Fast tail wagging often reflects a happy, excited dog. The muscles move the tail side to side rapidly.
When a dog wags more slowly, it may indicate insecurity or apprehension about a situation.
Higher tail wags tend to mean happier dogs. Lower tail positions can mean a dog is uneasy.
Studies show dogs wag more to the right when seeing something pleasant, and more to the left when stressed.
Dogs wag to communicate with other dogs. Different wagging patterns can share their feelings.
Rapid wags also spread a dog's scent, allowing them to share their presence.
Subtle, gentle tail wags can be a calming signal to other dogs not to be threatened.