Report by Prashasti Kulkarni
The 20 ft. (almost as tall as 3 ½ adult humans) mammals known scientifically as Mirounga angustirostris, commonly called elephant seals, have an average lifespan of 9 years (if they’re from the Northern seas) or 20-22 years (if they’re from the Southern seas). They weigh upto 4.5 tonnes and migrate to look for food, spending upto 8 months at sea during the summer. They return to land during the winter to breed. They are carnivorous, meaning they eat mostly living beings such as squid, fish, sting-rays and sharks.
How and when do Elephant Seals sleep?
Since elephant seals spend most of their time at sea searching for food, holding their breath for up to an hour at a time, diving constantly, scientists have always wondered when they get the time to sleep.
In a recent study, scientist Jessica Kendall-Bar created a helmet, which, using a tool called electroencephalogram, could record the brain activity of elephant seals. The scientist and her team tested these helmets on thirteen young female seals to find information ranging from the seals’ heart rates to their sleeping patterns.
Image credit: Annca/Pixabay
This is the information the scientists gathered about their sleeping habits:
- Like humans, the brains of elephant seals are completely shut off when they sleep (animals like dolphins sleep with only half their brain unconscious to allow them to be vigilant, among other benefits).
- While at sea, elephant seals sleep in short periods of time, each period being around 10 minutes. In total, they sleep about 2 hours per day.
- As the seals are starting to sleep (in a stage called SWS or slow-wave sleeping), they can have slight control over their body, sliding down easily. However, when they’re sleeping deeply (in a stage called REM), they lose control and start to fall in a spiral motion. When they wake up, they swim up for air and then continue hunting.
- While on land (mostly during winter time), rest is very important for elephant seals as they don’t get much of it at sea. So during this time, they sleep for over 10 hours per day.
The study was funded by various organizations, including the National Science Foundation, Office of Naval Research and Strategic Environmental Research and Development Program.
Elephant seal image credit: Bryan Hanson/ Pixabay