Like humans, animals need to sleep for similar reasons including recharging and repairing the body. The amount of sleep they need depends on the species.
So, for instance, a three-toed sloth sleeps about 16 hours a day, the little brown bat almost 20 hours a day, and the giant armadillo sleeps 18 hours, which is too much when compared to African elephants that sleep about 2 hours, and cows and horses 3 to 4 hours a day. Hence, we may conclude that the amount of sleep animals need is far more different from humans, which is 7 to 9 hours a day.
But, there’s also another difference. Namely, animals’ sleep is polyphasic which means that it is divided into several periods of time. On the contrary, humans’ sleep is either monophasic (sleeping once in a 24-hour period) or biphasic (one main sleep and a short nap during the day).
The Comparison between Human and Animal Sleep
REM Sleep in Humans and Animals
During sleep, human bodies go through four stages each characterized by different types of brain activity and physical changes like reduced temperature and heart rate. The fourth stage, also known as rapid-eye-movement (REM) sleep, is the stage characterized with most activity including fluttering eyes, muscle twitching, and waking-like electrical brain patterns, and occurs every 90 to 120 minutes during sleep.
But, not all animals have REM sleep but many terrestrial mammals like primates and certain reptiles and birds go through this stage of sleep. But, the amount of REM sleep depends on the species. For example, elephants don’t experience REM sleep daily, whereas house cats have up to 8 hours of REM sleep a day. On the other hand, scientists haven’t noticed yet any typical REM sleep behavior in whales and dolphins, although whales do experience some muscle twitching.
The Brain in Humans and Animals during Sleep
When sleeping, the entire brain of humans, both the left and the right hemispheres, shows sleeping characteristics. Unlike humans, certain animals only have one brain hemisphere sleep at a time which has been noticed in dolphins. During sleep, one hemisphere of the brain shows sleep characteristics whereas the other portrays characteristics of being awake. Thanks to this phenomenon they are able to swim to the surface to get air while sleeping.
Lack of Sleep in Humans and Animals
You may already be familiar with the fact that humans are extremely likely to experience mood changes, impaired memory, and illness without getting enough sleep. The same risks also apply to many animals, too, like rats for example. To be more precise, when rats are sleep-deprived they lose weight fast and are prone to developing infections. What’s more surprising, rats die after being sleep deprived for a few weeks.
The Connection between Human and Other Primate Sleep
A study shows that humans slept the least with more REM cycles compared to the other 30 types of primates included in the study. That is why human sleep is referred to as being more efficient than the sleep of other primates. And, because of nest building – a clear commonality among primates – it is believed that the last common ancestor between humans and primate animals was a nest builder.
Sleep Disorders in Humans and Animals
Finally, there’s also proof that some sleep disorders are common for both humans and animals. Research conducted on rats, mice, cats, and dogs, shows that several animal species may experience the following sleep disorders: narcolepsy, sleep apnea, insomnia, and restless leg syndrome (RLS).