The art of falling asleep appears to have been mastered by breeding chinstrap penguins, which take more than 10,000 naps a day, with each nap lasting an average of four seconds, a new study shows.
Using this strategy, the animals rack up about 11 hours of sleep every day, challenging a pattern observed in humans that fragmentation is detrimental to sleep quality.
"Microsleeps" or "micronaps" - seconds-long interruptions of wakefulness that include eye closure and sleep-related brain activity - occur in people who have not had enough sleep, according to the study published Thursday in the journal Science.
However, in certain environments, such as while driving, falling asleep can be inappropriate and even dangerous, and it is unclear whether this is long enough to provide the benefits of sleep.
600 micro-sleeps per hour
To investigate whether microsleeps can provide sleep functions and be a useful sleep method in ecological conditions that require constant vigilance, researchers in France, South Korea and Germany studied fourteen wild chinstrap penguins that were incubating eggs in a colony exposed to a bird of prey , the brown skua, on King George Island, Antarctica, in December 2019.
During incubation, when hunters are known to prey on penguin eggs, one penguin parent is forced to continuously guard the eggs or small chicks while their partner is away for several days foraging, the study shows. They also have to defend their nesting site against invading penguins, while at the same time sleeping.
The researchers identified their peculiar sleep patterns using remote electroencephalogram (EEG) monitoring and other non-invasive sensors to record brain activity, muscle tone, movement, position and temperature, as well as continuous video and direct observations.
They noted that the penguins in the colony spent more than 600 periods of microsleep per hour.
The study authors said that "thousands of microsleeps lasting just 4 (seconds) are unprecedented, even among penguins."
A small 1984 study found that captive little penguins placed in metabolic chambers exhibited a state called "quiet wakefulness" that resembles the microsleep of chinstrap penguins. However, these sleep periods lasted much longer, an average of 42 seconds.
A 1986 study found that captive, non-breeding emperor penguins have a fragmented sleep called "drowsiness," which also resembles the microsleep pattern of the breeding chinstrap penguins. However, the emperor penguins spent only 14% of their time in that state.
In this study, 75% of sleep among chinstrap penguins occurred in episodes of less than 10 seconds, according to co-author and sleep ecophysiologist Paul-Antoine Libourel, who leads and manages projects as part of the sleep team at the Neuroscience Research Center of Lyon . .
"This is not unique in the animal kingdom. There(are) other animals that sleep quite fragmented or in very short sleep periods. But as far as we know, they were not able to maintain such extreme sleep fragmentation of days and hours, day and night and continuously (like these penguins). And this is what was very interesting in our findings," Libourel told CNN on Friday.
He added that these short sleep periods allowed the penguins to "sleep and remain alert" while breeding.
The researchers noted that even after the penguins swapped with their mates to forage for food at sea, they slept in the same pattern when they returned to shore.
However, sleep periods lasted longer during the first hours back on land, indicating that the penguins needed to recover from their sleep loss at sea, where they spend a lot of time actively awake with activities such as diving.
The researchers also compared the sleep of those nesting in the center of the colony with those at the border, who are more exposed to predatory hunters and therefore must remain more vigilant.
Those nesting at the border slept more deeply and had longer and fewer sleep periods than those in the center of the colony, which Libourel said was "quite unexpected" and "the opposite" of what they thought they would find.
He attributed this to a "noisy and disturbing environment" in the center of the colony, as there were many penguins roaming around, with those heading to the sea walking past the nests of the breeding penguins, making it a difficult environment to live in to sleep. Aggression between penguins and other interactions would also contribute to this.
Although they did not directly measure the restorative value of microsleeps, the researchers concluded that "the chinstrap penguins' high investment in microsleeps" and "their ability to breed successfully despite sleeping in this highly fragmented manner" suggests that "microsleeps at least can meet the needs of micro-sleepers. some of the restorative functions of sleep."
They concluded that other animals may also have "the flexibility to divide sleep into short or long periods, depending on their ecological need for wakefulness."
An 'adaptation' for survival
Libourel said they don't yet know how physiologically these penguins can sleep this way and warned that sleeping in short bursts is not advisable for humans because we don't have the same physiology as chinstrap penguins and we don't know if sleep works for us in the same way. way.
Rather, the study shows that "a sleep pattern that could be bad for us - I mean, that could cause a pathology that we can't sustain - could be an adaptation for other animals and help them survive," he added.
Libourel said there is still a "big gap" in our understanding of the role of sleep and the impact of human disturbances and climate change on sleep and animal life. "I think that's why it's important to study sleep. Sleep plays a central role in animal behavior," he added.
In a perspective published in Science, Christian Harding, a postdoctoral researcher at the University of California, San Diego, and Vladyslav Vyazovskiy, a professor of sleep physiology at the University of Oxford, wrote that the study "not only challenges the current understanding of how sleep architecture is regulated, but also the extent to which it can be changed before the benefits of sleep are lost."
They added that climate change and human activity are putting "increasing pressure on natural habitats," which "affects the quantity and quality of sleep in wildlife."
They said sleep studies such as this "are the best way to take advantage of the opportunity to study sleep in wild animals, free from human influence, while it is still possible."
Editor's Note: Call to Earth is a CNN editorial series reporting on the environmental challenges facing our planet, along with the solutions. Rolex's Perpetual Planet initiative partners with CNN to raise awareness and education around important sustainability issues and inspire positive action.
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