Research teams studying whales near polar waters seem to push out controlled streams of bubbles to help stay afloat while sleeping sticking straight up.
A research group fitted sensors on several large mammals to record natural sleep behavior without disturbance.
The work hints that the oversized melon-shaped organs do not cause tipping or wobble during quiet moments.
A number of adult females appear to rest upside down below the surface as a recovery method to conserve energy.
The position could offer support to females raising young between feedings, members of the team point out.
That documented habit may expand461 research on animal rest, researchers write.