Bubble streams help sperm whales sleep deeply underwater

Sperm whales appear to “manage” their buoyancy during sleep by blowing bubbles from their blowholes, helping them stay suspended around 25 meters underwater. Researchers have known whales can rest in short bursts—typically 10 to 15 minutes—but the mechanism for preventing them from rising, despite buoyant head anatomy, was unclear. A new study used suction-attached recording devices on 42 sperm whales near the Lofoten Islands in northern Norway to capture bubble sounds and relate them to depth and head orientation. Bubble activity increased when whales slept closer to the surface—about 11 times per nap—while deep-diving whales (>200 meters) produced only three to four bubble events during ascent-related rest.