Elephant Seals Take Power Naps During Deep Ocean Dives
During the many months they spend at sea gorging on fish and squid,
the massive mammals sleep only about two hours a day.
It long seemed as though African elephants were the champions of the all-nighter. They can get by on about two hours of sleep. Other
mammals need much more, like koalas (20 hours) or you (at least seven
plus at least one strong cup of coffee).
But the largest living mammals on land have some competition at sea.
Northern elephant seals are also able to sustain themselves on about
two hours' sleep, according to a study published Thursday in the
journal Science. The study found that Northern elephant seals sleep
far less at sea than they do on land, and the z's they do catch at sea
are caught hundreds of feet below the ocean's surface. The study's
authors believe that sleeping in the deep allows the seals to
power-nap without being eaten by prowling predators.
...
...
"They dive down, stop swimming and begin to glide," Dr. Kendall-Bar
said.
As they go deeper, their brain activity starts to slow.
"Then they transition to REM sleep, where they flip upside down and
spin in a circle, falling like a leaf," she said.
While in rapid eye movement, or REM, sleep, which is the deepest stage
of sleep, the seals stayed upside down, oblivious to their slow
descent.
After sleeping for around 10 minutes, the seals would suddenly wake up
and make their way back to the surface. During these sleep dives, some
seals sank over 1,000 feet, sometimes finding themselves on the
seafloor.
https://www.nytimes.com/2023/04/20/science/elephant-seals-sleep-dive.html?smid=tw-nytimes&smtyp=cur
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