Manta rays are continuously swimming throughout their life span. But how can they sleep while they’re swimming? Or do they technically not sleep at all?
Note: I have also recorded a video about this topic. If you would prefer to look & listen, click play to watch the video. If you prefer reading, read on below!
Why Manta Rays Can’t Stop Swimming…
Born into a life of perpetual motion, manta rays must keep swimming to survive. They must remain in a constant state of moving forward in order to keep oxygenated water passing over their gills. This is what keeps the mantas alive; if a manta stops swimming, it would suffocate, die, and sink to the bottom of the ocean.
… And Why That Means They Can’t Sleep
The human body requires periods of sleep in order to restore, rejuvenate, and reset the brain. We lay down and rest.
On the contrary manta rays are always moving and although it’s never been experimentally demonstrated it’s assumed that their brain never fully switches off. They are moving forward and hold a conscious state of mind through the entirety of their lives of 40-80 years.
It’s hard to imagine but many sharks and other rays are destined to do exactly the same.
Fun Fact: How Dolphins Sleep
This often prompts a question about dolphins and their ability to turn off half of their brain.
Although dolphins live in the ocean among the manta rays, they are mammals and not fish. They are warm-blooded, have no gills, and breathe through their blowhole.
Dolphins are able to shut down half of their brain, leaving one brain hemisphere resting while the other is awake and alert. This implies that the dolphin can still watch out for nearby predators, while also making the conscious decision to breathe by regularly returning to the surface.
To answer the initial question, manta rays don’t sleep. As far as we know, or even perhaps manta rays simply cannot sleep. It’s definitely classed as a long amount of time that mantas live and swim, and there’s always some kind of gliding or swimming motion taking place.