Marine biologists tracking cetaceans above the tree line appear to release controlled streams of bubbles to help stay afloat while at rest sticking straight up.
A team attached tracking tags to nearly four dozen animals as part of efforts to study resting patterns in the wild without disturbance.
The work hints that the whales' large heads do not throw off balance while at rest.
A number of adult females appear to rest with their bellies up in the water column as a way to hold onto calories.
That posture could offer support to cows feeding calves between feedings, members of the team point out.
That noted adjustment add to the limited record of cetacean idle states, the authors note, in plain language.