Orcas spend their entire lives at sea. It’s where they’re born, where they feed, where they have families, and where they die. And yes, it’s even where they sleep!
For us humans, sleep is a time when we’re unaware of what’s happening around us. In other words, we’re unprotected and totally at the mercy of our surroundings. But for killer whales and other cetaceans, entering this “unconscious” state isn’t a possibility. If they did, they would drown!
So the big question is: How do killer whales sleep without dying?
The science of orca sleep is quite complicated and is always being studied. But we do know quite a bit about how these giant creatures get their sleep!
Killer whales are voluntary breathers
Unlike humans, who breathe without thinking about it, killer whales must consciously remember to breathe—even in their sleep! That means their brain has to remain partially active while they snooze.
Killer whales can shut down one hemisphere of their brain at a time
Dolphins and beluga whales sleep by shutting down one hemisphere of their brain at a time. Because killer whales are physiologically similar to these species, it’s thought that they sleep in the same way.
While half of the killer whale’s brain catches up on sleep, the other half controls the breathing. What’s more, one eye remains open (on the “awake” side of the brain”) while the other stays closed.
This is called unihemispheric sleep, and it’s a trait that many species share, including pilot whales, porpoises, Stellar sea lions and even chickens. Yes, chickens!
Killer whale calves don’t sleep for the first few weeks of their lives
For the first month or so of their lives, killer whales calves are constantly on the move. All that activity helps regulate their body temperature (their blubbery insulation isn’t fully developed yet), keeps them afloat, and keeps them safe from predators.
But calves can’t just swim around on their own—they need their mother by their side 24/7. A young whale and its mother swim close together in what is known as an “echelon formation,” where the calf eats, rests and sleeps while being towed along in her mother’s slipstream. While a convenient setup for the calf, it means no sleep for momma—for a month.
Killer whales sleep in pods
While resting, killer whales swim close to other members of their pod. This formation can last for hours and is quite an exhilarating sight to see!
Eagle Wing Tours was lucky enough to spot L Pod resting near Victoria BC, and even caught it on video!