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Why do dogs wag their tails?

It’s not just because they are excited … 

You’ve just seen a gorgeous dog out in public, and it’s wagging its tail at you, so it must be friendly, right? Well, a dog wagging its tail doesn’t always mean the canine is friendly. Aggressive dogs can also wag their tails before attacking. So how do we tell the difference between the wags? First, we try to understand why dogs have tails in the first place? 

1. Balance / Movement 

Like many animals with tails, the original more primitive role of the tail was to assist with balance when walking over narrow spaces. Tails also allow dogs to maneuver sharp turns when running at high speeds and act as a rudder when swimming.  

2. To spread their scent/pheromones 

It is common knowledge that dogs like to greet each other by sniffing each other’s backends, but have you ever wondered why?  

It is because of their anal glands, which are small sacs that sit on either side of the anus and release a dog’s natural scent. Dogs have an incredible sense of smell, and this unique scent helps differentiate dogs from one another and is one of the ways they release pheromones into their environment. Some dogs don’t always control when they express this scent, and it has a very unfortunate fishy odor. If you notice your dog’s backend smelling this way, you can give it a gentle clean with a Glandex Petwipe (see below). 

but if it is often happening, it would be a good idea to ask for advice from a vet.  

When a dog wags their tail, it helps to spread this natural scent around. Dogs who are confident and fill the ‘Alpha’ role are more likely to hold their tails high, allowing more scent spread to claim more territory. On the opposite end of the spectrum, submissive dogs will often keep their tails tucked low, minimizing the amount of their scent entering the environment and keeping themselves hidden from potential dangers. 

3. Communication  

So now we know the original dog tail meaning, but since their wild days, dogs have been domesticated and now wag their tails mainly to communicate with humans and other animals. A dog wagging its tail is like the equivalent of a human smiling or frowning. Whether the dog is happy or aggressive while wagging its tail also depends on the position, speed, and direction of wagging. 

Tail Position 

Dog tails come in all shapes and sizes. Some are naturally shorter, and some are naturally curled, and like the shape of the tail, the natural position differs from breed to breed. For example, Greyhounds have very long tails that slightly curl under their bellies, Whippets like to carry their tails low, and Akitas and Pomeranians like to hold their tails up high. With this in mind, whether a tail is held vertically, horizontally, or tucked in can be a helpful insight into the dog’s behavior. 

A tucked or low tail often means the dog feels submissive and fearful. A tail held vertically means the dog is more alert and maybe aggressive. A horizontal or neutral tail can indicate curiosity, where the dog is feeling attentive but calm. 

Tail Stiffness 

The tail’s stiffness can help determine the dog’s emotions in conjunction with its position. A tail is held vertically and is very stiff or rigid, while wagging often indicates aggression. Whereas a tail that is relaxed and wagging demonstrates friendliness.  

Speed of Wagging 

A tail that moves quickly while wagging often means the dog is excited. However, the speed of the tail should always be interpreted together with the tail position, as a fast wagging vertical, stiff tail often demonstrates aggression. In contrast, a slightly raised or neutral tail that is wagging quickly indicates friendliness. An excited dog may also wiggle their backend or hips very quickly at the same time as their tail, as their body is happy and relaxed.  

A tail that moves only slightly while wagging may reflect the dog’s uncertainty and apprehension. A tail held still in the neutral position is often a dog’s way of avoiding confrontation without being outwardly aggressive. They are letting others know they are alert but not excited to be in that situation.  

Direction of Wagging  

Although it can be challenging to determine the direction of a dog’s tail wag, it is believed that whether the tail is moving predominantly left or right can differentiate friendliness from aggression. The left side of the brain controls all movements on the right side of the body and vice versa. So why do dogs wag their tail to the right? If this happens, the left side of the brain is active, and this part of the brain is associated more with positive emotions. So, researchers believe that a tail wag to the right means the dog is happy. Why do dogs wag tails to the left? Well, it’s the opposite. In this case, the right side of the brain is engaged, which is responsible for more negative emotions, such as fear and anxiety, so a dog wagging its tail to the left is often feeling afraid.   

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Some dogs don’t always control when they express this scent, and it has a very unfortunate fishy odor. If you notice your dog’s backend smelling this way, you can give it a gentle clean with a Glandex Petwipe.


With all of this in mind, it is essential to remember that each dog is unique, and each breed of dog has its quirks, so not every canine will obey these guidelines for the tail language. Always interpret a dog’s tail wag with the rest of their body language, and if you have any doubt over the friendliness of a dog, don’t approach them without asking their owners first.