Why Do Dogs Wag Their Tails?

why do dogs wag their tails

It’s heartwarming to see your dog wagging his tail. But it doesn’t always mean he’s happy. Have you ever stopped to ask why your dog wags his tail at different times?  

It’s more than just force of habit. Dogs wag their tails to communicate complex emotions … from happiness to anxiety. 

Why Do Dogs Wag Their Tails? The 7 Most Common Reasons

As humans, we’re used to using words, facial expressions, and gestures  to communicate our emotions. But for your dog, wagging his tail is a primary way to express himself. 

As you may have noticed, though, not all tail wags mean the same thing. They have different causes and can sometimes signal completely different emotions. To help you recognize what your dog’s tail wags mean, here are a few of the most common reasons dogs wag their tails. 

1. Evolution

Even though dogs’ tails have evolved to help them communicate, it didn’t start out that way. In fact, dogs’ tails helped them balance. This is how many wild animals use their tails today. The tail acts as a balancing weight when making a sharp turn or climbing a steep hill. 

As dogs evolved, they needed the tail less and less for balance, and it started to play a greater role in communication. For dogs, using their tails to communicate starts as early as one month of age, when puppies start communicating with their mother and littermates. A tail wag might signal a request for milk from mom, or signal littermates that there’s too much roughhousing going on. 

2. Scent

Another primary way for dogs to communicate and interpret the world is through scent and smell. Every dog has their own unique scent, and the scent itself is a form of communication between dogs. When a dog wags his tail, it spreads this scent from its anal glands. This also means that a dog who’s holding his tail between his legs doesn’t want to spread his scent at all. This may communicate that he’s nervous or trying to stay unnoticed. 

3. Happiness

Ever wonder: “why do dogs wag their tails when they're happy?” It all comes down to how your dog communicates friendliness and happiness. 

A full, whole-body wag or wiggle is the most common tail wag in dogs, and it helps them express happiness, not just to humans but to other dogs. 

Another indicator that you’re getting a happiness wag from your dog is that he’s holding his tail high while wagging. 

4. Aggressiveness

Not all wags are happy wags. If your dog’s tail is stiff and rigid, with a slow-moving tip, it can indicate aggression. This wag even has its own name: “flagging.”

A flagging wag may be accompanied by other signs of aggression, like a still body, a low growl, or an arched back. 

5. Alertness

Certain tail movements may not express an emotion like happiness or aggression, but may just be a signal that your dog saw, heard, or smelled something that caught his interest. A tall, stiff, tail tends to indicate this alertness. It’s a sign that your dog has noticed something, and may soon run after it. 

6. Nervousness

A tucked tail usually indicates nervousness, even if it’s wagging quickly. Tucking the tail isn’t always a sign of uneasiness or anxiety though. Some dogs tuck their tails to look smaller, and communicate to other dogs that they aren’t a threat. 

7. Greeting

Lastly, tail wagging can also be similar to a smile, nod, or verbal greeting in humans. It may be your dog’s way of saying hello to you or other dogs. Dogs' eyes are particularly sensitive to movement, so a wagging tail is a bit like waving hello from a distance. 

Why Do Dogs Wag Their Tails When Sleeping? 

Have you noticed your dog wagging his tail while sleeping? This is actually normal during REM sleep, and can indicate that your dog is getting really good, deep sleep. Moving during sleep is more common in elderly dogs and puppies, and may take the form of tail wagging, twitching, kicking, or grunting softly. 

Why Do Dogs Wag Their Tails When They Are In Trouble? 

If your dog wags his tail when you’re scolding him, it’s likely the nervous or submissive wag described above, where your dog tucks his tail between his legs. If your dog is in trouble, this wag can indicate submission and fear. If your dog’s tail isn’t tucked while you’re scolding him, it’s possible he’s doing a normal wag in an effort to calm you or himself down. 

RELATED: How To Calm Dog Anxiety Naturally

Bottom Line

Most tail wags are a simple way for your dog to express he’s happy or alert. But different kinds of wags can also indicate other emotion, like nervousness or aggression. Pay attention to a dog’s tail position if you want to clue into the emotions of your dog or another dog.

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