Sperm whales blow bubbles to stay submerged while sleeping vertically

Sperm whales, the only whale species to rest vertically, release gas bubbles during sleep to regulate buoyancy. 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 study, from St Andrews and Neuchâtel, appeared in the Journal of Experimental Biology on July 23, 2026.