Which animal sleeps the least?

Which animals do not sleep?

Time and again, the dolphin has to serve as a prime example of the sleepless animal. Because, of course: He has to swim to the surface at regular intervals to breathe, and how should he sleep there? “A misunderstanding,” says Vorster: “Sleep often goes hand in hand with physical rest, but not necessarily. Those who sleep can continue to behave stereotypically and do not necessarily have to be motionless. Like sleepwalkers: We wouldn't deny them that they are asleep. And in principle the dolphin does exactly the same thing. «The trick of the marine mammal is the so-called half-side sleep: in the dolphin only one half of the brain sleeps alternately while the other is awake. Half the brain is not enough for creative, intelligent behavior, you need to be alert. But established behavior - like swimming - can be managed well with one half of the brain.

You can not only swim in your sleep, but also fly. Different birds achieve this in different ways. Migratory birds like common swifts can stay in the air for up to 300 days without ever landing. The birds soar thousands of meters and then slide and fall into a deep sleep - for an average of ten seconds. "Like other animals, birds can have very short sleep periods," says Vorster. "Just because it seems incredibly short to us doesn't mean the animals aren't sleeping."

Another animal that is often mentioned that supposedly never sleeps is the bullfrog - and has been doing so since 1967. At that time, a study concluded that bullfrogs were sleepless because they did not react to electric shocks when they were awake or resting, or at least completely different than expected. Five decades after the experiments, however, one has to state that not only the execution of the experiment, but also the interpretation of the results is absolutely questionable. Follow-up experiments have long described related species as deeply asleep, and it is accepted that all vertebrates, including bullfrogs, are fairly certain to sleep.

So there are invertebrates. Insects like bees and flies were clearly shown to be asleep. Also the sleeping habits of more curious invertebrates like the scorpion and the sea snail Aplysia californica are well documented.