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Like dolphins, killer whales are voluntary breathers, meaning their breathing is not automatic like it is for humans.
Instead, they must consciously rise to the surface and breathe. This makes sleeping for them much different than it is for other animals.
Studies on dolphins and beluga whales have shown that they sleep by shutting down only one hemisphere of the brain at a time, thereby allowing them to both rest and have control over their breathing. It is thought that killer whales, being closely related to dolphins, do the same thing.
Studies indicate that during a killer whale's first few months of life, neither the calf nor the mother sleeps at all. Once the calf becomes an adult and can fully breathe by it's own, it’s when they get their good night sleep.
