Most dog owners can spot the well-known signs of fear in their dogs, such as pacing or tucking the tail between the legs. There are more subtle behaviors, however, that dogs display long before the obvious signs. To help keep your dog happy and comfortable, the American Kennel Club shares the early signs of anxiety. Among them: McClatchy-Tribune Newspapers
Panting: A common misconception is that dogs pant only because they're hot. Actually, many dogs will pant when they're stressed or anxious. This happens because your dog's adrenaline is released in response to a scary situation, and his pulse quickens and his breathing speeds up.
Yawning: Dogs may yawn as a sign that they are conflicted or uncertain about the situation they're in. For example, your dog might want to jump off the groomer's table because he's anxious or afraid, but he's been trained not to do that. Yawning signifies the conflict of continuing in the uncomfortable situation.
Lip tension: Dogs often pull their lips back slightly when they're anxious. It can appear as if he's smiling or just as some creases at the corners of his mouth.
Displacement behaviors: Your dog may display inappropriate behavior because he is anxious or excited about something else. Such behaviors include your dog humping your leg when a visitor comes to the house — he is displacing his feelings about the guest arriving.