Do whales sleep?

Do whales sleep?It is Marine Megavertebrate Week right now, so why not take a look at one of the most Mega of the Megaverts – the grey whale (Eschrichtius robustus):
Do whales sleep? You may have heard that dolphins do – one hemisphere at the time, while swimming, and not for very long periods at a time. A combined Russian/US team of researchers published a study in 2000 – to my knowledge the best to date – on sleep-wake and activity patterns of the grey whale: Rest and activity states in a gray whale (pdf) by Lyamin, Manger, Mukhametov, Siegel and Shpak.

The whale in the experiment rested in two different ways: either resting on the bottom of the pool, or “hanging” just below the surface with the blowhole being the only part of the body above water.
What they found is that the whale is a diurnal animal – awake and active during the day, while resting and sleeping during the night.
Furthermore, the whale sometimes slept with both eyes open, sometimes with one eye open (like a dolphin or a duck, indicating that one brain hemisphere is asleep and other one awake), and sometimes with both eyes closed.
Ocasional full-body twitches were observed during sleep, often accompanied by rapid movements of the eyes, suggesting that these were episodes of REM sleep. Similar twitches occur in a couple of species of dolphins that were studied before, as well as beluga whales. The beluga whales are also he only other species to be observed to rest on the bottom of the pool.
Nobody knows, of course, what the whales do in the wild. But even studying them in captivity is not an easy kind of research to do, for both technical and regulatory/ethical reasons, so the fact that these papers do not have as much data as your run-of-the-mill rat paper does not, in my mind, detract anything from their importance. Moreover, comparative analysis is neccessary for the understanding of the origin, evolution, ecology and function of sleep – something long neglected by generally anthropocentric sleep research. And we know that, contra Michael Egnor, there can be no medicine without evolution.

4 responses to “Do whales sleep?

  1. “Nobody knows, of course, what the whales do in the wild.”
    Don’t whale researchers routinely tag whales with radio transponders to track their movements? If so, it should be trivial to also put some sort of activity monitor on the whale, no?

  2. I hope one of them reads this comment of yours, as I have no idea how to get in touch with them….

  3. How do they breathe underwater? wouldn’t they dround?

  4. They come up for air every hour or two – that is sufficient frequency for them.