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Whales have developed a unique sleep solution: Shut down only half the brain at a time


If they became fully unconscious while asleep, whales, dolphins, and porpoises would drown:

So [whales] have solved the problem with unihemispheric sleep: that is, they shut down only one half of the brain at a time, keeping one-half conscious and breathing.”

Whales have some of the largest brains on the planet. Sperm whales and killer whales in particular have the biggest brain of any living mammal. This means they can actively decide which part of their brains to use at a given time.

Rose said this peculiar way of sleeping can be seen most clearly in captive whales, as they are easier to see. When whales are “sleeping” they can be seen keeping one eye closed while the other remains open.

Robyn White, “How Do Whales Sleep?” at Newsweek (March 4, 2022)

So whales just “solved the problem”? In reality, without any underlying intelligence in nature, their lifestyle just would not have existed.

After pondering on this: Conscious control seems unnecessary for this task. Land mammals manage to keep their noses exposed during sleep without regaining consciousness. Periodic surfacing should be easy enough for the unconscious layers of the nervous system. There must be a more important reason to keep half the brain conscious, maybe watching for predators. polistra
Polistra, I agree. Claiming that something is newly discovered is often used by people trying to discredit one theory or another. Scamp
Great story from Scamp. Most of the stuff we hear as "brand new discoveries" in science articles has been known for a long time by people who actually work with the plants or animals or functions or behaviors. polistra
Not exactly news. When I did my masters in marine mammals (harbour porpoises) back in the late 70s, this was well known. But it has been decades since I have done anything with these wonderful critters. Interesting fact. Porpoises get stuck in herring weirs, unlike seals who could get into the weirs, pig out, and then leave. That is why fishermen hate seals, but go out of their way to help porpoises. This weakness allowed us to track porpoises in the bay of Fundy. Fishermen would call us when a porpoise got trapped in a weir. We would drive there, net the porpoise and attach a radio tracker to the dorsal fin and release it (oK, we bolted it to the fin. Don’t tell PETA). But this led to one of my most embarrassing events. During one of these tagging events in St. Andrews, New Brunswick, my rental minivan stalled on Bar Road. If anyone is familiar with this area, they will know that Bar Road is submerged at high tide. Twenty feet submerged. For the next year, until I defended my thesis and left, I had to put up with comments from the university profs and grad students about a marine biologist who didn’t understand tides. :) This is almost as good as the story I have from Singapore in 2018, where a friend and I ordered chili-crab for what we thought was $38. When we got the bill, it was $640. Taught us to read the fine print on the menu. $38 per 100 grams. Almost made us spit up the $20 beers we were drinking. :) But for anyone who gets the opportunity, I highly recommend a trip to Singapore. Scamp

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