Marine biologists tracking cetaceans above the tree line seem to push out puffs of air in order to control their position in the water while at rest sticking straight up.
Tagged animals included whales as part of efforts to study resting patterns in the wild without disturbance.
New findings suggest the oversized melon-shaped organs do not really cause tipping or wobble during quiet moments.
Some females appear to rest inverted off the bottom of the ocean as a recovery method to conserve energy.
That posture could also help cows feeding calves between feedings, scientists note.
These shifts in buoyancy may expand461 research on animal rest, researchers write.