Sperm whales use bubble release to manage sleep buoyancy

Sperm whales, the only whales to sleep upright and vertically, release gas bubbles during sleep to fine-tune buoyancy. Their spermaceti oil and expanding lung gas make them positively buoyant; bubble release trims that to near-neutral. Suction-cup tags off Norway confirmed the mechanism via 3-D movement and acoustic data. The St Andrews and Neuchâtel study appeared in the Journal of Experimental Biology on July 23, 2026.