A tail tucked under is an indication of fear.
A wagging tail is often mistaken for a sign of friendliness, but this could be a serious mistake. Just because a dog is wagging his tail doesn’t mean that he is social or that he wants you to pet him.
A tail that is very low and wagging rapidly can indicate stress or fear, and it can also indicate excitement.
A tail that is held very high and wagging indicates high arousal.
The dog could be excited to greet you, or he could be getting agitated and contemplating lunging or even biting.
In general, a mid-level or low, swishy tail wag is a sign of happiness or friendliness.
Some dogs get so happy and excited that their tails go around in big circles.
