MBut why are they called elephant seals? Because the scientific name of Mirunga Wasn’t Darwin satisfied? Because, with a weight of about 2 tons, the male crushes, by far, all the other sharks? Because “dominants” develop a stump-shaped nose? Since friday april 21st and article Published in the journal sciencea new answer enriches the catalog: because, with two hours of sleep each night, during the seven months he spends at sea, the northern elephant seal (Mirounga angustirostris) It joins the African elephant at number one on the list of the smallest sleepers.
To this result, a team from the University of California, Santa Cruz (UCSC) owes the development of a revolutionary sensor. It was invented by Alexei Vyssotski, of the University of Zurich (Switzerland), to record the brain waves of birds, and has been adapted to the marine world by Jessica Kendall-Bar. Thanks to a neoprene cap and gold detectors, the UCLA researcher was able to monitor the sleep of thirteen individuals, five in the laboratory and eight in the natural environment, at California’s Año Nuevo Reservation.
Les résultats l’ont stupéfiée: alors that, pendant les cinq mois de la periode de reproduction qu’il passe à terre, l’animal dort dix heures per day, sa durée de sommeil quotidien plonge à deux heures le reste de l’année , In the water. And also : “He reaches them with a short nap of about ten minutes, during his half-hour immersion on the ocean floor.”says Jessica Kendall Barr. Because in the deep sea, up to 2000 meters deep, the animal finds food and security. On the contrary, the two minutes he spends on the surface between two dives puts him at the mercy of killer whales and great white sharks.
Napoleon’s nap
By analyzing the recordings, the researchers observed both the slower waves of deep sleep and the faster waves of REM sleep. exactly like us. In animals, however, they note that the duration of the second is particularly long (up to 25% of the total, versus less than 10% in most species). Above all, thanks to the accompanying measurement of the animals’ movements, also carried out by the sensors, they were able to follow the physical behavior of the animals in these two cases. In deep sleep, its head stops swimming and develops in a normal position, lower abdomen, according to a somewhat downward sloping trajectory. But when he transitions into REM sleep, he loses control of his body, rolls over, belly up, and tumbling down.
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