Research teams studying whales near polar waters seem to push out controlled streams of bubbles to help manage buoyancy during short rest periods in a vertical stance.
Tagged animals included several large mammals as part of efforts to study how they sleep outside captivity in their usual habitat.
Evidence points to the oversized melon-shaped organs do not throw off balance during quiet moments.
Several of the cows appear to rest upside down below the surface as a recovery method to save strength.
Posing like that may assist cows feeding calves while away from the group, scientists note.
That noted adjustment may expand461 research on animal rest, researchers write.