By: Caroline Chen

It’s surprising how northern elephant seals still have energy to swim in the sea with 2 hours of sleep a day on average.

Northern elephant seals swim in the sea for months with few brief breaks on the shore.

When they are in the sea, they snooze less than 20 minutes at a time. On average every day, they only get 2 hours of sleep. It puts them in a big rival against African elephants on how much sleep they get every day.

“It’s important to map these extremes of sleep behavior across the animal kingdom,” says Jessica Kendall-Bar. She is an expert at studying marine animals at the University of California, San diego.

Tracking seal sleep

Experts track how much seals move while they are sleeping by using brain-wave readings and motion data.

Matching the seals’ brain-wave readings to their diving motions on this journey showed how northern elephant seals get their sleep on long voyages.