For some animals, rest comes in fragments.

Sleep is often assumed to be universal, yet across the animal kingdom it varies dramatically. Some species survive with almost no true sleep, relying instead on brief pauses, partial brain shutdowns, or constant low alert states. Scientists studying animals in oceans, skies, and harsh terrestrial environments have documented patterns shaped by predation risk, migration demands, and physiology. The stakes are high because losing awareness can mean death. These animals challenge long held assumptions about why sleep exists at all and how little of it life can endure.



