The Reason Why Your Dog Wags Its Tail While Sleeping

Unlike daytime tail-wagging, dogs wag their tails while they are sleeping for reasons other than to communicate emotions. Learn the differences between the sleep cycles of humans and dogs, and how a dog's tail wagging may be a sign of the depth and quality of their slumber.

The Reason Why Your Dog Wags Its Tail While Sleeping

Unlike daytime tail-wagging, dogs wag their tails while they are sleeping for reasons other than to communicate emotions. Learn the differences between the sleep cycles of humans and dogs, and how a dog's tail wagging may be a sign of the depth and quality of their slumber.

During sleep, dogs sometimes wag their tails

Photo by Irina on Unsplash

Many dog owners are aware that, like people, dogs experience a variety of emotions. Among the emotions that our canine friends experience are joy, fear, rage, sadness, anxiety, and even love, as well as anticipation, surprise, jealousy, and loneliness. Because they are unable to verbally express their emotions, dogs typically use their tails to do so.

But why does a dog's tail wag while it's sleeping? Does it mean that he is communicating happiness? It may surprise you to learn that this behavior happens for a very different reason, one that has nothing to do with communication. Let's look at what happens to our pets while they are sleeping in order to solve the puzzle of why your dog is wagging its tail at night.

Deep Sleep in Dogs

Dogs and other animals experience multiple sleep cycles, just like people do, according to the American Kennel Club. They have times when they are awake, and then REM and non-REM sleep come after.

Using specialized tools, scientists can monitor these cycles and the corresponding brain activity in dogs. They discovered that the most memorable and vivid dreams occur during REM sleep, which is thought to play a role in why some bodily movements, such as tail-wagging, occur.

What Happens in REM sleep

The interesting thing about REM sleep is that it causes slightly different bodily reactions in people than it does in other animals. We can learn more about why dogs wag their tails while they sleep if we examine the differences between REM sleep in humans and dogs in more detail.

REM Sleep in Humans

About 90 minutes after you lay down to sleep, your body enters REM sleep. As the night wears on, REM sleep lengthens. These are the characteristics of REM sleep in humans:

  • Your body and mind are stimulated.
  • Your breathing accelerates and becomes erratic.
  • You dream because your brain is working.
  • Your eyes flit from side to side.
  • You are unable to act out your dreams because of how relaxed and immobile your body becomes.
  • Your body's temperature regulation is less precise.

REM Sleep in Dogs

Scientists have managed to gather information about canine sleep patterns through clinical observations. They found that as a dog falls asleep, his breathing becomes deeper and more regular. After about 20 minutes of slumber while in REM sleep, dreams usually begin for the average dog. During this stage of heightened mental activity, the following may occur:

  • Your dog may whine, breathe quickly, wag his tail, or move his legs.
  • The dog may breathe shallowly and erratically while dreaming, and its muscles may jerk.
  • A dog's eyes move and dart around behind his eyelids, as though watching something.

During REM sleep, it is very common for a dog to exhibit twitching, tail wagging, leg kicks, and soft barks or grunts. These actions signify that your dog is sleeping soundly and deeply. Both younger and older dogs tend to move more frequently while they sleep.

Dogs reach REM sleep, just as humans do

Photo by BRUNO EMMANUELLE on Unsplash

When Dogs Wag Their Tails While They Sleep, Are They Content?

Dogs are known to wag their tails when they are happy while they are awake. However, when they are sleeping and wagging their tails, dogs are not necessarily experiencing the emotion of happiness.

When dogs wag their tails in their sleep, pet owners often assume that their dog is having a wonderful dream about chasing rabbits or running after a ball. In contrast, when their dogs whine or thrash around, some owners become startled and worry that they may be experiencing a disturbing dream.

The truth is that a dog may be wagging its tail while sleeping but also be experiencing a bad dream. Thankfully, because most canine dreams are not nightmares, VCA Animal Hospital provides assurance that dog owners needn't be concerned about their dog's nighttime antics. If your dog whimpers or shakes his tail while he is sleeping, it is a perfectly natural reaction for any dog during his sleep cycle.

Most doggy dreams are happy ones

Photo by Lisa Fotios

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Final Thoughts

Dogs sometimes wag their tails while they are in deep sleep, either because they are having an enjoyable dream or because they are having a nightmare. Either way, muscle twitching is known to be more frequent in REM sleep than in non-REM sleep and usually becomes more distinguishable as sleep progresses.

If your dog appears to be having a distressing dream, you can gently wake them up, or you can simply leave them to continue having a deep sleep. But even when your pet is asleep, it is always prudent to keep an eye out for their behavior in case something else appears to be wrong.

Sources and Further Reading

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2023 Louise Fiolek


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