Why Do Dogs Wag Their Tails?

It is generally believed that a dog wags its tail when it is happy, or in any case excited and cheerful. However, this is not entirely true, the wagging of the tail by dogs is the equivalent of facial expressions in humans, ie not only communicate happiness or joy but express a range of emotions and feelings . This characteristic developed because of the way dogs live and hunt in their natural state, that is, in the pack. Just as humans, dogs are highly sociable and group animals, so over the millennia different characteristics emerged to maximize group communication. For example, a dog with a taut and tense tail that at the same time emits a sharp moan, is indicating a danger close to the members of his pack. However, the communication system of the canines is very complex, and several parts of the body are involved, which are used simultaneously. This complexity very regularly leads to humans confusing their signals and several accidents, which otherwise could have have been avoided, occur because of a communication problem. It is precisely because of this that wagging the tail does not always mean joy or happiness, in fact if the dog does "pushing" its ears back and showing its teeth it is most likely to attack us.

And why the wagging of the tail is reserved for the most important communications
The intention of mating, joy and attack are all emotions that communicate by wagging the tail and only differ by exerting some variation in the speed of the wiggle, or the position of the ears and snout. Something that certainly leads us to induce the importance that exists in the movement of the tail. Indeed we would not be wrong to think it this way since dogs in their anus have secretory glands which, when stimulated by the rhythmic movement of their tails, release different pheromone signals. Although humans have largely lost our hormonal communication system, in dogs, this type of communication is still the strongest of all. Thus, when they are captured by other members of the pack, they can determine the age, social status, fertility, etc. of the member that issues them.

Note: Hunting dogs are usually cut their tail not only for aesthetics, but to avoid communication during the hunt and thus avoid disobeying the orders of their masters. In fact, in nature, the length of the tail is very related to the dominate character. A wild dog, the longer its tail, will tend to be dominant.
A clear example of this exists in dogs of the Dobermann breed, whose anatomical arrangement of the tail hinders their movement, which is why their communication with other dogs is hampered. For this reason they have always been considered antisocial.

The signs

A slight and slow wiggle of the tail with the ears raised: The dog does not know if the person is friendly or not, so he moves his tail dubiously and remains attentive to respond to any attack. A sudden movement by the person and the reaction of the dog could be violent.

Locate the tail between the legs: Fear, fear of the situation. In addition to protecting the testicles in male dogs this prevents the secretion of pheromones, making detection of the dog more difficult. In a rough way, evolutionarily, the dogs that placed their tail between their legs while escaping from an enemy hunting pack had a greater chance of surviving.

A quick and short wiggle showing the teeth and pushing the ears back: The dog is ready to attack, is convinced that the person or object is not friendly.

Tail tense and standing with hair twitching: Usually when dogs twitch the hair on their back and tail is not a friendly sign, but it is not a sign of attack. It means rather that the dog will not attack, but neither will it leave the territory. The best thing to do in these cases is to retire slowly.

A quick movement of the tail that also moves the back part of the body: Happiness, joy.

Stop the tail and bend the tip slightly to the side of the head: Indicates supremacy, usually the dominant male and female walk in this manner.

Other considerations to keep in mind: As we have mentioned throughout the note, the queue is not the only communication feature. For example, relaxed lips, that is, covering the teeth, signal tranquility in the animal. Stopping ears usually indicate attention or play; however, by pushing them back, minimizing the grip point as much as possible, is a clear warning of attack.