Species throughout nature have engineered a variety of solutions for snoozing
Especially for students, sleep is a vital resource! Getting enough hours per night can be a constant challenge for us, but many species in the animal world have evolved clever ways to squeeze in some sleep.
Many animals, like humans, are monophasic sleepers, which means they sleep for a long time each day, according to National geographic. Other species are polyphasic, sleeping in shorter chunks throughout the day; lions lie down in the shade and average about 18 hours of cat naps every 24 hours.
Many prey animals are too vulnerable to predators when lying down, so they came up with a solution: lock their legs. Thanks to this ability, horses can sleep upright, depending on Smithsonian Magazine. They sleep like this most of the time but will lie down to sleep if they feel safe enough. Predation, along with the time they have to spend looking for food, explains why some herbivores sleep only three hours a day.
Vulnerable marine mammals also have interesting solutions to stay safe while they sleep. Walruses would hook a tusk to an iceberg while they sleep to prevent them from floating, according to the BBC Earth. Sea otters wrap themselves in kelp and hold each other by their paws to avoid straying while they sleep.
Mammals living in the depths of the ocean still need to sleep, but it’s a bit more complicated. Since they have to get up periodically to breathe, most cannot simply fall asleep for hours at a time. Instead, they’re only half asleep…literally!
Dolphins enter unihemispheric sleep, resting only half of their brains at a time and keeping one eye open, according to National Geographic. This way they get the rest they need while swimming, breathing, and staying alert to predators.
Sharks must also balance sleep with breathing. Although sharks don’t have to surface to breathe like mammals, they do have to keep swimming. If water is not constantly passing over their gills, they will not absorb oxygen and will effectively drown. Thus, sharks must sleep while swimming, according to researchers from La Trobe University in Melbourne, Australia.
The ocean poses a big challenge for sleep, but so does the sky. Many birds sleep at night while roosting, but hummingbirds take it to the next level. They have such a high metabolism that they would starve if they slept through the night.
Instead, they slow down their metabolism and go into torpor, according to Science. In this quasi-immobile state, they cool their body temperature and their heart rate can drop below 5% of its normal rate. Torpor is not sleep; it is an extreme form of conservation of energy.
Many animals hibernate, but none except hummingbirds make torpor a daily habit. By falling into torpor each night, hummingbirds retain enough calories to wake up and feed each morning.
However, many migratory birds do not have time to stop and sleep at night. Alpine swifts can fly nonstop for 200 days and sleep on the wing, according to research conducted by the Swiss Ornithological Institute. Frigatebirds, which spend much of their lives at sea, also enter unihemispheric sleep during their flight, according to National Geographic.
Unlike bihemispheric sleep — where both hemispheres of the brain rest — unihemispheric sleepers never enter the REM phase, according to National Geographic. REM stands for rapid eye movement, a special type of sleep that humans and various other species enter during deep sleep.
Humans tend to enter REM sleep about an hour after falling asleep, according to the Sleep Foundation. In REM sleep, muscles are temporarily immobilized, giving the brain time to rest and the body a chance to heal. That’s why you need more sleep when you’re sick or injured. REM sleep is also when the sleeping brain is most active and produces vivid dreams.
Cats and dogs also enter REM sleep and dream, according to National Geographic. If you see his whiskers or paws twitching while he sleeps, or if he makes muffled sounds, he’s most likely dreaming.
There is also recent evidence that other types of animals, such as octopuses and cuttlefish, experience REM sleep and dream, according to American Scientist. Rats reenact parts of their daytime activities in their dreams, just like humans do, according to MIT researchers.
The clever ways pets sleep should remind you of the importance of sleep, especially as you approach your final week. Sleeping all night isn’t as useful as you might think. A lack of sleep significantly impairs cognitive functions such as concentration, learning and memory, according to Harvard Medical School. So study hard during the day and spend a good six to eight hours a night, depending on the CDC recommendation. Sleep is the key to success.