wag their tails! 
The tail is one of the main body of the animal compared with ours. But what we really need? For the dog's tail is the instrument (with sound) most important statement of moods. Normally it wags its tail is interpreted as synonymous with happiness. But not everyone knows that there are various stages of contentment. In the book "The Intelligence of Dogs" author Stanley Coren points out that if we look the dog in different occasions of excitement, we can see that the movement is not always equal to itself: changes the speed and range of motion changes depending on the different levels of arousal and excitement of the plea. When we return home and wag their tails is slower means that the dog is greeting us by "routine", but is happy that he knows something, it happens frequently. But when it wags its tail is more frenetic sound accompanied perhaps by barking and jumping, that indicates an overwhelming joy. Like when we grasp the leash to take him out. Then there is the so-called wagging reassuring: when playing the dog wags its tail in a way that serves to make us understand that everything we do (barks, growls, terminals, ports) will be made for "playful! In short, the dog laughs and smiles the corner! But this part of the body also serves to identify the social status of the animal: as studied by Desmond Morris, the famous ethologist, dogs subjected make a movement of the tail low, wide and relaxed while the dominant dog and aggressive movements are short, dry and high tail. But if we look good, in fact, even the dog wags its tail in a dual master's cnfronti signifiacto: contentment but also in fear towards the pack leader. Have you ever noticed that often the dog comes to meet there to greet you with wagging tail but with the body slightly down to earth? Now you know why! The tail also has another important function in the communication of the dog. Lying just above the anal glands, with its movement or dampens the dog exacerbates the odorous signals especially for sexual purposes. This is why the dominant dog advances with his tail high, making a little 'oblique position called "flag" and wags his tail slowly and stirred with a concentrated, with the bravado of those who are confident and want to disclose its identity by spreading the smell around. The rather subdued, feeling less, it does little and goes low and wagging his tail to tail with a tendency to lean back on the train. In this position the tail covers the anal region and then hide the smell of an individual, as to hide their true identity for fear. The active and passive submission have been clearly defined and described by Marco Poli in his book on "animal ethology Psychology" based on the greater or lesser degree of submission which also takes note of the tail wagging the low and slow active submission and tail between its legs folded back to passive.
So now we will look more important than this lump!
