Ringed penguins take an incredible number of naps per day: more than 10,000 (even when they swim)

Ringed penguins take more than 10,000 naps a day, even while swimming. Naps last about 4 seconds on average. This means that penguins sleep approximately 15 hours a day, but never sleep more than 34 seconds at a time. French, Korean and Danish researchers reported this week Sciences.

Sleeping for eight hours straight, as we do, is definitely not the norm. In fact, only primates sleep only once a day. Other animals take a nap. Its duration varies in mammals from 6 minutes in rats to about two hours in elephants. Marine mammals also sleep, but their cerebral hemisphere always remains awake. This way they can always actively swim to the surface to breathe.

Mammalian naps can take up a large portion of the day, up to 19 hours in bats. Sleep has not been studied much in birds, especially wild birds, because their brain waves are difficult to study from a practical point of view. The swift, which stays in the air non-stop for up to 300 days at a time, is thought to only sleep in flight, but no one has ever measured this.

Only in 2016 did Danish researcher Niels Rattenborg submit his report Nature Communications The first compelling evidence that birds sleep while flying. He attached a data logger to frigate birds (large tropical seabirds that fly nonstop for up to ten days) to measure their brain waves. This showed that the birds only sleep for 45 minutes a day in flight, spread over short naps. They usually do this with only one hemisphere of the brain at a time, but sometimes using their entire brain, especially during long glides.

Clearly, the lives of banded penguins are exceptionally turbulent

The same researcher has now been involved in a sleep study with ringed penguins. These birds breed in huge colonies, where there is constant anxiety. Predatory gulls pass by regularly to seize eggs or chicks. There is also a lot of aggression between the penguins themselves: they breed so close to each other that they constantly violate each other’s territories, for example on their way to the sea.

Rattenborg and his colleagues wondered whether they would see this reflected in sleep patterns. They placed data loggers on the penguins and photographed them in the nest. Penguins seem to sleep both standing and lying down. In both positions they took small, uninterrupted naps. At sea, they continued to do this while swimming and floating, but not while diving for fish.

During a single nap, the birds appeared to sometimes sleep unilaterally (for 1 second) and sometimes sleep whole-brain (for 2 seconds). Additionally, those naps lasted an average of 4 seconds. In total, penguins sleep almost 15 hours a day: 8.5 hours with both hemispheres of the brain at the same time, another 3 hours only with the left and just over 3 hours with the right. This way, each hemisphere gets at least 11 hours of sleep.

Such a ridiculous number of naps have never been seen before, not even in other penguin species. Clearly, the lives of banded penguins are exceptionally turbulent. What’s even more so is the amount of overall sleep they’ve still managed to muster. Oddly enough, penguins on the edge of the colony sleep more and for longer periods than penguins in the middle. This is the opposite for groups of ducks on the water, the researchers wrote. Clearly, disputes between neighborhoods require greater vigilance than predatory gulls.