A little carelessness can have serious consequences for chinstrap penguins in Antarctica and sub-Antarctic islands. Birds of prey attacking their nests are a constant danger and even other members of the species sometimes target nest material that has already been collected. Little penguins therefore have no choice but to always be vigilant and never completely lose sight of their surroundings.
An impossible task if the animals slept for several hours at a time. But that’s not the case, says sleep expert Paul-Antoine Libourel of the Lyon Neuroscience Center in France: “Like other bird species, chinstrap penguins have a sleep rhythm characterized by many short recovery phases that are repeatedly interrupted.”
However, the sleeping behavior of penguin species is also special in the animal kingdom. “On average, they only sleep four seconds at a time,” Libourel told science.ORF.at. Their recovery phases are therefore significantly shorter than with other bird species. To get enough rest, chinstrap penguins enter microsleep several hundred times per hour, regardless of the time of day or night. “According to our calculations, they sleep on average more than eleven hours a day.”
Search directly at the breeding site
To collect the necessary data, a research team led by Libourel examined a group of chinstrap penguins in Antarctica. “The population there has the advantage of already being relatively well researched and, above all, of always returning to the same breeding site.” This makes data collection and comparison much easier.
The team outfitted some penguins with implanted sensors and then performed electroencephalographic (EEG) studies, among other things, to document the animals’ brain activity. At the same time, researchers collected video material and data on the penguins’ movements and their breeding and hunting sites. The researchers are currently presenting the results of the study in the journal Science.
“Sleep studies usually take place in the laboratory – but important factors such as environmental influences are always missed. “We also can’t bring the penguins into the lab,” Libourel said. According to the sleep specialist, it was even more important to be able to examine chinstrap penguins in their natural environment – using “minimally invasive methods”.
“Most extreme example” of interrupted sleep
According to the expert, the sleeping behavior of chinstrap penguins is a clear indication that even interrupted sleep guarantees recovery. The effects of microsleep accumulate over time, allowing penguins to be careless for just a few seconds and still gain energy. To date, chinstrap penguins are the “most extreme and vivid example” of this in the animal kingdom, Libourel said.
However, it’s not entirely clear why penguins developed this sleep rhythm. Many factors could be responsible for this, such as the hidden danger of birds of prey. But it’s also possible that they simply can’t sleep anymore because of the penguin group’s often noisy environment. The many different signals from members of the same species and also the imminent danger of nest material being stolen can put animals on constant alert. But the most likely scenario is a combination of several reasons, says Libourel.
Microsleep even while hunting
The researchers also demonstrated that penguins do not regularly nap at the breeding site. According to their own information, they were also able to document for the first time that the animals recovered during the hunt. Total sleep duration is significantly reduced, but penguins sometimes find enough time, even in water, to float briefly and sleep for a few seconds.
Furthermore, the team found no differences in the sleeping behavior of different penguin specimens. There were also few significant differences in the data collected between men and women, which, according to Libourel, is probably due to the fact that both parents are equally responsible for incubating eggs and foraging for food.
According to the expert, the new discoveries serve as a basis for future investigations and could help in the future to understand the exact links between sleep, the environment and the behavior of penguins. As a result, this could also make future measures to protect chinstrap penguins much easier.