By: Elliott Chu

Jessica Kendall-Bar and her team at the University of California San Diego study Marine Animals studied elephant seals’ sleep time. They attached special equipment to the seal’s brain to identify brains waves, measuring when they are asleep. Their studies revealed that elephant seals only sleep for two hours a day.

The monitor also revealed that they dive 60 to 100 meters below the surface. Then they relax into a glide. As the seals start to doze off, they stay upright for several minutes. But then, they slip into a stage of rest known as REM sleep. During this time, their body becomes paralyzed. It flips upside down and spins toward the ocean floor. The seals drift this deep because it’s far below the waters where the killer whales and sharks find food.

However, when the seals come on shore to mate and molt, they doze off for more than 11 hours a day. “What the seals are doing at the beach might be something like what we do when we sleep in on the weekend,” says Niels Rattenborg, a researcher working with Kendall-Bar.

The team also wanted to find out if other animals had the same characteristic as the elephant seals. They found a similar sleep pattern in great frigate birds. The team made an extraordinary discovery: the birds can sleep while flying. They also discovered that most marine animals sleep with half of their brain off and half of their brain on at a time. This can help them recognize dangerous predators. But the elephant seals sleep with their whole brain, so that makes them vulnerable. Diving deep into the ocean is what helps keep them from being eaten. This is key for the elephant seal to have a deep 20-minute sleep.

Source:

https://scripps.ucsd.edu/news/elephant-seals-drift-sleep-while-diving-far-below-ocean-surface