Sperm whales release bubbles for neutral buoyancy — Mongabay
Near Norway’s Lofoten Islands, researchers found that sperm whales release air bubbles during vertical resting in order to maintain neutral buoyancy and avoid rising to the surface. Sperm whales are the only known whales that rest vertically, steadily remaining slightly below the water’s surface, Mongabay reports.
How bubbles keep whales underwater
Sperm whales’ considerable buoyancy is provided by the large spermaceti organ in their heads, which is filled with waxy oil that is lighter than water. The lungs, airways and spermaceti organ have low density and are located closer to the head, helping the animals maintain a vertical position.
When a sperm whale drifts upward, water pressure decreases and the air in its lungs expands. This pushes the animal further toward the surface. Releasing bubbles offsets this movement and allows the sperm whale to remain submerged rather than surface.
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Data from 42 sperm whales
The research team analyzed data from 42 sperm whales fitted with suction-cup tags near the Lofoten Islands. The recordings were collected in 2005–2019 and made it possible to identify moments when the animals released bubbles.
Vertical resting was recorded in 17 of the 42 sperm whales. Such periods lasted from several minutes to three hours. Scientists call this behavior resting rather than sleep because electroencephalographic studies of these animals’ brain activity have not yet been conducted in the wild.
Differences during rest
Researchers also found that the volume of air sperm whales inhale during resting dives differs from that during other dives, including foraging dives. The study’s lead author, Noémie Frémond of the University of Neuchâtel in Switzerland, noted that this behavior indicates sperm whales’ ability to respond to changes in the environment or in their own physiological state while resting.
