4. Orcas Are Never Fully Asleep
Orcas, like many other ocean-dwelling mammals, are manual breathers. Unlike humans, who have a subconscious reflex that keeps us breathing even in deep sleep, killer whales must choose when they breathe. That means that they can’t go completely unconscious like us or they would sink and die!
Instead, orcas practice something called “unihemispheric sleep,” where one half of the brain shuts down and the other stays alert. This lets the killer whales keep an eye out for danger and continue to breathe while still getting the rest they need. They switch which side of the brain is “turned off” to ensure that they’re getting enough rest! And while they’re not fully conscious, they’re still capable of travel; orcas that are sleeping will swim slowly and steadily, close to the surface of the water, so that they can easily breach whenever necessary.