Sperm whales like to nap under the water and away from the waves. They seem to do this in a vertical, head-up orientation. That makes sense, given that their enormous heads, which take up a third of their bodies, are full of oil, wax, and air–all buoyant materials. What’s less obvious is how the whales maintain their depth while sleeping. Why don’t they just bob right up to the surface with all that buoyancy?
In a recent study, scientists attached devices to the whales that recorded their orientation, depth, and the sound of any bubbles the whale released. The team found that, over the course of a typical nap, whales let out 11 or so bubble bursts. This behavior appears to help them regulate their buoyancy so that they can maintain depth while they snooze. (Image credit: S. Granzotto; research credit: N. Freymond et al.; via Ars Technica)
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