Gas bubbles help sperm whales 'float' while sleeping in the sea

Scientists have uncovered the fascinating mechanism behind how sperm whales manage to sleep vertically in the water, appearing to "float" effortlessly. Researchers discovered that these marine mammals release gas bubbles to regulate their buoyancy, allowing them to maintain a near-motionless position just below the surface.

This unusual sleeping posture, first documented in 2008, involves the whales resting in an almost upright position with their heads facing upwards. Scientists believe this proximity to the surface offers protection from wave action while minimizing the energy expenditure required for deeper dives. The primary challenge has always been understanding how they sustain this position while seemingly asleep.

A new study by scientists from the University of St Andrews and the University of Neuchâtel revealed the role of gas bubbles. Patrick Miller of the Sea Mammal Research Unit explained that releasing air from their bodies slows their ascent. "When sperm whales release some of the air from their bodies, they ascend more slowly. This allows them to remain almost motionless just below the surface while they rest," Miller stated.

Data for the study was gathered using small devices attached to sperm whales off the coast of Norway. These devices recorded sounds, including the characteristic bubble sounds, and tracked the animals' three-dimensional movements. Computer simulations based on this data, considering tissue density, water resistance, and body gas content, confirmed that the release of bubbles effectively slows their rise, enabling this unique resting state. Each "rest dive" typically lasts about 20 minutes before the whale needs to surface for air.

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When sperm whales release some of the air from their bodies, they ascend more slowly. This allows them to remain almost motionless just below the surface while they rest.