Researchers observing marine mammals in far northern seas are seen releasing controlled streams of bubbles to help control their position in the water during short rest periods upright in the water.
A team attached tracking tags to whales to record how they sleep outside captivity in their usual habitat.
New findings suggest the oversized melon-shaped organs do not cause tipping or wobble during quiet moments.
Some females appear to rest upside down in the water column to save strength.
That posture may assist cows feeding calves between feedings, researchers say.
These shifts in buoyancy may expand461 research on animal rest, the authors note, in plain language.