Dolphins: The Insomniac Mammal

Have you ever wished you could only let half your brain sleep so the other half could finish a long day’s work? Unfortunately, as a human, you don’t have that option. But if you were a dolphin, you’d be doing it every day of your life.

Sleep With One Eye Open - Literally

We’ve all heard the phrase “sleep with one eye open.” People say it when they want to suggest that someone could be in danger. It’s not just an expression for dolphins, though; they actually do it.

The two halves of a dolphin’s brain work independently of each other, so one side can go to sleep while the other stays awake. This serves two functions. One, presumably, is so the dolphin can look out for threats from various predators without losing any shut-eye. The other is to make sure the dolphin keeps breathing.

Dolphins move to the surface to get air 2-3 times each minute. If they went into a deep sleep, they wouldn’t do this and would eventually die. Instead, because one side of the brain is always awake, the dolphin always gets enough air.

During each sleep cycle, one side gets its sleep, typically about eight hours. Meanwhile, the other side is taking care of the usual surfacing and breathing activities. After the sleeping side wakes, the dolphin can either stay completely awake or let the other side gets its rest while the rested side takes over the breathing.

Unlike the fish you might see at an El Paso aquarium, which can fall asleep in dark rooms, the dolphins in the water are always resting, and yet at the same time they’re always awake. Makes you a little jealous, doesn’t it?

(Non-) Sleeping Baby Dolphins

It’s hard to imagine a baby not sleeping for long periods of time. That’s what makes baby dolphins so unusual, especially among mammals. Where most young need far more sleep than their adult counterparts, baby dolphins don’t get any sleep at all until they’re 4-5 months old. Scientists don’t know why this happens, but it makes the adult’s sleep patterns seem a bit less strange.

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