How do Dolphins sleep?
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balancing up-side down
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in vertical position
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mouth kept open
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one eye kept open
Dolphins sleep using unihemispheric slow-wave sleep - they rest one brain hemisphere at a time while the other remains awake. This allows them to maintain consciousness for breathing and predator detection. They don't sleep upside down, vertically, or with their mouth open.
Dolphins are conscious breathers, so they can never fully lose consciousness or they'd stop breathing and drown. They solve this with unihemispheric slow-wave sleep: one half of the brain rests while the other stays alert, and correspondingly one eye stays open (the eye opposite the resting hemisphere) to watch for predators and surface for air. The other options — sleeping upside down, in a vertical position, or with mouth open — aren't how dolphins sleep; those describe other animals or are simply inaccurate.