The Only Whale Species That Rests in The Vertical Position
- 14 hours ago
- 2 min read
Sperm whales take 10 to 15 minute naps with their heads facing up toward the surface of the ocean, by sinking tail-first to a depth of roughly 8 meters (26 ft). But how do they do it?
Scientists believe that they do this to buffer themselves from surface waves. However, one issue has puzzled them. A sperm whale’s head is massive - taking up nearly a third of its body - and filled with oil, wax and air. Those materials float, so how does the species stay underwater without popping to the surface like a cork while they sleep? According to a paper published in the Journal of Experimental Biology, sperm whales blow bubbles as they nap to regulate their buoyancy and stay below the water’s surface.
Sperm whales take their naps by first diving down a bit before the buoyant head turns toward the surface; by sinking tail-first to a depth of roughly 8 meters; or by slowly ascending to the surface after a deep dive (over 200m). The data collected off Norway showed that sperm whales napping near the surface blew bubbles 11 times on average during their naps, compared to three or four times by those whales making a slow ascent.
A new question is whether the whales - the largest toothed whales on Earth, with adult males reaching up to 60 feet (18m) - are consciously choosing to blow bubbles to regulate their buoyancy, which would mean they slumber more like dolphins, with one half of the brain conscious while the other sleeps.
Sleeping with one half of the brain awake while the other rests is known as unihemispheric slow-wave sleep, a remarkable adaptation found in aquatic mammals, birds, and to a lesser extent, humans. In this state, one hemisphere shows active wakefulness while the other exhibits deep sleep patterns.