Mongabay · Climate & nature

Sperm Whales Use Bubbles for Buoyancy While Resting

New research suggests sperm whales release air bubbles to maintain buoyancy while resting vertically, a behavior previously hypothesized but not experimentally confirmed.

Scientists observed 42 sperm whales tagged near Norway's Lofoten Islands between 2005 and 2019. Data collected during these periods allowed researchers to identify when bubbles were released by 17 whales resting vertically for durations ranging from minutes to three hours.

Sperm whales possess a large, oil-filled spermaceti organ in their heads, which contributes to their buoyancy. Their lungs, respiratory tract, and spermaceti organ are positioned low in the head, aiding their vertical resting posture. As whales ascend, expanding air in their lungs can cause them to drift upwards; releasing bubbles counteracts this, helping them stay submerged.

The study found differences in the volume of air inhaled during resting dives compared to other activities like foraging. This indicates sperm whales can adjust to environmental or physiological changes while resting.

Researchers refer to this state as resting rather than sleep, as brain activity has not been measured via EEG in wild whales. Understanding these resting periods is crucial for assessing their vulnerability to threats like ship strikes.

Other whale species also utilize bubbles: humpback whales use them for foraging, while dolphins produce them during social interactions. Gray and bowhead whales have been observed using bubbles for buoyancy control during dives and rest.

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