“Because they are constantly watching their environment” , confirms Jerome Siegel, a neuroscientist at the University of California, US. The sleep of whales, shared by other marine mammals such as dolphins, is said to be “monogamous”: brain recordings have shown that one hemisphere of the brain is at rest, traversed by slow waves, while the other remains alert, with fast waves. The two parts of the whale’s brain alternate between resting and waking phases during each sleep period: it is enough to allow them to stay not far from the surface with the help of small tail beats, and thus breathing. In these animals, breathing is not reflex. “So the whales float to the surface of water when they are at rest, that they only have to open the vent to take a breath of air” Describe the specialist.

Studies of cetaceans in captivity revealed that they slept in shifts of less than an hour, about ten times a day, vertically or horizontally depending on the species. “Noticeable Babies do not sleep at all during the first month of their lives, and neither do their mothers. Jerome Siegel points out. By continuing to move, the young are less vulnerable to predators and keep their body temperature stable, until they have enough insulating fat.

According to Science & Vie No. 1252