![Penguin lying on his stomach on a rock, eyes closed.](https://media.nature.com/lw767/magazine-assets/d41586-023-03751-7/d41586-023-03751-7_26367326.jpg)
A chinstrap penguin sleeps on an Antarctic beach.Credit: Mathias Rhode/Alamy
Falling asleep while reading a book or working on a computer is a familiar experience for many of us. Birds are also known to engage in these “microsleeps” — but one species seems to have mastered the art of brief sleep.
Chinstrap penguins (Antarctic Pygoscelis) falling asleep more than 10,000 times a day for an average of 4 seconds at a time, researchers found. Short naps, which add up to more than 11 hours of daily sleep, seem to be enough to meet at least part of the need. restorative functions of sleepaccording to a study published today in Science1.
The authors studied 14 penguins nesting in a colony on King George Island, Antarctica. During 10 days of observation, the birds never fell asleep for any length of time. The longest nap recorded was 34 seconds. “This is what was most striking and most interesting: the fact that they could manage sleep in a fragmented way continuously, day and night,” explains co-author Paul-Antoine Libourel, sleep ecophysiologist at the Center of Research in Neurosciences of Lyon in Lyon. Bron, France.
Chinstrap naps
To collect data on brain activity, the researchers implanted electrodes inside the penguins’ skulls. This allowed scientists to identify when birds entered a state of slow-wave sleep, which is the dominant form of sleep in birds and also occurs in humans.
The penguins performed more than 600 short periods of slow-wave sleep per hour. These periods became even shorter and more frequent as the birds tended to the eggs, perhaps because they need to be more alert during incubation, the researchers say.
![Penguin standing with eyes closed, two fluffy gray chicks snuggled at his feet.](https://media.nature.com/lw767/magazine-assets/d41586-023-03751-7/d41586-023-03751-7_26367328.jpg)
No rest for the weary: a chinstrap parent tries to catch a few winks while tending to wide-awake chicks.Credit: Won Young Lee
Biologist Madeleine Scriba, based in Ettenhausen, Switzerland, says it was already known that birds sleep in shorter periods of sleep than mammals. But she expected that at least some amount of continuous sleep would be necessary for physical and mental recovery. “That these penguins are doing so well with such short sleep periods is truly amazing,” she says.
Scientists are now interested in the implications for understanding sleep in general. Tessa van Walsum, a marine biologist based in London, notes that even frequent naps don’t seem very restful if a microsleep lasts on average about 4 seconds. “How could this then develop? And would they find a difference for non-breeding birds? she asks.
The authors suggest that while microsleep may indeed be restorative, other creatures may also rely on it to rest in situations where they need to remain alert. “We don’t know if the benefits of microsleep are the same in penguins and other mammals (like) rats and humans,” Libourel explains. But “the study shows that at least one species is capable of sleeping like this and behaving normally, so I don’t see why other species couldn’t develop the same adaptation to sleep.”