One of the most misunderstood pieces of dog body language is the wagging tail. Most of us have been taught that a wagging tail is a sign that a dog is friendly and wants to interact. A wagging tail is actually a sign of excitement and arousal. The dog may be excited because they want to say hi, but they could also be aroused because they are stressed or concerned. It’s important to look at the dog’s entire body, not just the tail, before deciding if this is truly a friendly greeting.
Is that dog wagging with a tail at normal position (not too high or too low), with broad sweeps accompanied by a wiggly butt and torso? Do they also have a relaxed body and face, open mouth, and oval eyes? If so, they likely are trying to say hi.
On the other hand, if the tail is very high or very low, wagging rapidly, the rest of the body is tense and stiff, the mouth is closed, ears forward, eyes round, and/or they are either retreating or barking and lunging, that dog probably needs some space.
Don’t be fooled by the tail alone – make sure to read the whole dog to understand what they are trying to tell you.