Where Do Animals Sleep?

Here at Sleepopolis, sleep is our thing. While we normally focus on sleep practices for people, we’re taking a beat to examine what goes on in the rest periods of non-human animals. Like, where do animals sleep? How much sleep do they need? 

To help answer these questions, we spoke with a couple of animal experts who spend a lot of their time training and understanding the animal world. 

Allie Bender, CDBC, CPDT-KA, SBA, founder of Pet Harmony Animal Behavior & Training told us no two species are exactly alike in terms of how animals sleep. In fact, “There’s a lot of variation within each category, even within the same type of animal, in addition to the differences between categories,” she said.  

Joanne Fernandez-Lopez, director of veterinary affairs at ABCs Puppy Zs, agreed, stating that, “All animals have diverse sleep habits and locations that are adapted to their environments and lifestyles.”

Let’s examine how sleeping habits can vary between mammals, amphibians, reptiles, and avians. You might be surprised to learn just how different many of these animals are from one another. 

Long Story Short

• Non-human animals need sleep just like we do, but where, when, and how much they sleep varies significantly.
• Some animals sleep standing up, submerged underwater, while swimming or flying, perched on a tree branch, or even burrowed deep underground.
• An animal’s sleep habits depend on their natural environment and their need for energy conservation, body temperature regulation, and the behaviors of their social groups.

Mammals

When it comes to mammals, many people are best acquainted with their pet dog who sleeps at the foot of their bed, or perhaps their cat, who likes to fall asleep on the kitchen windowsill. As a whole, mammals tend to engage in a variety of sleeping habits, which are influenced by the environment they’re in as well as their metabolic needs and any survival strategies they may need to deploy. 

Most mammals experience two primary sleep phases, including rapid eye moment (REM) and non-REM sleep. (1) This also means they have dreams and other brain processes similar to those we experience when we sleep. How long they sleep and whether their sleep patterns are interrupted depend on several factors, like if they have to be on the lookout for predators or conserve energy. 

Fernandez-Lopez notes that land mammals may sleep in dens, nests, or burrows, while some sleep in trees or even standing up. Marine mammals will sleep in their aquatic environments, sometimes fully submerged. Then you have bats, who are notorious for sleeping upside down in trees or caves. Overall, mammals come with a mix of sleeping habits that largely depend on where they live. 

Here’s a peek into some of the sleeping habits of a few well-known mammals.

Wolves

The wolf pack that may come to mind when envisioning wolves remains intact even when these wild dogs sleep, as group safety is crucial to their survival. You won’t see them out much during the day as they’re usually resting in their den or another location hidden away until it’s time to hunt (in the twilight hours). But even when asleep, wolves rest in short bursts or sleep lightly so they can wake up quickly to the sound of potential predators or prey. 

Dolphins 

Dolphins are among a unique group of animals that exhibit unihemispheric sleep. (2) This means that while one half of their brain is asleep, the other half is awake (like sleeping with one eye open, but literally). This allows dolphins to remain aware of any threats and to continue breathing through their blowholes while they doze. And don’t worry — both sides of the brain get to rest, as they switch back and forth between which one is working. 

Elephants

You might be surprised to hear that elephants typically only sleep for a few hours per day and can go several days without any. While they might catch a few deeper Z’s lying down on the ground, elephants are also known to sleep while standing up. These massive animals need to eat regularly, so their sleep is often interrupted to move around and find food, on top of being aware of any potential threats around them. 

Monkeys

As you might expect, monkeys usually sleep up in the trees where they’re safer from predators on the ground. Like wolves, they tend to sleep in social groups for more protection. Most monkeys sleep for around 8-10 hours per night and are active throughout the day — though they might take an afternoon nap to recharge so they can continue to monkey around. 

Polar Bears

The sleeping habits of a polar bear vary depending on the season. For instance, they enter dormancy in the winter and sleep a lot, which slows their metabolic functions to conserve energy. During this time of year, they dig shallow pits in the snow to help retain body warmth. When it’s not so cold outside, polar bears are more active and sleep less, except after they finish a large meal (like us with Thanksgiving). 

Reptiles

Unlike mammals, birds, and humans, reptiles don’t experience an REM phase during their sleep cycle. (3) Instead, they tend to get more slow-wave sleep, which is a deep sleep needed for muscle repair, immune function, and energy conservation. 

Fernandez-Lopez tells us that reptiles are ectothermic (AKA cold-blooded), which means their surroundings regulate the temperature of their body. She says reptiles often seek warm, safe places to sleep, like in the sun or near a heated rock. Their sleeping habits vary year-round based on the weather and available resources. 

Below are a few of the most common types of reptiles and how they like to sleep. 

Snakes

Snakes are very aware of their surroundings and sensitive to vibrations around them. When they sleep, it’s more like resting, which can be for extended periods after they eat something large. 

You’re most likely to find snakes hidden in rocks, bushes, holes, or other safe places where they can stay out of sight when resting, says Fernandez-Lopez. Interestingly, snakes sleep with their eyes open — which they have to do because they don’t have eyelids. 

Bender reminds us that snakes exist in most parts of the world, so their living environments can include deserts, topical regions, the ocean and other water sources, swamps, temperate forests, and grasslands. Some snakes sleep in burrows underground, while others sleep in the water or even up in trees — further demonstrating the influence of their external environment. 

Crocodiles

Like dolphins, crocodiles keep half of their brain working while they sleep for safety. (4) As they spend most of their time near a body of water, crocodiles tend to sleep in these areas as well. They expend more energy hunting at night and are generally resting during the day to replenish those energy stores. 

Turtles

Turtles generally sleep at night and are awake during the day, but this can change depending on their need for food and environmental factors around them. Fernandez-Lopez says you might find land turtles in shallow burrows or natural shelters, like between rocks or plants, to stay protected while they sleep.

Aquatic species of turtles can stay underwater for hours while asleep, coming up for air every once in a while. For example, red-eared sliders hibernate in the winter, so while they typically sleep underwater or nap while basking in the sun, they will bury themselves in the mud at the bottom of a lake or pond in the winter, says Bender. 

Amphibians

Amphibians are animals that live both in the water and on land, and their sleep habits reflect their environment. They don’t have well-defined sleep stages like mammals do, and their rest is often irregular as they try to stay alert to their surroundings. (5)

Amphibians heavily rely on their environment for body temperature control and hydration. When water is less available, they might rest more or enter torpor, which is a type of hibernation that’s easier for the animal to come out of when needed. (6)

Here’s what you can expect from a few members of the amphibian family.

Frogs

Frogs are nocturnal and sleep during the day, so they have to be strategic about how to avoid predators while staying cool. According to Fernandez-Lopez, “Frogs often sleep half-submerged in the water or hidden in damp vegetation, while some species burrow into mud or soil.”

They can enter a state of torpor — remember, that’s a type of hibernation that’s easier to come out of — during dry or cold conditions, where their activity and metabolic rates slow significantly. However, frogs are still sensitive to changes in their environment when they’re sleeping, and their restfulness is influenced by their need for water (which they absorb through their skin). 

Salamanders

Salamanders generally sleep in protected places that are cool and damp to help hide them from predators and keep them moist. For example, Fernandez-Lopez says, you’re likely to find salamanders under rocks, logs, or in leaf litter near a puddle. They’re more active at night, resting during the day in these more concealed areas.

While salamanders don’t have a well-defined sleep cycle, they enter periods of low activity during the colder months, with some species hibernating during the winter until it’s warm enough for them. Because salamanders are vulnerable to drying out, they usually sleep lightly so they can remain vigilant about changes in their environment.

Toads

Toads are known for having thicker, rougher skin than frogs, which allows them to rest in drier environments. You might find toads lightly sleeping in shady, moist areas like underneath a log or partially buried in the ground, as they sleep during the day and are active in the evening. 

Toads can become more dormant when it gets too cold or dry for them, during which they burrow deep into the ground to save their energy and protect themselves. 

Avians

Avians (birds) live high-energy lifestyles that require constantly staying alert, something that their sleeping habits reflect. Like dolphins and crocodiles, birds can sleep unihemispherically, with half of their brain shut off. So, when you see a bird perched somewhere with one eye open, it may be sleeping. 

Most birds take short naps during the day rather than sleeping for long periods. While many birds go through both REM and non-REM sleep, their REM is shorter than most mammals to allow them to stay alert to threats while resting. (7)

Fernandez-Lopez says that some of our avian friends might fall asleep standing up, perched, floating on water, or even for short periods while they’re in flight (like frigatebirds and common swifts). Overall, how birds sleep can vary widely depending on their environment, activity, and even migration patterns.

Here are some of the sleep habits of various types of birds.

Hummingbirds

Most of us only get to see hummingbirds up close when they suddenly appear at our bird feeder or near the flowers in our yard, mesmerizing us with how fast their wings flap (averaging around 50 to 80 beats per second). (8) And these little birds require adequate rest given all the energy it takes to fly and hover like they do.

“Hummingbirds are pretty cool in that they typically enter torpor nightly, but the duration is dependent on species and individuals,” says Bender. During torpor, their heart rate and metabolism drop so they can survive the night without eating. If this sounds dramatic, remember that hummingbirds are constantly burning energy. They need to eat about half of their body weight in sugar each day. Experts say they could eat up to 48 small meals in just eight hours to keep up. (9)

Hummingbirds often sleep in branches or leaves where they can stay hidden from potential threats. They’re most active during the day, resting at night when it’s cooler.  

Toucans

“Toucans will nest in tree cavities but typically sleep on perches when they’re not nesting,” says Bender. However, she notes that there are over 40 species of toucans, so there could be even further variation between the individual birds. Most toucans will sleep with their beaks tucked under their bodies. 

These birds are diurnal, meaning they are active during the day and sleep at night. Like many other animals, toucans sleep in groups for safety. 

Flamingoes

Flamingos are social sleepers who tend to rest more at nighttime and nap during the day when needed. Fernandez-Lopez says you’re likely to find flamingos asleep while standing on one leg in a body of shallow water, like a lake or lagoon. (10) 

As awkward as it may look, this position actually helps them stay balanced and conserve body heat and energy as they rest. And they’re able to do it because they’re another animal who has mastered unihemispheric sleep.

FAQs

The Last Word From Sleepopolis 

Sleep is a necessity of life for everyone, including non-human animals. As you can see, there’s significant variation in how animals sleep, whether they’re land or marine mammals, amphibians, reptiles, or members of the bird family. Much like us, animals have to adapt to their surroundings, conserve energy when things get tricky, multitask, and recharge after a long day.

Sources

1. Patel AK, Reddy V, Shumway KR, Araujo JF. Physiology, Sleep Stages. In: StatPearls. Treasure Island (FL): StatPearls Publishing; January 26, 2024.
2. Konadhode RR, Pelluru D, Shiromani PJ. Unihemispheric Sleep: An Enigma for Current Models of Sleep-Wake Regulation. Sleep. 2016;39(3):491-494. Published 2016 Mar 1. doi:10.5665/sleep.5508
3. Miyazaki S, Liu CY, Hayashi Y. Sleep in vertebrate and invertebrate animals, and insights into the function and evolution of sleep. Neurosci Res. 2017;118:3-12. doi:10.1016/j.neures.2017.04.017
4. Kelly ML, Peters RA, Tisdale RK, Lesku JA. Unihemispheric sleep in crocodilians?. J Exp Biol. 2015;218(Pt 20):3175-3178. doi:10.1242/jeb.127605
5. Lesku, J. A., Aulsebrook, A. E., Kelly, M. L., & Tisdale, R. K. (2019). Evolution of Sleep and Adaptive Sleeplessness. Handbook of Behavioral Neuroscience, 30, 299-316. https://doi.org/10.1016/B978-0-12-813743-7.00020-7
6. Ambler M, Hitrec T, Pickering A. Turn it off and on again: characteristics and control of torpor. Wellcome Open Res. 2022;6:313. Published 2022 Mar 29. doi:10.12688/wellcomeopenres.17379.2
7. Rattenborg NC, van der Meij J, Beckers GJL, Lesku JA. Local Aspects of Avian Non-REM and REM Sleep. Front Neurosci. 2019;13:567. Published 2019 Jun 5. doi:10.3389/fnins.2019.00567
8. Bartlett P. (2018). Johns Hopkins Medicine. Fueling the Hummingbird’s Extreme Biology. Retrieved from: https://www.hopkinsmedicine.org/news/articles/2018/10/fueling-the-hummingbirds-extreme-biology 
9. Arizona State University. Ask a Biologist: Hummingbirds. Retrieved from: https://askabiologist.asu.edu/hummingbird-foraging 
10. Chang YH, Ting LH. Mechanical evidence that flamingos can support their body on one leg with little active muscular force. Biol Lett. 2017;13(5):20160948. doi:10.1098/rsbl.2016.0948
11. MassWildlife’s Natural Heritage & Endangered Species Program. (n.d.). Mass.gov. Species spotlight: Little brown bat. Retrieved from: https://www.mass.gov/info-details/species-spotlight-little-brown-bat 

Fernandez-Lopez, Joanne. Personal interview. September 5, 2024. 

Bender, Allie. Personal interview. September 5, 2024.