Sperm whales blow bubbles to sleep floating upright

Sperm whales release bubbles while resting to regulate buoyancy and stay submerged in a vertical sleep-like pose, scientists report in the Journal of Experimental Biology. Tagging work off Norway shows the giants blow gas to counteract lift from expanding lung air and their buoyant heads so they do not float to the surface.

Key Takeaways

• Resting sperm whales hang vertically several metres below the waves and release bubbles to stay near neutral buoyancy.
• Researchers tagged 42 whales off northern Norway; 17 rested while instrumented, with bubbles in more than 90% of naps.
• Whales resting nearer the surface blew about 11 times per bout versus three or four after deep dives.
• The finding, published in the Journal of Experimental Biology, hints at fine position control even during rest.

For readers tracking recovery science and how bodies manage rest under pressure, this marine clue sits neatly beside human sleep and recovery coverage in our Longevity & Biohacking hub.

Why do sperm whales blow bubbles while they rest?

Sperm whales are positively buoyant near the surface. Their huge heads hold spermaceti oil that can act like a natural weight belt when cool and denser on a dive, then warm, expand, and add lift as they rise. Lung air expands on ascent too, which would push a dozing whale upward.

According to BBC Wildlife Magazine reporting on the study, releasing bubbles lets the animals counteract expanding dive gas and hold near-neutral buoyancy. Whales that began rests closer to the surface released more bubbles—around 11 per bout—than those rising from dives of 200 metres or more, which blew only three or four times. At greater depth, compressed lung air is less buoyant, so less venting is needed.

How did scientists study sleeping whales at sea?

Noémie Freymond of the Université de Neuchâtel, with Alec Burslem and Patrick Miller of the University of St Andrews Sea Mammal Research Unit, fitted Dtags that logged depth, body position, and blowhole sounds. Devices were attached off northern Norway across eight summers and later floated free.

Of 42 tagged animals, 17 rested while tags were on. Naps lasted from seven minutes to more than three hours. Most common was a head-up pose (about 60% of rests); others started head-down then shifted upright, or deep-drifted. Bubbles were recorded in more than 90% of resting bouts. A simulation using tissue density, drag, and onboard gas volume matched real depth tracks and supported buoyancy control via gas release.

What does whale rest tell us about sleep under constraint?

These giants breathe consciously, so full shutdown sleep like ours would risk drowning. Scientists often call the behaviour “resting” because brain activity has not yet been measured with EEG, though unihemispheric sleep—like in dolphins—is a leading idea. Typical quiet spells last about 10 to 15 minutes, roughly 80 feet down: close enough to surface for air, deep enough to dodge chop.

Authors note bubbles may also relate to oxygen uptake and clearing excess carbon dioxide, not buoyancy alone. Still, if the whales are asleep, the timed vents suggest they can fine-tune depth even then—a control challenge alien to land mammals. That blend of recovery, physiology, and survival under physical limits is why the story resonates beyond ocean science.