One of the most endearing traits about dogs is their incessant tail wagging. It has come to represent happiness and a joy of life that humans have a hard time understanding. But there is much more to that wagging tail than a mere expression of happiness. Dogs are, by nature, very social creatures and the speed and positioning of the tail wag is part of the body language with which they communicate.

There are several wagging positions that are fairly easy to understand. Within the pack situation it is the dominant dog that holds its tail high and travels with a full wag. When encountering the dominant dog, one of lesser status will hold its tail lower and wag it in a more submissive way. When a human encounters a strange dog it pays to notice the positioning of the tail along with other body signs. A full tail wag can be a greeting, but if the tail stiffens to where only the tip is moving, then there is a

greater chance the dog is feeling challenged and

may attack. — edubook.com