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While sleeping, the bottlenose dolphin shuts down only half of its brain, along with the opposite eye. The other half of the brain stays awake at a low level of alertness. This attentive side is used to watch for predators, obstacles and other animals. It also signals when to rise to the surface for a fresh breath of air.

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After approximately two hours, the animal will reverse this process, resting the active side of the brain and awaking the rested half. This pattern is often called cat-napping.