jack Russell terrier dog chasing tail outside wagging tail

Why Do Dogs Have Tails And Why Do They Wag Them?

One of the most distinctive features of a dog is his tail. Dog tails can be long or short, fluffy or silky, curved or straight, thick or thin, etc. But no matter what the tail looks like, the one thing that doesn't change is that dogs have them (yes, even if they're docked).

Tails are direct outgrowths of a dog's spine and are thus made of bones, which are also called vertebrae like the bones in their spine. The number of bones in a tail varies by breed, ranging from five to 23. But none of this explains why dogs have tails in the first place. So we discuss why below, along with why dogs wag their tails:

Why do dogs have tails?

Because dog tails are all different, it's believed that their purpose depends on the breed and what it was bred for. For example, the Golden Retriever has a long, strong tail that helps it steer in the water when retrieving waterfowl and other kill. Greyhounds, on the other hand, have thin and lean tails to help them balance at high speeds. And Huskies have curled, heavily furred tails to provide extra warmth, especially when sleeping as they can cover their faces and noses with their tails.

But beyond their purpose as it relates to breed, all dogs use their tails as tools for communication. They are able to express how they are feeling at that particular moment through their tails. For instance, dogs may hold their tails up high when they are alert, curious and excited. Or they may tuck their tail between their legs when feeling afraid. If they hold their tail out horizontally, in line with their back, it may mean they are relaxed or indifferent. And of course, there's the famous tail wag, which has several meanings that we detail next. 

Why do dogs wag their tails?

It's a misconception that tail wagging automatically means a dog is happy and the question "why do dogs wag their tails" is more complex than you may think. This is because dogs hold their tails at different degrees and wag them at different speeds and to different sides. All of these combine to communicate a wide variety of things.

In addition, the neutral or natural position of a dog's tail depends on the breed. While most dogs have tails that hang by their heels when relaxed, others hold their tails more vertically (like Beagles) or under their bellies (like Greyhounds or Whippets). And others have tails coiled tightly against their bodies (like Pugs and French Bulldogs) that don't really show any kind of wagging. These breeds communicate via other body language like ear position, facial expression, bottom wagging and stance.So to interpret what your dog's tail wag means, you'll need to know what their neutral or natural tail holding position is and go from there.

In the meantime, here are some reasons why your dog may be wagging his or her tail and how you can tell which one they're expressing:

  • Happy - tail is in a neutral or slightly raised position with a healthy wag of broad strokes.
  • Excited - tail is in neutral or slightly raised and fast wagging; the faster the wag, the more excited the dog is.
  • Friendly - tail is in neutral or slightly raised with more freely wagging tail and sometimes a simultaneous hip wiggle.
  • Insecure or tentative - tail is wagging slightly or slowly (Pro Tip: best to remove your dog from the situation, person or animal he or she is insecure or tentative about).
  • Aggressive or feels active threat - tail is vertical with a fast wag.
  • Relaxed or pleased - tail is wagging to the right side of the body.
  • Alert, stressed or anxious - tail is wagging to the left side of the body.

Another reason your dog may be wagging his or her tail has nothing to do with expressing emotions but rather his or her desire to spread their natural scent. Dogs sometimes wag their tails to spread their natural sent from their anal glands. Dominant dogs tend to hold their tail high to release more scent, while submissive dogs hold their tail lower.

Pro Tip: If you notice your dog suddenly stop wagging his or her tail and freeze, it may be a sign that he or she wants to divert a threat without being aggressive. This may occur, for example, when a dog is being petted by strangers and doesn't want to interact with them. 

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