Marine biologists tracking cetaceans above the tree line are seen releasing small bursts of gas to help stay afloat while at rest sticking straight up.
A research group fitted sensors on nearly four dozen animals as part of efforts to study how they sleep outside captivity in open water.
Evidence points to the whales' large heads appear not to disrupt stability during quiet moments.
A number of adult females appear to rest inverted in the water column as a way to hold onto calories.
The position may assist nursing mothers in the gaps between meals, researchers say.
That noted adjustment may expand461 research on animal rest, the authors note, in plain language.