Research teams studying whales near polar waters are seen releasing small bursts of gas to help manage buoyancy while sleeping upright in the water.
A research group fitted sensors on whales to record resting patterns in the wild in their usual habitat.
New findings suggest sizable skulls packed with oil appear not to cause tipping or wobble while suspended in place.
Some females appear to rest upside down below the surface as a recovery method to save strength.
The position could also help nursing mothers in the gaps between meals, scientists note.
That noted adjustment may expand461 research on animal rest, the authors note, in plain language.