If you've ever seen elephant seals(象海豹) lying on a beach, you might think all they do is sleep. But now scientists have discovered that when elephant seals are in the ocean, they hardly sleep at all. They just sleep for about two hours a day.
Even though elephant seals are large animals, they have to be careful in the ocean. Near the surface(水面), predators like sharks and orca s are a danger. So elephant seals spend most of their time diving(潜水) deep underwater, looking for food. Usually, they will dive for about 30 minutes, then come up for air for just a couple of minutes before diving again.
Scientists have wondered how elephant seals can sleep while they're at sea, since they are almost diving all the time. Animals like dolphins and sea lions have a special way. One half of their brain can sleep, while the other stays awake. But elephant seals are like humans- both halves of the brain need to go to sleep at the same time. So how do they sleep?
To find out, a scientist named Jessica Kendall- Bar did a research. She created a special cap that could record the elephant seals' brain activity. The cap also collected information on the elephant seals' heart rates, how their bodies were moving, and how deep they were. Dr. Kendall- Bar and her team put the caps on thirteen young female elephant seals.
The scientists learned that elephant seals steep in short times while they are diving. They only sleep for about 10 minutes at a time. They wake up in time to go up for more air. The scientists found that elephant seals only sleep for about two hours a day when they're in the ocean. That means that the rest they get once they return to land is very important, which helps them have energy again. Back on land they sleep for about 10.8 hours a day
The researchers hope that their work will help to protect the places where elephant seals sleep when they're on land.
