by Breeding chinstrap penguins seem to have mastered the art of nodding, taking more than 10,000 naps a day, with each nap lasting an average of four seconds, according to a new study.
The animals accumulate around 11 hours of sleep every day using this strategy, challenging a pattern observed in humans that fragmentation is detrimental to sleep quality.
“Microsleeps” or “micronaps” – seconds-long interruptions of wakefulness, including eye closure and sleep-related brain activity – occur in people who have not had enough sleep, according to the study published in the journal Science on Thursday .
However, nodding 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 hour microsleeps
To investigate whether microsleeps can provide any sleep functions and be a useful sleep method in ecological situations that require constant vigilance, researchers in France, South Korea and Germany studied 14 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 skuas are known to prey on penguin eggs, one penguin parent is forced to continuously protect the eggs or chicks while their partner is away foraging for several days, according to the study. They also need to protect their nest site from intruding penguins, while trying to sleep at the same time.
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 were engaged in more than 600 one-hour microsleep bouts.
The authors of the study said that “thousands of microsleeps lasting only 4 (seconds) are unprecedented, even among penguins.”
A small study from 1984 found that small captive penguins placed in metabolic chambers exhibited a state called “Woeful Quietness,” which is similar to the microsleep of chin-strap penguins. However, these sleep bouts lasted much longer at an average of 42 seconds.
A 1986 study found that non-breeding emperor penguins in captivity had a fragmented sleep called “sleep,” which is also similar to the micro-sleep pattern of hatchling chinstrap penguins. However, the emperor penguins only spent up to 14% of the time in that state.
In this study, 75% of sleep among chinstrap penguins was in episodes lasting less than 10 seconds, according to study coauthor and sleep ecologist Paul-Antoine Libourel, who pilots and manages projects as part of the sleep team at the Research Center Neurology de Lyon. .
“This is not unique across the animal kingdom. There are (are) other animals that sleep rather fragmented or in very short bursts of sleep. But, as far as we know, they were not able to maintain such a great fragmentation of sleep of days and hours, day and night, and continuously (like the penguins). And this is what was very interesting in our results,” Liborel told CNN on Friday.
He added that the penguins could “sleep and stay alert” while incubating through these short bursts of sleep.
The researchers noticed that even after the penguins swapped with their partners to hunt for food at sea, they slept in the same pattern when they returned to shore.
However, the sleep cycles would last longer during their first hour back on land, indicating that the penguins needed to recover from losing sleep at sea, where they spend enough time awake actively doing activities such as diving.
The researchers also compared the sleep of those nesting in the center of the colony with those on the border, which are more exposed to predatory scats and therefore need to remain more alert.
Those nesting at the border slept deeper and had longer and shorter sleep cycles than those in the center of the colony, which Liburel said was “quite unexpected” and “behind” what they thought they found.
This led to a “disturbed acoustic environment” in the middle of the colony due to many penguins moving around, and those going to sea passing the nests of the penguins hatching, making it a difficult environment to sleep in. Aggression among penguins and other interactions were also said to contribute to this.
Although they did not directly measure the restorative value of the microsleeps, the researchers suggested that “the great investment of chin penguins in microsleep,” and “their ability to breed successfully, despite sleeping in this way is very fragmented ,” suggests that “microsleeps can be performed at least. some of the restorative functions of sleep.”
They concluded that other animals “may have the flexibility to divide sleep into short or long bouts, depending on their ecological demands for vigilance.”
‘adapt’ to survive
Libourel said that they still do not know how physiologically these penguins are able to sleep in this way and warned that it is not advisable for humans to sleep in short bursts, since we do not have the same physiology as the penguins chinstrap and we do not know which sleep. functions in the same way for us.
Rather, the study shows that “certain sleep patterns that might be bad for us—I mean, might foster some pathology that we can’t foster—for other animals, which be an adaptation and help them survive,” he said.
Liborel said there is still a “big gap” in our understanding of the role of sleep, and the impact of human disturbance 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,” he said.
In a perspective published in Science, Christian Harding, a postdoctoral scholar 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 calls into question the current understanding. 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 amount and quality of sleep in wild animals.”
They said sleep studies like this one “are the best way to seize opportunities to study sleep in wild animals that are free from human influence while still being feasible.”
Editor’s Note: Call to Earth is a CNN editorial series dedicated to reporting on the environmental challenges facing our planet, along with the solutions. Rolex’s Perpetual Planet initiative is partnering with CNN to promote awareness and education around key sustainability issues and to encourage positive action.
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