Do Animals Dream? What Cats, Rats, Birds—and Even Fish—Do in Their Sleep

🐱 Cats on the Prowl—Even in Their Sleep

Since the groundbreaking research of sleep pioneer Michel Jouvet in the 1960s, scientists have known that cats don’t just sleep—they live through vivid internal experiences. Jouvet discovered that when the part of the brain responsible for muscle paralysis during REM sleep was disabled in cats, they physically acted out dream-like sequences: stalking, grooming, pouncing, and even guarding imaginary prey.

This suggests their dreams may reflect waking life—especially hunting behaviors—locked behind the normal paralysis of REM sleep.

Philosopher David Peña-Guzmán has argued that such behavior supports the idea that animals “re-experience emotions and imagination,” hinting at a deeper, cognitive dream life for felines.

🐀 Rats Running Mazes—With Eyes Closed

A 2001 MIT study stunned the scientific world by recording rat brain activity while navigating mazes—then finding identical neuron patterns in their hippocampus during REM sleep. These patterns weren’t random; they mirrored visual, auditory, and emotional experiences from their waking trials, often replayed at the same pace as in real life.

These findings point toward a dream-like mental state, where memory consolidation, emotional processing, and perhaps even problem-solving take place. Rats may not just be dreaming—they might be rehearsing.

🎶 Birds That Sing in Their Sleep

Zebra finches—and many other songbirds—have been found to replay their learned melodies during sleep. Even more astonishing: some birds chirp softly while dreaming, subtly experimenting with new variations of their daytime songs.

Their sleep isn’t passive. It’s practice.

This neural reactivation was one of the first major clues that non-mammals might also experience REM-like sleep. Sleep, in these feathered creatures, could play a key role in learning, creativity, and adaptation—just like in humans.

🐟 Do Fish Dream? The Origins of REM Go Deep

Even zebrafish—tiny aquatic vertebrates—show evidence of REM-like sleep. They exhibit phases of reduced muscle tone, twitching, and erratic heart rhythms. According to Stanford neuroscientist Philippe Mourrain, this could point to REM sleep having emerged 450 million years ago, long before animals ever set foot on land.

If REM in humans aids memory, creativity, and emotional regulation, similar functions may exist even in fish brains—hinting at an evolutionary continuity of dreaming across all vertebrates.

What Does This All Mean?

The idea that only humans dream is quickly being dismantled. From cats and rats to finches and fish, animals show neurological patterns and behaviors that echo our own nightly adventures.

Whether it’s to remember, rehearse, or reimagine their lives, it appears animals too may enter rich, internal worlds when they sleep.