Do Animals Dream? The Science of Animal Sleep & Dreams

Overview

The question "do animals dream?" has fascinated scientists for decades. The answer, based on over 50 years of peer-reviewed research, is almost certainly yes—at least for mammals, birds, and possibly even some invertebrates like octopuses and spiders.

This guide compiles the scientific evidence on animal dreaming, from Michel Jouvet's groundbreaking 1959 cat experiments to the 2022 discovery of REM-like sleep in jumping spiders.

What you'll learn:

• The landmark studies proving animals experience REM sleep
• What different species appear to dream about
• Which animals dream the most (and which don't dream at all)
• The evolutionary purpose of animal dreams

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The Science: How We Know Animals Dream

What Is REM Sleep?

REM (Rapid Eye Movement) sleep is the sleep stage most associated with vivid dreaming in humans. During REM:

• Eyes move rapidly behind closed lids
• Brain activity resembles wakefulness on EEG readings
• Muscles become temporarily paralyzed (atonia) to prevent acting out dreams
• Heart rate and breathing become irregular

The presence of REM sleep in animals—combined with brain activity patterns matching waking experiences—provides strong evidence that animals dream.

The Discovery of REM Sleep in Animals

Shortly after researchers identified REM sleep in humans in the 1950s, scientists began studying it in animals. The findings were remarkable:

Almost all mammals and birds studied exhibit REM sleep, including:

• Dogs, cats, and most household pets
• Rats, mice, and other rodents
• Primates (apes, monkeys)
• Elephants, horses, and cattle
• Birds from finches to eagles
• Platypuses and echidnas

Even some reptiles show REM-like brain activity, though research is ongoing.

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Landmark Studies on Animal Dreaming

Michel Jouvet's Cat Experiments (1959)

The Study: French neuroscientist Michel Jouvet conducted groundbreaking research on REM sleep in cats at the University of Lyon.

The Method: Jouvet discovered that during REM sleep, a structure in the brainstem (the pons) normally paralyzes the body to prevent movement. When he surgically disabled this mechanism in cats, something remarkable happened.

The Results:

"The sleeping cats raised their heads, suggesting they were watching unseen objects; arched their backs; and appeared to stalk prey and get in fights." — National Geographic

The cats, while still electrically asleep according to brain recordings, acted out complex hunting behaviors—stalking, pouncing, and fighting invisible prey.

The Significance: This was the first direct evidence that animals experience dreams with content related to their waking activities. Jouvet's work established the field of REM sleep research and earned him recognition as the "father of modern sleep research."

Citation: The mysteries of sleep and waking unveiled by Michel Jouvet - PMC, 2018

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MIT Rat Maze Study (2001)

The Study: Matthew Wilson and Kenway Louie at MIT's Picower Center for Learning and Memory conducted one of the most cited studies on animal dreaming.

The Method: Researchers implanted electrodes in rats' hippocampi (the brain region involved in memory) and recorded neural firing patterns while rats ran through mazes. They then recorded the same neurons during REM sleep.

The Results:

"Of the 45 rat dreams recorded by Wilson, 20 contained an exact replica of the maze they had run earlier that day. During REM sleep, we could literally see these rat brains relive minutes of their previous experience." — MIT News

The brain patterns were so similar that researchers could identify which specific part of the maze the rat was "dreaming" about at any given moment.

The Significance: This study provided the first evidence that:

1. Animals have complex dreams with specific content
2. Dreams replay and consolidate waking experiences
3. Dream content can be objectively measured and decoded

Citation: Temporally Structured Replay of Awake Hippocampal Ensemble Activity during Rapid Eye Movement Sleep - Neuron, 2001

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Zebra Finch Song Rehearsal (2000)

The Study: Daniel Margoliash and colleagues at the University of Chicago studied how young zebra finches learn their songs.

The Method: Researchers recorded neural activity in the birds' song-production brain regions (the robust nucleus of the arcopallium, or RA) during both singing and sleeping.

The Results:

"From our data we suspect the songbird dreams of singing. The zebra finch appears to store the neuronal firing pattern of song production during the day and reads it out at night, rehearsing the song and, perhaps, improvising variations." — Dr. Daniel Margoliash

The birds' vocal cords even vibrate during sleep—they're essentially "silent singing" without pushing enough air to make sound.

The Significance: This research showed that:

• Dreams may serve a learning and practice function
• Animals can rehearse and improve skills during sleep
• The findings may apply to human language acquisition

Citation: Singing in Their Sleep - University of Chicago Medicine, 2000

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Do Dogs Dream?

Short answer: Yes, almost certainly.

The Evidence

Dogs share the same sleep architecture as humans, cycling through stages including REM sleep. Research shows:

• Dogs spend 12% of sleep in REM (compared to 20-25% for humans)
• Brain wave patterns during dog REM match those of sleeping humans
• The pons functions the same way, preventing dogs from acting out dreams

In 1977, scientists recorded the electrical activity of six dogs' brains for 24 hours and found they spent 44% of their time alert, 21% drowsy, and 12% in REM sleep (Physiological Behavior, 1977).

What Do Dogs Dream About?

Research takes advantage of the same approach Jouvet used with cats. When scientists deactivated the pons in dogs:

"The dreams seem to be extensions of the dog's in-bred behavior. Pointers point at dream birds, and Dobermans bark at dream burglars." — Dr. Stanley Coren, Psychology Today

Dogs likely dream about:

• Chasing squirrels or balls
• Playing with their owners
• Eating food
• Other dogs and social interactions
• Breed-specific activities (herding, retrieving, guarding)

Dream Frequency by Dog Size

Interestingly, smaller dogs dream more frequently than larger dogs:

Dog Size	Sleep Cycle Length	Dream Frequency
Small dogs (Chihuahua)	~12 minutes	New dream every 10 minutes
Medium dogs	~20-30 minutes	Several dreams per night
Large dogs (Great Dane)	~45 minutes	Fewer but longer dreams (10+ minutes each)

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Do Cats Dream?

Short answer: Yes, definitively proven by research.

Cats spend approximately 200 minutes per day in REM sleep—more than most mammals. Michel Jouvet's 1959 experiments remain the strongest evidence that cats dream:

When REM atonia was disabled, sleeping cats would:

• Raise their heads and track invisible objects
• Arch their backs in aggressive postures
• Appear to stalk and pounce on prey
• Engage in fighting behaviors

This suggests cats dream about their primary instincts: hunting, stalking, and defending territory.

Signs Your Cat Is Dreaming

• Whisker twitching
• Paw movements (kneading or "running")
• Tail flicking
• Soft vocalizations (chirps, meows)
• Rapid eye movement visible under closed lids

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Surprising Animals That Dream

Octopuses: Color-Changing Dreams

A 2021 study published in iScience revealed that octopuses experience two alternating sleep states remarkably similar to mammalian sleep patterns.

Key Findings:

• Quiet sleep: Octopuses are pale with little movement
• Active sleep: Dramatic color and texture changes for ~40 seconds

"For around 40 seconds, they dramatically change their color and their skin texture. Their eyes are also moving. All of this happens very conspicuously." — Sylvia Medeiros, Brain Institute of Federal University of Rio Grande do Norte

The sleep cycle repeats every 30-40 minutes, with the active phase showing all the hallmarks of REM-like dreaming.

Why This Matters: Octopuses are separated from mammals by over 500 million years of evolution. If both independently developed REM-like sleep, this suggests dreaming serves a fundamental biological purpose for complex nervous systems.

Citation: Octopuses have two alternating sleep states - iScience, 2021

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Jumping Spiders: The First Invertebrate REM

A 2022 study from the University of Konstanz in Germany made a startling discovery: jumping spiders appear to experience REM sleep.

The Discovery:

Researcher Daniela Rößler noticed that juvenile jumping spiders (which have translucent exoskeletons) would hang from silk threads at night with curled legs—and occasionally twitch. Looking closer, she observed:

• Retinal movements lasting ~77 seconds on average
• Episodes occurring every 20 minutes, increasing throughout the night
• Leg twitching and uncurling during these periods

The Significance:

"The study is believed to be the first time REM sleep-like behavior has been documented in a terrestrial invertebrate." — National Geographic

Do Spiders Actually Dream? The researcher remains cautious: "It's beautiful to think about it that way, that these spiders hang there and they have a visual scene of catching a fly or trying to get a mate. It's quite cute, but probably is going to be very different [from human dreams]."

Citation: Regularly occurring bouts of retinal movements suggest an REM sleep-like state in jumping spiders - PNAS, 2022

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Platypus: The Champion Dreamer

The platypus has more REM sleep than any other mammal studied—over 8 hours per day, compared to about 2 hours for humans.

Key Statistics:

• 60.1% of platypus sleep is REM (vs. ~20-25% for humans)
• 8+ hours of daily REM sleep
• They twitch their bills and heads vigorously during REM

This amount of REM sleep is greater than recorded in any other animal. However, platypus REM sleep has some unique characteristics—the EEG remains high-voltage rather than showing the low-voltage pattern typical of other mammals.

Citation: Sleep in the Platypus - PMC, 1999

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Animals That Don't Dream (Or Dream Very Little)

Dolphins and Whales

Dolphins and whales present a unique case: they have minimal REM sleep despite being highly intelligent.

Why Cetaceans Don't Dream Much:

These animals practice unihemispheric sleep—sleeping with one brain hemisphere at a time while the other stays awake. This allows them to:

• Continue swimming
• Rise to the surface to breathe
• Watch for predators

"Sleep in cetaceans is most often unihemispheric, which means that it produces slow waves in one cerebral hemisphere, while the other shows rapid waves typical of wakefulness." — PMC Research

Key Statistics:

• Episodes of unihemispheric sleep last an average of 42 minutes
• Each hemisphere gets 5-12 sleep episodes per day
• The eye opposite the sleeping hemisphere is usually closed 89% of the time

This represents the lowest amount of REM sleep among mammals, challenging assumptions that REM/dreaming is essential for learning and memory (dolphins are exceptional learners).

Citation: Cetacean sleep: An unusual form of mammalian sleep - PMC, 2022

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Fish

Fish do not have REM sleep as mammals do, so they likely don't dream in the way we understand it. However:

• Zebrafish show distinct sleep states with measurable brain activity changes
• Some fish enter a restful state with reduced response to stimuli
• Research is ongoing into whether fish experience any form of sleep-related neural processing

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Why Do Animals Dream?

Scientists propose several theories for why dreaming evolved across so many species:

1. Memory Consolidation

The MIT rat study strongly supports this theory. During sleep, the brain replays and strengthens memories from the day. This helps animals:

• Learn and remember important locations (food sources, dangers)
• Consolidate motor skills
• Process social information

2. Threat Rehearsal

Dreams may allow animals to practice responses to dangers without real-world consequences. This could explain why:

• Cats dream of hunting and fighting
• Dogs dream of chasing and protecting
• Many animal dreams involve action and movement

3. Neural Development and Maintenance

REM sleep is most abundant in young animals and may play a role in brain development. This could explain why:

• Infants (human and animal) spend far more time in REM sleep
• REM sleep decreases with age across species
• The platypus's primitive brain requires more REM processing

4. Skill Practice

The zebra finch research suggests dreams allow animals to rehearse and improve skills. Birds literally practice their songs during sleep, sometimes with variations.

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Comparison Table: Animal Sleep and Dreaming

Animal	Has REM Sleep	Likely Dreams	Daily REM	Key Research
Dogs	Yes	Yes	~1-2 hours	Breed-specific dream behaviors
Cats	Yes	Yes (proven)	~3+ hours	Jouvet 1959 hunting study
Rats	Yes	Yes (proven)	~2 hours	MIT 2001 maze replay
Platypus	Yes	Unknown	8+ hours	Most REM of any mammal
Zebra Finch	Yes	Yes (proven)	Variable	Song rehearsal research
Octopus	REM-like	Probable	Brief episodes	2021 color change study
Jumping Spider	REM-like	Possible	Brief episodes	2022 retinal movement study
Dolphins	Minimal	Unlikely	Nearly zero	Unihemispheric sleep
Fish	No	No	None	Different sleep architecture

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How to Tell If Your Pet Is Dreaming

Dogs

• Paw twitching or "running" movements
• Whimpering, growling, or barking (often soft)
• Rapid eye movement visible under closed lids
• Irregular breathing
• Dreams typically begin 20 minutes into sleep

Cats

• Whisker twitching
• Tail movements
• Soft chirping or chattering
• Paw kneading motions
• May occur every 25-30 minutes during sleep

Should You Wake a Dreaming Pet?

Generally, no. Dreams and REM sleep serve important functions for memory and brain health. Let sleeping pets lie—literally.

Exception: If a pet appears to be having a nightmare (prolonged distress vocalizations, thrashing), you can gently call their name rather than touching them, as startled animals may bite.

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Frequently Asked Questions

Can animals have nightmares?

Research suggests yes. Dogs sometimes whimper, growl, or show signs of distress during sleep. Given that dreams appear to replay waking experiences, negative experiences (trauma, fear) likely replay as well. Studies show that traumatized animals may have more disturbed sleep patterns.

Do animals know they're dreaming?

Probably not. Lucid dreaming—awareness that you're dreaming—requires metacognitive abilities that most animals likely lack. However, this remains an open research question.

Do elephants dream?

Yes, elephants experience REM sleep, though less than smaller mammals. Wild elephants sleep only about 2 hours per night (in short bursts), with REM occurring only every few days. Captive elephants with safer sleep conditions show more regular REM patterns.

Do birds dream of flying?

Possibly, though research focuses more on songbirds rehearsing songs. Given that dreams appear to replay important waking activities, it's reasonable to hypothesize that flight-focused birds may dream of flying.

Why does my dog chase things in their sleep?

Your dog is likely dreaming about chasing—squirrels, balls, other dogs, or anything they pursued while awake. The pons prevents them from actually running, but some motor signals leak through as twitching legs.

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Research Bibliography

1. Michel Jouvet Cat Studies (1959)

• Authors: Michel Jouvet, François Michel
• Institution: University of Lyon, France
• Finding: Cats with disabled REM atonia act out hunting behaviors during sleep
• URL: PMC Article
• Significance: First evidence of dream content in animals

2. MIT Rat Maze Replay Study (2001)

• Authors: Matthew A. Wilson, Kenway Louie
• Journal: Neuron
• Finding: Rats replay maze experiences during REM sleep with identifiable specificity
• URL: Cell.com
• Significance: Proved dreams contain specific experiential content

3. Zebra Finch Song Rehearsal (2000)

• Authors: Daniel Margoliash et al.
• Institution: University of Chicago
• Finding: Birds replay and practice songs during sleep
• URL: UChicago Medicine
• Significance: Dreams may serve learning and skill development

4. Octopus Sleep States (2021)

• Authors: Sidarta Ribeiro, Sylvia Medeiros
• Journal: iScience
• Finding: Octopuses have alternating active/quiet sleep with color changes
• URL: EurekAlert
• Significance: REM-like sleep in invertebrates suggests convergent evolution

5. Jumping Spider REM Study (2022)

• Authors: Daniela C. Rößler et al.
• Journal: PNAS
• Finding: Spiders show REM-like retinal movements and body twitching
• URL: PNAS
• Significance: First terrestrial invertebrate with documented REM-like state

6. Platypus REM Sleep (1999)

• Authors: Jerome M. Siegel et al.
• Journal: Neuroscience
• Finding: Platypuses have 8+ hours of daily REM—more than any mammal
• URL: PMC
• Significance: Extreme REM sleep in primitive mammal

7. Cetacean Unihemispheric Sleep (2022)

• Authors: Various researchers
• Journal: Sleep Medicine Reviews
• Finding: Dolphins sleep one hemisphere at a time with minimal REM
• URL: PMC
• Significance: Demonstrates REM is not universal for learning

8. Dog Sleep Patterns (1977)

• Journal: Physiological Behavior
• Finding: Dogs spend 12% of sleep in REM with human-like patterns
• URL: AKC Reference
• Significance: Confirms dogs have dream-capable sleep architecture

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Conclusion

Over 50 years of scientific research provides compelling evidence that many animals dream. From Michel Jouvet's cats stalking invisible prey to MIT's rats replaying maze routes to octopuses changing color during active sleep, the evidence spans species separated by hundreds of millions of years of evolution.

Key takeaways:

• Most mammals and birds experience REM sleep and likely dream
• Dreams appear to replay waking experiences—mazes for rats, songs for birds, hunting for cats
• Some invertebrates (octopuses, spiders) show REM-like states
• Not all animals dream—dolphins and whales have minimal REM due to their need for continuous consciousness
• Dream function likely includes memory consolidation, threat rehearsal, and skill practice

The next time your dog twitches in their sleep or your cat's whiskers flutter, science suggests they're experiencing their own rich dream world—one shaped by their instincts, experiences, and daily adventures.

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Related Resources

On Oneironauts:

• Why Do We Dream? 7 Scientific Theories Explained
• What Are Dreams? A Complete Guide
• Lucid Dreaming Statistics: 50+ Research-Backed Facts
• Sleep 101: Understanding Sleep Cycles

External Research:

• Do Animals Dream? - Britannica
• National Geographic: Animal Sleep
• MIT Sleep Research