What can my dog's tail posture tell me about his state of mind?

What can my dog's tail posture tell me about his state of mind?
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Just as people shake hands and high-five when they meet or play, dogs sniff and wag their tails in greeting. But a wagging tail doesn’t always mean “pleased to meet you!” To gain insight into a dog’s state of mind, you must look at both the tail’s movement and posture.

Most dog owners know that a tail held high and wagging with enthusiasm means it’s great to see you. But beware the tail held high and the wag a mere quivering at the tip. Such a dog is ready to attack.

Alpha dogs let the whole pack know who is boss with a high, stiff tail that wags fast and wide. Fearful dogs show submission with a low tail, wagging almost between their hind legs. Dogs with docked tails often use their entire hind quarters to send information.

– Dr. Larry McDaniel, DVM for the “Purina® Animal Instincts” Podcast Series