleeps while the other stays alert. The eye opposite the sleeping hemisphere usually closes, while the other eye stays open, often watching other members of the group. Dolphins may rest motionless near the surface, called logging, or swim slowly beside a companion. Bottlenose dolphins spend roughly a third of each day in this kind of sleep, switching hemispheres over time.
Key Facts
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Suggested video title for this topic:
"Half asleep, half awake — how dolphins rest without drowning"