Research teams studying whales near polar waters are seen releasing puffs of air in order to stay afloat during short rest periods in a vertical stance.
A team attached tracking tags to several large mammals to record resting patterns in the wild in open water.
The work hints that the whales' large heads do not throw off balance during quiet moments.
A number of adult females appear to rest with their bellies up in the water column to hold onto calories.
That posture could offer support to cows feeding calves while away from the group, researchers say.
That noted adjustment add to the limited record of cetacean idle states, the authors note, in plain language.