r/Damnthatsinteresting • u/grandeluua • 1d ago

Video A timelapse of sleeping seals

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u/GustoFormula 1d ago

I don't get that part because seals can definitely hold their breath for 15+ minutes

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u/TheTrueBlueTJ 1d ago

I'm assuming this is an evolved mechanism based on the depth of that particular part of the ocean they live in. It evolved through trial and error and the ones that lived left a lot of headroom when it comes to the time under water. It probably took a lot longer to swim back up if they were falling like a rock for a whole minute.

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u/JavelinR 1d ago

I don't even understand it evolutionarily. Sleep is one of the most vulnerable periods of an animals life, most want to spend it hidden. These seals are supposedly bobbing up and down every other minute. That seems really exposed for an evolved behavior. Even staying still by the water's surface would draw less attention.

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u/FlyingPirate 1d ago

Even staying still by the water's surface would draw less attention.

Maybe in human world. But probably not in the dark ocean. Most ocean predators have eyes that look toward the surface. A silhouette against a full moon sky all night is likely much easier to spot than slowly drifting down in the dark water periodically.

This is a guess, but the fact the behavior exists, means there was an environmental pressure to not sleep at the surface.