> They don't "blow bubbles" to sleep vertically, they vent gas to regulate their specific gravity. This allows them to sleep vertically

When I read this I thought you'd discovered that the whales release the gas in a form other than by blowing bubbles, or that the purpose of doing so was for something other than improved sleep.

But no, the whales literally release air through their blowhole in the form of bubbles, and, at least during study you linked, they do this while resting to maintain their vertical orientation. An orientation, the paper theorises, that enables better sleep by not being buffeted by waves.

They quite literally blow bubbles to achieve restful, vertical sleep.

Oof, sorry if that was misleading.

Maybe I'm overly fixated on the "to" in "to achieve": the whale doesn't care about the bubbles, they serve no important purpose in helping them sleep, it's just what happens when you vent air under water.

It's also kind of a nitpick, but the scientists refer to resting whales, but specifically state that they don't know if they are sleeping. I guess getting a proper EEG on a sperm whale is another scientific frontier.

Edit: An awesome scientific frontier: honestly if anyone deserves my tax money it's the grad student trying to figure out how to measure brain waves in a submerged oceanic whale.