How Dolphins Sleep Without Drowning (and Why They Might Not Dream) | Smartest Year Ever (June 18, 2025)

 It’s Weird Animals Week on Smartest Year Ever, and today, Gordy dives into one of the ocean’s strangest adaptations: how dolphins sleep without drowning—and what that reveals about their brain structure, breathing, and even the limits of REM sleep.

Dolphins are mammals, just like us. But unlike us, they can’t go fully offline—because every breath they take is voluntary. So how do they survive without sleep paralysis dragging them under?

This episode explores:

• Unihemispheric slow-wave sleep (USWS)
  

• Dolphin brain hemisphere independence
  

• Real EEG studies on split-brain sleeping
  

• Whether dolphins can dream
  

• Evolutionary comparisons to whales, birds, and even humans
  

And if you’ve ever slept poorly in a new hotel bed, your brain might’ve done something weirdly dolphin-like too…

Sources:

• Lyamin, O. I., et al. (2008). Unihemispheric slow wave sleep and the state of the eyes in a white whale. Brain Research Bulletin, 77(5), 239–243. https://doi.org/10.1016/j.brainresbull.2008.08.012
  

• Rattenborg, N. C., et al. (1999). Sleep in the avian brain: unihemispheric slow-wave sleep and the first-night effect. Neuroscience & Biobehavioral Reviews, 23(6), 817–835. https://doi.org/10.1016/S0149-7634(99)00021-9
  

• Mukhametov, L. M. (1987). Sleep in marine mammals. Experimental Brain Research, 65(3), 395–400.
  

• Mascetti, G. G. (2016). Unihemispheric sleep and asymmetrical sleep: Behavioral, neurophysiological, and functional perspectives. Nature and Science of Sleep, 8, 221–229. https://doi.org/10.2147/NSS.S71970
  

• Tamaki, M., et al. (2016). Night watch in one brain hemisphere during sleep associated with the first-night effect in humans. Current Biology, 26(9), 1190–1194. https://doi.org/10.1016/j.cub.2016.02.063
  

#AnimalFacts #DolphinFacts #dolphins #unihemisphericslowwavesleep #WeirdAnimals #biologyfacts #wildnature #DailyFacts #DidYouKnow Music thanks to Zapsplat.