How Do Animals Sleep?
Discover surprising facts about how animals sleep!
Rest and recovery are the main reasons why we sleep. During sleep, our body relaxes and our brain takes a break, which helps improve our memory. Interestingly, it's not only humans who sleep, but also animals, including reptiles, insects, and fish!
We provide answers to all your questions about sleep in the animal kingdom. You'll also find amazing sleeping facts from the animal kingdom in this article.
Do All Animals Sleep?
The answer is: We don't know yet. There is evidence that animals of most animal classes sleep. But scientists have not yet been able to determine real sleep states in all of them. They have only been able to prove that they go through periods of rest.
Do Mammals Sleep?
Yes, mammals experience similar sleep phases to humans, including REM and non-REM stages.
Do Birds Sleep?
Yes. The sleep of birds is very similar to that of mammals. Just like us humans, they go through REM and non-REM phases. When they're overtired, they sleep longer to recover more.
Do Reptiles Sleep?
It seems surprising, but the sleep of reptiles is also very similar to that of mammals. Although there are differences in brain waves, brain activity also decreases. Bearded dragons have even been shown to have REM sleep. Crocodiles can even sleep with only one side of their brain - similar to sharks and dolphins.
Do Amphibians Sleep?
It's a fact that Amphibians rest, but they don't sleep like people or birds. Their sleep is a mystery. Nobody knows exactly if and how they sleep.
Do Insects and Spiders sleep?
Yes. Scientists already know that bumblebees, bees, butterflies, paper wasps, praying mantises and fruit flies sleep. Spiders even dream.
Do Fish Sleep?
Yes, fish sleep too. Some of them can even dream, for example the zebrafish. It may even suffer from overtiredness if it doesn't get enough sleep.
Do Invertebrates Sleep?
Yes, they can sleep. Octopuses and cuttlefish even dream.
Dreaming
Can animals dream? Yes. Researchers have discovered that all mammals dream - except the echidna. But what about birds? And insects? It has actually been proven that certain species within these animal orders do dream. For example, pigeons, squids, lizards, spiders and zebrafish.
REM Sleep
REM means “Rapid Eye Movement” and describes a state of sleep in which our eyes move back and forth very quickly under our closed eyelids. We experience most dreams in the REM phase.
Sleeping with One Half of the Brain
Some animal species have a special ability. When they're tired, they can “switch off” one side of their brain. Most of these animals are marine mammals. It is crucial for them to stay awake with a part of their brain to prevent drowning yet still be able to come up for air during sleep. Some bird species also have this ability. They need to stay awake because they need to be alert for any potential attackers.
Mammals:
- River
- Dolphin
- Beluga Whale
- Narwhal
- Bottlenose Dolphin
- Sea Lion
- Maned Seal
- Fur Seal
- Manatee
- Pilot Whale
- Porpoise
Birds:
- Swifts
- Blackbird
- Chicken
- Duck
- Peregrine
- Falcon
- House
- Sparrow
Hibernation
Hibernation is different from normal sleep. Biologists aren't sure yet, but they believe that hibernation doesn't provide the same level of rest as real sleep. The Arctic ground squirrel, for example, has been observed to regularly wake up from hibernation, return to its normal body temperature and then it immediately lies dormant to make up for the lost sleep. Then it goes back into hibernation.
Sources:
- "Warming up for sleep? — Ground squirrels sleep during arousals from hibernation" (https://www.sciencedirect.com)
- "Octopus sleep includes a frenzied, colorful, ‘active’ stage" (https://www.sciencenews.org)
