Northern elephant seals sleep hundreds of meters below the sea surface, away from predators.
Researchers say that the mammals take two hours of "nap-like sleeping dives" every day. The findings of science are disseminated.
A non-invasive stick-on tag was developed by Jessica Kendall-Bar and her colleagues at UC Santa Cruz. This tag can be used to track and watch the brain activity of wild northern elephant seals that live off the coast of California. They went on hunting missions that lasted seven months and covered 6,200 miles, and they managed to find eight different wild species. They monitored the animals' brain activity as well as their heart rates, how they moved, and where their bodies were positioned. A researcher at Oxford University named Ritika Mukherji stated that "We came up with a scientific' signature for sleep' by studying their behavior and physiology for many years."
When they were deeper than 984 feet, seals would become sleepy and drop in what are called "sleep spirals" for a period of twenty minutes. "They look like falling leaves," Ms. Mukherji added. According to the primary researcher from UC Santa Cruz, Professor Terrie Williams, who was interviewed by BBC News, said, "I find it amazing that any mammal would fall asleep while floating hundreds of meters below the surface of the water."
"This is a deep sleep, the kind that leaves people unable to move and causes them to snore. Even when the seals' lungs are completely empty, their brains are able to force them to wake awake. Imagine you've fallen asleep at the bottom of a pool and you wake up there. That is rather unsettling. The "nap maps" that they created for seals imply that the locations where seals sleep may be just as essential as the locations where they hunt. According to Ms. Mukherji, "It shows us what their world looks like and helps us understand what they're doing and when they're doing it, so that we know how to stay out of their way."