Why do dogs wag their tails?
Dogs wag their tails mainly to communicate with other dogs and people. A wag can show happiness and excitement, but it can also signal nervousness, alertness or even aggression.
The speed, height and direction of a wag all carry meaning. A loose, wide wag with a wiggly body usually means a friendly, happy dog. A tail held high and wagging stiffly can signal alertness or a challenge. A low tail wagging quickly may show nervousness or submission.
Research has suggested that dogs tend to wag more to the right when they see something they like, such as their owner, and more to the left when they see something that makes them uneasy. Other dogs seem to notice this difference and react to it.
Reading the whole dog
Experts recommend looking at a dog's whole body, not just its tail, to understand how it feels. Ears, eyes, mouth and posture all matter. Puppies usually start wagging their tails at about three to four weeks old, when they begin interacting with their littermates.
Did You Know?
Dogs rarely wag their tails when they are alone. Wagging is mostly a social signal used when another person or animal is around.