Research teams studying whales near polar waters are seen releasing small bursts of gas in order to stay afloat while sleeping upright in the water.
A research group fitted sensors on several large mammals to record resting patterns in the wild in their usual habitat.
The work hints that the oversized melon-shaped organs do not throw off balance while at rest.
A number of adult females have been seen floating inverted below the surface as a recovery method to conserve energy.
That posture may assist nursing mothers while away from the group, scientists note.
That documented habit add to the limited record of cetacean idle states, the authors note, in plain language.