DOLPHINS SLEEP ONE SIDE AT A TIME

Because they don’t breathe underwater, dolphins have evolved different sleep patterns that take these into account, according to Scientific American. One of their more amazing adaptations is their ability to sleep one side at a time, a sleep pattern called cat-napping. One half of the brain stays awake to maintain lowlevel alertness in case predators or obstacles appear. This side also signals when to rise to the surface -- usually around two hours -- so a sleeping dolphin can take a fresh breath of air, and then the process reverses, letting the active side rest.

They also have different ways of sleeping while swimming. In one of their deeper forms of sleep, dolphins simply float like a log on the water’s surface, which is why it’s called logging. In echelon swimming, young dolphins sleep while towed along in their mother’s slipstream. The mother is also usually asleep during this time -- dolphin mothers don’t stop swimming for several weeks, in fact. Newborn dolphins lack the blubber needed to float easily, so falling asleep will mean that they will sink.