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One Eye Open: Animals' Amazing Sleep Trick
16 Jul
Summary
- Some species sleep with one brain hemisphere active.
- This 'half-brain sleep' aids survival in dangerous environments.
- Dolphins, ducks, crocodiles, seals, and frigate birds use this tactic.
Certain species have evolved a remarkable survival mechanism known as unihemispheric slow-wave sleep, enabling them to rest one side of their brain while the other stays awake. This allows animals to maintain vigilance against predators and environmental hazards, even while sleeping.
Dolphins famously utilize this adaptation to breathe, swim, and stay aware of their surroundings in aquatic environments, preventing drowning. Mallard ducks also employ this strategy, particularly when resting in groups, with outer birds keeping an eye open for threats.
Research on juvenile saltwater crocodiles shows they exhibit half-brain vigilance, especially when potential threats are near. This trait is believed to be an ancient evolutionary characteristic shared across reptiles, birds, and mammals.
Fur seals exhibit varied sleep patterns, relying more on half-brain sleep in water than on land. Frigate birds take this to an extreme, engaging in brief unihemispheric sleep while flying during long ocean journeys, thus maintaining flight performance and alertness.
