A 4-second power nap? These penguin parents survive on ‘microsleeps.’

Sleep-deprived human parents know the value of a quick nap, but it turns out chinstrap penguins have us all beat.

When nesting, these Antarctic birds take four-second-long “microsleeps,” a strategy that allows parents to keep constant watch over vulnerable eggs and chicks, all while racking up 11 hours of total sleep a day, according to a new study.

“They always seem to be in a microsleep state,” says study co-leader Paul-Antoine Libourel, a research biologist at the Neuroscience Research Center in Lyon, France.

The results, published this week in Science, are the latest in a series of new findings that show a wide diversity in animal sleep strategies. In April 2023, researchers found that elephant seals take short naps as they dive beneath the waves. Bottlenose dolphins sleep with half their brain at a time, leaving the other hemisphere awake and alert. So do frigate birds. And during mating season, pectoral sandpipers opt for sex over sleep. (See 24 endearing photos of animals sleeping.)

“We don’t know why some animals can display two hours of sleep a day like the elephant and others require 20 hours of sleep,” Libourel says.

Sleep of the penguins

It’s hard to sleep in a colony of nesting chinstrap penguins. The Antarctic summer sun provides 24/7 daylight, illuminating the hustle and bustle of thousands of honking, noisy birds. And then there’s the eye-watering smell of ammonia mixed with rotting fish and penguin guano. (Learn how chinstrap penguin populations have fallen dramatically on this Antarctic island.)

“It made me dizzy,” says co-study leader Won Young Lee, a researcher at the Korea Polar Research Institute.

Like other penguins, chinstrap parents take turns guarding the nest. While one bird protects the chicks—usually two—the partner forages at sea. Then the penguins trade places. For two months between egg laying and fledging, it’s a series of nonstop demands. (Read more about the secrets of sleep.)

“Penguins can swim 120 kilometers a day while foraging. Not even Michael Phelps can do that. And if you can sleep while you’re on autopilot coming back, that would be really good,” says P. Dee Boersma, a penguin expert at the University of Washington and National Geographic Explorer.

To study how penguins manage to accomplish all this and get the necessary sleep, Lee and his team first stuck biologgers, small battery-powered devices, to the backs of 14 nesting penguins of both sexes. This device functions like a smartwatch, measuring physical activity, pulse, and the ocean depths of foraging birds. 

Next, the team humanely captured each of the penguins, anesthetizing them to attach the devices and temporarily implant electrodes into their skull to measure brain activity. When an animal is awake, the brain constantly buzzes with activity. During sleep, however, brain waves slow down and stretch out.

When Lee started reviewing the data, he was surprised to discover the birds—which were released after the study—slept in four-second intervals throughout the day and night while caring for their egg or chick.

Short-term strategy for tired parents?

Anyone who has ever nodded off briefly while on the subway or watching TV has experienced a microsleep, says Chiara Cirelli, a neuroscientist at the University of Wisconsin who wasn’t involved in the study.

In both humans and penguins, microsleeps occur during times of fatigue and exhaustion, yet nesting chinstrap penguins seem to have a near-exclusive reliance on it, Cirelli says. Studying sleep in natural environments is difficult, so “the simple fact that they were able to record data in these conditions is incredible.”

While the data is convincing, Cirelli notes that the researchers only studied the penguins during nesting periods, making it impossible to tell if the birds microsleep when they’re not parenting. (Learn more about the possible origins of sleep.)

The other challenge is understanding how microsleep impacts the brains and bodies of the penguins. Sleep deprivation in humans causes a range of health problems, and it’s not clear whether penguins experience this, too.

Since chinstraps sleep in slightly longer stretches while diving for food and after they return to land, Libourel says that microsleep may be just a short-term coping strategy for tired moms and dads.