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Every year, along Antarctica’s rocky, icefree coast, millions of chinstrap penguins (Pygoscelis antarcticus) form breeding colonies chaotic, noisy and, yes, smelly and lay eggs in November that hatch in late December and January.
During these months, protecting the nest is a serious matter for these penguins as brown gulls lie in wait. Therefore, falling asleep while working can be disastrous for the eggs and of course for the chicks. But this species, as scientists announced this Thursday (30), has developed an ingenious way to get enough sleep without compromising alertness.
Researchers have documented very strange sleep behavior. Instead of sleeping for long periods of time, chinstrap penguins sleep thousands of times a day only for about four seconds each time and meet their sleep needs cumulatively, for a total of about 11 hours a day.
“They show an unexpected adaptation of sleep, a compromise between the need to sleep and the need to be awake,” said PaulAntoine Libourel of the Neuroscience Research Center in Lyon, France, lead author of the study published in the journal Science.
“This has not been documented before,” said behavioral ecologist and study coauthor Won Young Lee of the South Korean Polar Research Institute in the city of Incheon.
In December 2019, data was collected from 14 penguins incubating eggs in a colony of about 3,000 breeding pairs on King George Island in Antarctica. The researchers measured electrical activity in the brain evidence of sleep activity using electroencephalography.
In addition, they filmed the birds and used other biorecording devices such as GPS monitors and accelerometers to track their location and body movements.
While chinstrap penguins guard their nests, they sleep an average of 10,000 to 15,000 seconds per day breaks in alertness for a few seconds, with eyes closed and sleeprelated brain activity. Sleep occurs while standing or lying down.
Sleep is a precious commodity because of its restorative value. Microsleep can be dangerous for people for example when driving. But not for chinstrap penguins.
“Penguins show no obvious negative consequences of sleep fragmentation,” Libourel said. “Because birds can reproduce and forage efficiently, we believe that the function of sleep can be fulfilled even when sleep is disrupted in this way.”
Lee said other animals may use similar sleep strategies, although this has not yet been documented.
Chinstrap penguins, one of the most common penguins in Antarctica, are so named because of the black band of feathers under their chin. Adults are between 70 and 80 cm tall and weigh 3 to 6 kg.
They usually stay with the same breeding partner year after year in a kind of marriage. The females lay two eggs in a circular nest made of stones, and the young hatch about 37 days later. During this time, males and females share parental responsibilities, with one constantly guarding the eggs or chicks while the other forages for food in the sea for several days.
Seagulls also hunt penguin eggs during this time, especially on the outskirts of a colony. Chinstrap penguins also have to defend their nests from other penguins invading the crowded and noisy colony.
“It’s an incredible landscape, constantly changing, not so cold, with an average temperature of around 1°C. But sometimes very windy and with snowfall,” said Libourel.
“As a field biologist, I have been observing penguins since 2014. The penguin colony is located near the coast. It stinks quite a bit because of the penguin poop. Plus, the penguin calls are very loud,” Lee added.