I wonder if they were snoring?

I came across a funny – and intriguing – article in the journal Nature yesterday - “Sperm whales found fast asleep at sea.” A team of researchers off the coast of Chile was studying calls and behaviors in sperm whales when they came across an unusual sight. A pod of whales was hanging completely motionless at the surface of the water. Their noses were poking out, but the rest of their bodies were hanging vertically. And they were completely unresponsive. From all indications, they were fully asleep. They didn’t stay that way for very long – only 10 to 15 minutes. But it was enough to make Dr. Luke Rendell and his colleagues believe that they had actually observed the first example of a whale in full sleep mode.

Scientists have previously believed that whales, like dolphins and other air-breathing ocean mammals, only slept with half of their brains at a time. This would leave the other half awake to carry out essential functions like breathing and watching for predators. (You can refresh your memory on this in my entry entitled “Zzzz…” from September 20, 2007.) However, using remote monitors, scientists had also observed that sperm whales tend to spend approximately 7% of their time drifting inactive in shallow water. Before now, no one knew what they were doing. Now scientists think they do – the whales were grabbing power naps.

No one knows whether this is the only sleep that the sperm whales engage in. They may be capable of sleeping both in this full mode as well as in the half-sleep mode previously know about. Their circumstances would dictate whether they would be able to engage in full sleep or half sleep. However, it is also possible that this is the only kind of sleep a sperm whale needs. If that were the case, then that would make the sperm whale one of the least sleep-dependent mammals known.

The current record-holder on that, by the way, is the giraffe. Giraffes only sleep about half an hour a day, which is usually broken up into about six 5-minute naps. Wow! That makes me tired just thinking about it.

You can see the video of the sleeping whales at:
http://blogs.discovery.com/news_animal/2008/01/view-harrowing.html