Why Do Dogs Wag Their Tails In Their Sleep?

You’re sat on the sofa enjoying a cup of coffee while your dog snoozes on the rug by your feet. Everything is calm and quiet. You might even be enjoying the smell of your dog sleeping.

But then the silence is broken by a strange noise…

*Thud*… *Thud*… *Thud*…

You look down to see your dog enthusiastically wagging their tail against the floor, despite the fact they still appear to be fast asleep!

You wonder what’s going on! Why would your dog wag their tail in their sleep?

Read on to find out.

The Reason Why Dogs Wag Their Tails In Their Sleep

Here’s the short answer:

The most likely reason why dogs wag their tails in their sleep is that they are dreaming.

However, the longer answer is a bit more complicated:

We don’t actually know for sure that dogs dream, or that wagging their tail in their sleep is always a sign of dreaming.

While it’s easy to see your dog wagging their tail in their sleep (or maybe feel their tail whacking you, if you have one of those dogs that likes to sleep with their bum in your face) and assume they’re having a nice dream, it’s difficult to say this with 100% certainty, because dogs obviously aren’t able to tell us whether or not they dream.

Another complicating factor is that animals sometimes move and make noises in their sleep even when they are not dreaming. For example, humans talk in all stages of their sleep, not just during REM sleep when most dreaming occurs.

The best we can say – based on the fact that dogs enter REM sleep, like humans do – is that it is very likely that dogs dream. And, as it’s likely that they dream, it makes sense that wagging their tail in their sleep is, at least sometimes, an outward sign that they are in the middle of wagging their tail during a dream.

Why Do Dogs Wag Their Tails?

We’ve learned that dogs wagging their tails in their sleep is probably a sign that they’re in the middle of wagging their tail in a dream. But why do dogs wag their tails anyway?

Whether a dog is awake or dreaming, what causes them to wag their tail and what purpose does tail wagging serve?

The answer is that dogs wag their tail to communicate emotions to other dogs and humans around them.

Interestingly, it’s not quite as simple as a wagging tail meaning that a dog is “happy”. In fact, researchers have found that dogs wag their tails more to the right when experiencing a positive emotion, and more to the left when experiencing something negative.

This directional tail wagging sends a message to other dogs. Studies have shown that dogs are more relaxed and willing to approach another dog that is wagging its tail to the right, and will become stressed around a dog that is wagging its tail to the left.

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