5 animals with the most fascinating sleep habits

3 min readNew DelhiJul 15, 2026 05:58 PM IST

Sleep is essential for nearly every living creature, but the way animals get their rest can be wildly different from that of humans. Evolution has equipped different species with remarkable adaptations that allow them to sleep while avoiding predators, survive harsh environments, or continue long migrations. From birds that nap in the sky to turtles that breathe through their rear end during hibernation, these are some of the most fascinating sleep strategies in the animal kingdom.

1. Alpine swifts: Birds that sleep while flying

During their months-long migrations between Europe and Africa, Alpine swifts can remain airborne for extended periods. Research suggests they take brief naps lasting just a few seconds while gliding at high altitudes. This allows them to conserve energy without interrupting their migration. Scientists believe these micro-sleeps are possible because the birds spend much of their time soaring rather than actively flapping, making short bursts of sleep feasible without losing control of flight.

2. Ducks: One half of the brain sleeps at a time

Many duck species have mastered unihemispheric slow-wave sleep, in which one hemisphere sleeps while the other remains awake. The open eye keeps watch for predators while the sleeping half of the brain gets the rest it needs. Ducks positioned on the outer edge of a flock remain more alert than those safely tucked into the middle, showcasing an impressive survival strategy.

3. Sea otters: Sleeping while holding hands

Sea otters often sleep floating on their backs in coastal waters. To keep from drifting apart in strong currents, they often hold paws or wrap themselves in kelp, which acts as a natural anchor. This behaviour helps family groups stay together while they rest and prevents individuals from drifting into dangerous open waters.

4. Sperm whales: Vertical power naps

Sperm whales have one of the most unusual sleeping postures in the animal kingdom. They often sleep almost motionless in an upright, vertical position, with their heads pointing toward the surface. These naps usually last less than 20 minutes and occur close to the water’s surface.

5. Freshwater turtles: The surprising “butt breathing” sleepers

Some freshwater turtles, including Australia’s Fitzroy River turtle and Murray River turtle, spend long periods underwater during winter hibernation. While asleep, they dramatically reduce their metabolism and obtain much of the oxygen they need through cloacal respiration—absorbing oxygen-rich water through specialised sacs connected to the cloaca, an opening at the rear of the body. Although popularly described as “breathing through their bums,” the process is actually a sophisticated adaptation that enables the turtles to remain submerged for weeks or even months without regularly surfacing for air.

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