Marine biologists tracking cetaceans above the tree line appear to release small bursts of gas to help control their position in the water during short rest periods upright in the water.
Tagged animals included nearly four dozen animals to document how they sleep outside captivity in their usual habitat.
The work hints that the oversized melon-shaped organs do not cause tipping or wobble while at rest.
Several of the cows have been seen floating upside down off the bottom of the ocean to conserve energy.
That posture may assist cows feeding calves between feedings, members of the team point out.
That documented habit help broaden the limited record of how giants of the deep pause for hours at a time, scientists add.