HomeScienceAlways alert, even in dreams: The extraordinary sleep of Dolphins

Always alert, even in dreams: The extraordinary sleep of Dolphins

Dolphins sleep with one half of their brain awake, staying alert while resting. Discover the fascinating science behind this extraordinary ocean survival strategy.

October 16, 2025 / 17:24 IST
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Dolphin's sleep is known as unihemispheric slow-wave sleep (USWS). (Image: Canva)
Dolphin's sleep is known as unihemispheric slow-wave sleep (USWS). (Image: Canva)

Dolphins are intelligent creatures, and they sleep in a very interesting manner. This phenomenon is referred to as unihemispheric slow-wave sleep (USWS). Basically, in this phenomenon, a half of their brain sleeps, and the rest is awake. This enables them to evade danger and remember to come up to breathe air.

Sleeping with One Eye Open

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Contrary to the human beings, who must sleep completely, dolphins sleep half the brain. The awake hemisphere deals with swimming and breathing. While doing so, they do not hit obstacles nor become the prey of the predators. It is like sleeping with half the eyes shut- a clever survival tactic at sea.

Why They Do It