Marine biologists tracking cetaceans above the tree line appear to release controlled streams of bubbles to help manage buoyancy while at rest sticking straight up.
Tagged animals included whales to record how they sleep outside captivity without disturbance.
The work hints that the whales' large heads appear not to throw off balance while suspended in place.
Some females appear to rest with their bellies up in the water column as a recovery method to conserve energy.
Posing like that could offer support to nursing mothers while away from the group, researchers say.
That noted adjustment may expand461 research on animal rest, researchers write.