by The art of falling asleep appears to have been mastered by chinstrap penguins, who take more than 10,000 naps a day, with each nap lasting an average of four seconds, according to a new study.
The animals accumulate about 11 hours of sleep daily using this strategy, challenging a pattern seen in humans that fragmentation is detrimental to sleep quality.
“Microsleeps” or “micronaps” (second-long interruptions of wakefulness that include eye closure and sleep-related brain activity) occur in humans who haven’t gotten enough sleep, according to the study published in the journal. Science magazine on Thursday.
However, falling asleep can be inappropriate and even dangerous in certain environments, such as when driving a car, and it is not clear whether they are long enough to provide any of the benefits of sleep.
600 microsleeps per hour
To investigate whether microsleeping may provide some sleep function and be a useful sleep method in ecological circumstances that require constant vigilance, researchers from France, South Korea, and Germany studied 14 wild chinstrap penguins that were incubating eggs in an exposed colony. to a predatory bird, the brown skua, on King George Island, Antarctica, in December 2019.
During incubation, when skuas are known to feed on penguin eggs, one parent penguin is forced to continually protect the eggs or chicks while its partner is away foraging for food for several days, according to the study. study. They must also defend their nest from intruding penguins and at the same time need to sleep.
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 videos and direct observations.
They observed that the penguins in the colony performed more than 600 episodes of microsleep per hour.
The study authors said that “thousands of microsleeps lasting only 4 (seconds) are unprecedented, even among penguins.”
A small study in 1984 found that captive little penguins placed in metabolic chambers exhibited a state called “quiet wakefulness,” which resembles the microsleep of chinstrap penguins. However, these sleep episodes lasted much longer, 42 seconds on average.
A 1986 study found that captive, non-breeding emperor penguins had fragmented sleep called “drowsiness,” which also resembles the microsleep pattern of breeding chinstrap penguins. However, emperor penguins only spent up to 14% of their time in that state.
In this study, 75% of sleep among chinstrap penguins occurred in episodes lasting less than 10 seconds, according to study co-author and sleep ecophysiologist Paul-Antoine Libourel, who leads and manages projects as part of the sleep team. from the Lyon Neuroscience Research Center. .
“This is not unique in the entire animal kingdom. There are other animals that sleep quite fragmented or in very short periods of sleep. But, as far as we know, they were not able to maintain such extreme fragmentation of sleep for 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 through these brief periods of sleep the penguins were able to “sleep and remain alert” while incubating.
The researchers observed that even after the penguins swapped partners to forage at sea, they slept in the same pattern upon returning to shore.
However, sleep bouts would last longer during the first few hours back on land, indicating that the penguins needed to recover from sleep loss at sea, where they spend a lot of time actively awake doing activities such as diving.
The researchers also compared the sleep of those nesting in the center of the colony with that of those nesting at the border, who are more exposed to predatory skuas and therefore must remain more alert.
Those nesting on the border slept more deeply and slept less and longer than those in the center of the colony, which, according to Libourel, “was quite unexpected” and “the opposite” of what they thought they would find.
He attributed this to a “noisy and disruptive environment” in the center of the colony because many penguins move around, and those heading towards the sea pass by the nests of incubating penguins, making it a difficult environment. for sleeping. Aggression between penguins and other interactions was also added to this.
Despite not directly measuring the restorative value of microsleep, the researchers deduced that “the chinstrap penguins’ heavy investment in microsleep” and “their ability to reproduce successfully, despite sleeping in this highly fragmented manner,” suggests that “microsleep can satisfy at least some of the restorative functions of sleep.”
They concluded that other animals might also have “the flexibility to divide sleep into short or long periods, depending on their ecological demands for vigilance.”
An ‘adaptation’ for survival
Libourel said that they still do not know how physiologically these penguins are able to sleep in this way and warned that sleeping in short periods is not advisable for humans, since we do not have the same physiology as chinstrap penguins and we do not know if sleep works. the same way for us.
Rather, the study shows that “some sleep pattern that could be bad for us – that is, it could induce some pathology that we cannot bear – for other animals, could be an adaptation 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 is central to animal behavior,” she 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 “calls into question not only current understanding.” “It’s not about how sleep architecture is regulated, but also to what extent it can be altered before the benefits of sleep are lost.”
They added that climate change and human activity “are putting increasing pressure on natural habitats,” which are “affecting the quantity and quality of sleep of wild animals.”
They said sleep studies like this “are the best way to take advantage of opportunities 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 committed to reporting on the environmental challenges facing our planet, along with the solutions. Rolex’s Perpetual Planet initiative has partnered with CNN to raise awareness and education on key sustainability issues and inspire positive action.
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