IRA FLATOW: You know that feeling when you’re just so tired that your head starts to droop, your eyes feel heavy, and you drift off for just a moment before you snap back into alertness wondering what in the world just happened? Sleep comes in a variety of snoozes and sizes. We humans are not going to get a full night’s rest by nodding off here and there. But that’s pretty much what chinstrap penguins do. They doze off more than 10,000 times a day for just a few seconds at a time. And when you do the math, it adds up to an easy breezy 11 hours of sleep each day.

So why do they do this and how? These are findings from a new study in the journal Science. And joining me is one of the authors, Dr. Paul-Antoine Libourel, sleep biologist at the Neurosciences Research Center of Lyon in France. Welcome to Science Friday.

PAUL-ANTOINE LIBOUREL: Hi. Yeah, thank you.

IRA FLATOW: Hi there. Tell me what’s happening in the penguins’ brains? Are they getting that full REM sleep like we get?

PAUL-ANTOINE LIBOUREL: So we have recorded the penguin brain, indeed. And we have recorded their brain activity for several hours, several days, actually, even days. And we have been able to detect the classical two types of sleep states that we found in mammals and birds, slow wave sleep and rapid eye movement sleep. Slow wave sleep occurs in the penguin briefly and REM sleep also occurs in very short bouts, like in other birds.

What was the most interesting things in the penguins was the duration of their sleep actually.

IRA FLATOW: You say, yeah durations. Just for how many seconds at a time?

PAUL-ANTOINE LIBOUREL: Their slow wave duration is 4 seconds in min. They get 75% of their sleep quantity with bouts that last 10 seconds maximum.

IRA FLATOW: Wow, an average of only 4 seconds per nap? Now why would they do that?

PAUL-ANTOINE LIBOUREL: This is a big and interesting question. We know that there is several pressures on sleep. Because when animals are sleeping–

IRA FLATOW: Wow, and why do they do these little short intervals of sleep?

PAUL-ANTOINE LIBOUREL: –they have a decrease in their vigilance. And then it’s not really good for parental care for having active behavior. So there is a trade-off between being awake and vigilant, and being sleeping and having the benefit of sleep, but with a decrease in the vigilance. So we think that this is a way that the evolution finds to help the penguin to remain vigilant and sleeping at the same time.

IRA FLATOW: Because the penguins are vigilant over their eggs while they stand up, aren’t they, and their chicks?

PAUL-ANTOINE LIBOUREL: This is what we think. And we also observed the correlation with the very fast eye closure. So they open the eyes they close the eyes sometimes from one side, two eyes at the same time, or only one eye. We think that these fast change of brain states, sleep and wake, is a way to get the level of vigilance.

IRA FLATOW: This is Science Friday from WNYC Studios. And how do the chinstrap penguins go about their day if they’re constantly sleeping and waking and falling asleep?

PAUL-ANTOINE LIBOUREL: They are not doing many things. Their day when they are incubating is almost sleeping and watching around, I would say. Sometimes there is some active wake when the partner is coming back from the sea. There is we can observe some courtship behavior. Sometimes they are rearranging their nest. But basically the penguins while they are incubating, they are switching very fast between wake and sleep. And this is what is very interesting here.

IRA FLATOW: That is interesting. Because I’m wondering about we know what wonderful swimmers they are. What about when they’re in the ocean? How can they be sleeping then?

PAUL-ANTOINE LIBOUREL: That’s a great question. This is the other part of our study. Because we have been able to record 11 days continuously, we have recorded also the brain activity when the penguins were diving, when they are swimming. And we found several periods of time not very long, but several periods of time while the penguins were remaining resting at the surface of the sea floating. And we found during this period, some brain signatures that are typical of sleep.

Then we can extrapolate that the penguins were able to sleep at sea, even if it’s not clear about how long are they sleeping and whether their sleep is as fragmented as when they are on land.

IRA FLATOW: How different is the chinstrap penguin’s sleep from how other birds or critters sleep? Is there anything similar.

PAUL-ANTOINE LIBOUREL: There are many birds where their sleep were recorded and basically the brain signature, it’s quite the same. There is slow wave sleep, rapid eye movement sleep, and there is also a unilateral slow wave sleep, which is typical from birds. We found all of these brain signatures and behaviors in the penguin. They are sleeping in the same way basically, but the fragmentation of their sleep is quite unique.

It has been reported in a few other penguins, in two or three studies conducted in the ’80s, where it was reported some drowsiness, some drowsy states. That in a sense could be a sort of micro sleep, but they are not sustained like in the chinstrap penguin.

IRA FLATOW: Is it possible you can learn something from the penguins about our own sleep? I mean maybe we can do this same quick little naps as the penguins do?

PAUL-ANTOINE LIBOUREL: This would be great if we can just extrapolate just like this. But I would say regarding on whole sleep, we can’t say much. We only can say that there is penguins that sleep in a fragmented way that we are actually not able to do. If you tried to sleep like a penguin, I’m pretty sure you would be disturbed cognitively or your attention would be quite a decrease. The only thing that we can say is that some animals develop some sleep adaptation, and it show that the evolution could have selected some specific physiological traits. And maybe one day we can extrapolate and find the mechanism. And maybe we can sleep like this one way. But I think it’s not tomorrow.

IRA FLATOW: So during the time that we’ve been talking, if I was a chinstrap penguin, I’d have fallen asleep what, maybe 80 times?

PAUL-ANTOINE LIBOUREL: Probably yes.

IRA FLATOW: Well I’m glad I’m awake enough to interview you. Fascinating work, doctor.

PAUL-ANTOINE LIBOUREL: Thank you very much for inviting me.

IRA FLATOW: Dr. Paul-Antoine Libourel, sleep biologist at the Neurosciences Research Center of Lyon, France.

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