If you are a pet owner, you have probably wondered why your pet sleeps so much. Humans need between 5 and 9 hours of sleep on average, but some animals can sleep as much as 20 hours per day!
Animals sleep to repair damage to skin and muscle, aid in digestion, and maintain good health. Animals that don’t sleep well can put on weight and find it harder to fight infections and diseases. A study has proved that insomnia in animals can be hereditary, leading to future generations living shorter lives and threatening the species’ future.
Why is it that some animals need so much sleep? How do they differ from us in their sleeping patterns, and how can a lack of sleep affect animal behavior?
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Why Sleep Is Important To Animals
Whether it is in short naps or long periods, sleep is vital to maintaining good health. During rest, an animal’s body will continue with essential functions such as digestion, repairing damage to tissues like skin or muscle, and other necessary actions.
Pregnant animals may sleep more often due to the physical toll exerted by their body as the unborn babies develop. As they grow, they require more nutrients, which can be exhausting for the mother, causing her to sleep for more extended periods.
Young animals need more sleep than adults because they go through periods of rapid growth, which expends a great deal of energy. Typically, infant animals will sleep for a few hours, then wake to feed by their parents before going back to sleep. As animals age, they require less sleep and will start to travel away from the nest or den.
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Animals That Sleep For Long Periods
North America’s longest sleeper is the Virginia opossum. These small mammals spend roughly 75% of 24 hours sleeping, approximately 18 hours. Opossums are nocturnal, so all of their sleeping occurs during daylight hours. They may wake during this time and even move to a different den, usually a hollow log or tree trunk. Some opossums also use below-ground shelters such as shallow holes, but none that are too deep or elaborate.
Humans are coming in a close second to the opossum—specifically, human babies. As infants, we sleep as much as 16 hours, usually in cycles of 2 to 3 hours between feeds. As we age, we require less sleep. Toddlers aged 1-2 will sleep on average 13 hours out of 24, and aged 3-5 approximately 11 hours.
After the toddler stage, we develop a regular sleep pattern during the night, with most children no longer needing naps during the day. Adults require between 5 and 9 hours of sleep each night, depending on their activity levels and overall health.
Adult squirrels have a similar sleep requirement to newborn humans, sleeping 16-18 out of 24 hours. Squirrels are diurnal, meaning they are active during the day and sleep during the night. They spend some of their sleep time in a light nap and the darkest night hours in a deeper sleep.
Squirrels require so much sleep because they have a very high activity level. They spend their days traveling around their foraging range in search of food. Some food will be eaten, but most food is taken to a cache which the squirrel hides for use during winter when food is hard to find.
Squirrels will also have more than one cache, so they do a lot of traveling during the day. Mothers will also have to make frequent trips back to the nest to nurse their pups, so they will sleep more during this time.
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A pet for many, ferrets spends approximately 60% of their day sleeping. In one day, they will sleep for around 14 hours. They will sleep for 5-6 hours, then have an “awake” period where they relieve themselves, play and eat. This is typically an hour or two.
Ferrets are crepuscular and most active at sunrise and sunset. Ferrets require a lot of sleep because they are very busy, alert animals. A playing Ferret can be challenging to track because they move so quickly, climbing up furniture and running through toy tunnels.
Bottlenose dolphins are commonly spotted off the shores of North America. Their sleeping pattern is unique. Dolphins can put half of their brain to sleep while the other half remains active. This means dolphins can rest while still reacting to their environment and moving to the surface to breathe.
Male dolphins travel in pairs. When they nap, they swim side by side. Females and calves travel in pods of several individuals. Calves will sleep while swimming in the wake of their mother as this means they expend less energy.
Dolphins will switch off one-half of their brain for around 2 hours, then switch to rest on the opposite side. Most of this sleeping is done at night, with bottlenose dolphins sleeping approximately 10 hours every day.
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What Happens If An Animal Doesn’t Get Enough Sleep?
According to scientific observations, some animals, such as bees, do not need to catch up on missed sleep. This means a bee will not sleep longer if rest is missed earlier in the day, but it may sleep deeper, although this is almost impossible to measure.
Most animals, however, do suffer apparent side effects from a lack of sleep. The first sign of poor sleep in animals is a lack of energy and frequent yawning. Sleep allows the body to rest. A lack of sleep means the body has not had adequate time to recoup the energy stores and relax the muscles.
Poor sleep also makes an animal more susceptible to illness. The immune system cannot fight infection effectively if the animal has not had enough sleep. Fighting an illness or healing wounds requires a lot of energy, so this process is more complicated if the body has not rested enough.
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Another common side effect of sleep deprivation is weight change. If poor sleep is just a temporary occurrence, an animal will gain weight. This is due to the reaction that happens within the body. During poor sleep, the brain triggers the release of cortisol – a stress hormone. This hormone causes the body to conserve energy by retaining fat.
In the long term, sleep deprivation can be fatal. The brain cannot function on fractured sleep, and infant animals are more at risk than adults. Prolonged insomnia or interrupted sleep can increase the risk of heart disease, leading to heart attacks or other similar events. This is due to the rise in a protein known as C-reactive protein.
The level of this protein increases if an animal does not get enough sleep. C-reactive protein can cause an increase in inflammation, damaging the heart’s blood vessels.
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Causes of Insomnia In Animals
The most common cause of insomnia is illness. An animal feeling ill or in pain will sleep less as their illness makes them vulnerable to predators. Unfortunately, their lack of sleep makes them less able to react to a threat, so they would still be at risk of predation.
Stress is another key cause of insomnia. Animals, especially wild animals, do not cope well with stress. As the hormone cortisol increases, an animal will find difficulty maintaining its regular sleeping pattern.
Insomnia can also be a genetic disorder. A study conducted in 2009 conclusively proved that sleep could be genetic. They took a group of fruit flies that demonstrated reduced sleep and bred them over 60 generations. These subsequent generations slept approximately 60 minutes per day compared with the 800 minutes expected of their species.
These flies that showed difficulty sleeping and maintaining balance were shorter-lived than the original generation. They were also hyperresponsive to their environment and showed increased cholesterol and free fatty acids.
This study showed that insomnia could be a genetic condition and that animals can pass on their insomnia to future generations. This can gradually weaken the health of the species as future generations live shorter lives and are generally poorer in health and cognitive ability.
References
Cespedes, Y. (2016, July 7). Why Do Cats Sleep So Much? Retrieved from PETMD: https://www.petmd.com/cat/behavior/evr_ct_why_do_cats_sleep_so_much
Chudler, D. (1991). How Much Do Animals Sleep? Retrieved from Washington Faculty: https://faculty.washington.edu/chudler/chasleep.html
Hogenboom, M. (2016, January 21). Why Humans Need Less Sleep Than Any Other Primate. Retrieved from BBC: http://www.bbc.com/earth/story/20160121-the-strangest-thing-about-human-sleep-is-that-we-need-so-little?referer=https%3A%2F%2Fwww.bing.com%2F
Meadows, A. (2021, March 26). Why Do Some Animals Sleep Standing Up? Retrieved from sleep.org: https://www.sleep.org/why-animals-sleep-standing-up/
O’Connell, L. (2011, October 30). Who Needs Sleep Anyway? Retrieved from askabiologist: https://askabiologist.asu.edu/plosable/who-needs-sleep-anyway
Seugnet, L., Suzuki, Y., Thimgan, M., Donlea, J., Gimbel, S. I., Gottschalk, L., . . . Shaw, P. J. (2009). Identifying Sleep Regulatory Genes Using a Drosophila Model of Insomnia. Journal of Neuroscience, 7148-7157.
Stallings, M. (2021, February 25). Animals That Need Hardly Any Sleep. Retrieved from sleep.org: https://www.sleep.org/animals-that-sleep-the-least
Bryan Harding is a member of the American Society of Mammalogists and a member of the American Birding Association. Bryan is especially fond of mammals and has studied and worked with them around the world. Bryan serves as owner, writer, and publisher of North American Nature.