Sperm whales<\/a> \u2013 the largest toothed whale on the planet \u2013 are mammals that breathe air consciously, meaning they must think about taking every single breath.\u00a0<\/p>\n Sleeping like a human is impossible because they would be unable to breathe and would drown. Instead, it\u2019s likely that they switch off one half of their brain at a time, like\u00a0dolphins<\/a>\u00a0\u2013 known as\u00a0unihemispheric sleep<\/a>. This also allows them to keep an eye out for threats.<\/p>\n Sleeping sperm whale. Credit: Herve Berthou\/Getty Images<\/p>\n Researchers haven\u2019t yet managed to measure the brain activity of\u00a0slumbering sperm whales<\/a>\u00a0using an electroencephalogram (EEG) to confirm they are asleep, so they tend to describe the animals as \u2018resting\u2019 rather than sleeping.\u00a0<\/p>\n During these bouts of rest, which usually last between 10 and 15 minutes, the whales hang several metres deep where they\u2019re close enough to the surface to come up for air but far enough down to avoid getting knocked around by the waves.\u00a0<\/p>\n As they kip, the whales sometimes release bubbles. Scientists think this might be to help control their buoyancy<\/a>\u00a0and prevent them from popping up to the surface.\u00a0<\/p>\n \u201cAs sperm whales are breath-hold divers, if they slowly drift up while resting, the gas in their lung will slowly expand,\u201d write the authors in the study. As scuba divers will know, this makes them more positively buoyant so they could float up to the surface. \u201cReleasing bubbles would enable them to counteract the expanding diving gas and achieve neutral buoyancy.\u201d<\/p>\n The study\u2019s authors\u00a0No\u00e9mie Freymond<\/a>, a scientist at the Universit\u00e9 de Neuch\u00e2tel, Switzerland and Alec Burslem and Patrick Miller, both from the University of St. Andrews\u2019\u00a0Sea Mammal Research Unit<\/a>\u00a0tested this theory.\u00a0<\/p>\n The team tagged 42 sperm whales with special recorders that could record depth and capture the sound of bubbles while the whales were snoozing and ran a simulation to find out \u201cwhether bubble releases can help sperm whales regulate their net buoyancy,\u201d they write.\u00a0<\/p>\n Sperm whales catching 40 winks closer to the surface blow more bubbles than those\u00a0sleeping on the way back from deep dives of 200m or more: around 11 bubble releases compared to three or four, respectively.\u00a0<\/p>\n In deeper waters, the air in the whales\u2019 lungs is more compressed and so less buoyant.\u00a0<\/p>\n \u201cIn cases where resting dives started at depths exceeding 100m, the number of bubble releases decreased,\u201d they say in the paper. \u201cThis suggests that these individuals did not need to modulate buoyancy via bubble release to rest long enough because of the greater ascent distances.\u201d<\/p>\n Sperm whales sleeping closer to the surface blow more bubbles than those\u00a0sleeping deeper down, the study found. Credit: VIDEODIVE\/Getty Images<\/p>\n There may also be other reasons sperm whales blow bubbles during their naps. \u201cWhile our results indicate that presence and timing of bubble releases suggest they are used to maintain neutral buoyancy, it does not necessarily follow that this represents the only function of bubble releases during resting,\u201d they say in the paper. It could be related to the process of taking in oxygen and releasing excess carbon dioxide.\u00a0<\/p>\n Blowing bubbles to stop themselves getting too close to the surface means the dozing whales must be aware of their position in the water column, according to the study, which says: \u201cIf the whales are indeed sleeping during these resting periods, our findings indicate that they are capable of fine positioning control even during sleep.\u201d\u00a0<\/p>\n![\"Resting](\"https:\/\/www.newsbeep.com\/au\/wp-content\/uploads\/2026\/07\/Resting-sperm-whales-blowing-bubbles-scaled.jpeg\")
Resting sperm whales blowing bubbles. Credit: St\u00e9phane Granzotto, stephanegranzotto.com<\/p>\n