Does the position of a dog's tail communicate how it is feeling?

Yes, the position of a dog's tail will communicate how the dog is feeling. For example, if a dog's tail wags back and forth, the dog feels relaxed. If a dog's tail is standing straight up, the dog is alert and tense. When a dog's tail is tucked down low, it is nervous. If the dog's tail is moving in circles, the dog is happy.