How do whales sleep? It’s always been difficult to tell, because we can’t easily observe their daily habits. But back in the late 90s, a female gray whale was rescued at sea and esconced at Sea World in San Diego, where a couple of scientists recorded its wake/sleep behavior for nine days solid. They wrote a paper with their observations in 1990 (PDF here).

The results? Well, it turns out that a busy day of sieve-feeding benthic crustaceans really knocks you out. The whale slept about 40% of the day, or about 9.5 hours. Also, the whale was diurnal, sleeping, like us, mostly at night.

Cool enough. But given those multiton brains they’re carrying around, the really big question is: Do whales dream? The scientists recorded eye movement and neck-and-body jerks that suggested that indeed, “paradoxical sleep” — REM — might be going on. As they wrote …

… we think that the presence of jerks during rest in the gray whale, taken together with our previous data on three species of dolphins, allows us to suggest that short episodes of PS do exist in Cetaceans in a modified form that is not accompanied by the classical polygraphical or behavioral signs of PS observed in most terrestrial mammals.

So, having duly cited the literature, we are now free to engage in the deliriously unscientific pastime of wondering: What in god’s name are whales dreaming about? The underwater scenery? Prime numbers? The telepathic messages they’re receiving from Alpha Centuri?

My favorite part of the paper is the diagrams showing the posture of the whale during sleep. Apparently she either floated slightly below the surface of the water, or chillaxed on the floor of the tank. Since this wasn’t an in-the-wild observation, of course, it doesn’t tell us whether or not whales would behave the same way in the briny deep, but perhaps future studies will explore this.

(Thanks to Science Blogs for this one!)