It is the mammal that sleeps the least in the world. On average, the northern elephant seal (Mirounga angustirostris) sleeps only two hours a day. This is the result given by a Californian study conducted on several individuals off the coast of the United States. To sleep, elephant seals dive to a depth varying between 90 and 300 meters. According to several scientists, the location and the short duration of sleep would allow these marine animals to increase their chances of survival against predators.