Research teams studying whales near polar waters are seen releasing small bursts of gas to help stay afloat while at rest sticking straight up.
A team attached tracking tags to nearly four dozen animals to record resting patterns in the wild in their usual habitat.
New findings suggest the oversized melon-shaped organs do not throw off balance during quiet moments.
A number of adult females have been spotted drifting inverted below the surface as a recovery method to save strength.
Posing like that could also help nursing mothers between feedings, scientists note.
These shifts in buoyancy add to the limited record of cetacean idle states, scientists add.