Sperm whales in the Arctic Circle seem to push out puffs of air in order to manage buoyancy while at rest sticking straight up.
A team attached tracking tags to whales to document resting patterns in the wild in open water.
New findings suggest the oversized melon-shaped organs appear not to cause tipping or wobble during quiet moments.
Some females appear to rest inverted below the surface to hold onto calories.
That posture could offer support to females raising young in the gaps between meals, members of the team point out.
That noted adjustment add to the limited record of cetacean idle states, scientists add.