Dog Body Language
People often assume that a dog with a wagging tail is a friendly dog, but this is far from the truth. Dogs wag their tails for numerous reasons, including when they’re feeling aggressive. And a dog who isn’t wagging his tail can still be friendly. A dog’s ability to use his tail to express how he feels is limited by the type of tail he has. Most dogs have a “natural” tail that hangs down to somewhere near the hock (the joint between the lower thigh and the pastern on the rear leg). Others, such as the pug, have tails that curl up and over their backs. A few breeds, like the greyhound and whippet, have a tail that naturally tucks slightly between their rear legs. And some breeds have naturally short bobtails or have tails that were surgically docked. (For example, Australian shepherd puppies may be born with natural bobtails, and the Doberman pinscher is a breed that often has the tail surgically docked.) Because it’s a painful procedure done only for cosmetic reasons, the ASPCA does not condone tail docking.
When your dog is relaxed, he’ll hold his tail in its natural position. If he’s feeling happy, he may wag it gently from side to side. If he’s really happy, like when he greets you after being apart from you, his tail will wag more forcefully from side to side or might even move in a circular pattern. If your dog feels nervous or submissive, he’ll hold his tail lower and might even tuck it between his rear legs. He may still wag it from side to side, often at a more rapid pace than if he’s relaxed. If he’s really scared or feeling extremely submissive, he’ll hold his tail tucked up tight against his belly.
When your dog is alert or aroused about something, he’ll probably hold his tail higher than normal. He’ll hold it stiff, without any movement. If he’s standing his ground or threatening someone (a person or another animal), he may “flag” his tail, which means he holds it stiff and high and moves it rigidly back and forth. It might look like he’s wagging his tail, but everything else about his body tells you that he’s not feeling friendly at the moment.