Dogs do speak - with their bodies. Close observation can tell volumes about their mood. No single cue is sufficient. Look instead for a combination of non-verbal signals. A wagging tail is not necessarily a sign of a friendly dog.
The following are five basic archetypes of canine body language:
A friendly dog is a relaxed one: perky ears, wide open eyes, alert, possibly a wagging tail and its weight distributed equally front to back. He may or may not acknowledge your presence. This describes the majority of dogs you will encounter.
This is a friendly dog with more pep! You'll see excitement, such as panting, wiggling and bouncing up and down. It may also extend play invitations by running to and fro and play-bowing, in which it lowers its front end and keeps its rear end in the air. He will probably acknowledge your presence.
If you do not desire to interact with these dogs, do not make eye contact and fold your arms across your chest. If it appears that they may jump on you, simply bring your bended knee up to thigh-level, so the dog will hit your knee as it jumps. This action keeps the dog off you, but should not be used to hurt it. You can also turn your back on the dog and stand still until they pass.
Dog walkers: If you know your dog likes to visit and won't respond to your command to come, consider clipping your leash to his collar before you cross paths with trail users such as children, individuals who appear unsteady on their feet or who are wheelchair bound, other walkers with dogs on leash, or those who are walking without dogs.
By far, these playful, exuberant canines are the ones creating the most dissension on trails, through no fault of their own. Though we enjoy our dogs and their playful antics, some trail users are very uncomfortable with out-of-control dogs that jump on them or run at them in play. As a community of dog owners, if we want to retain our privilege to walk off-leash on local trails, we need to exercise a bit more control of our enthusiastic companions.
This dog may be frightened, unsure or intimidated. Its body language conveys to others "I'm no threat", as it cowers on the ground, ears penned against its head or down, tail between its legs, trying to make itself as small as possible. Sometimes, it may roll over onto its back. This dog is rarely a problem for human beings or other dogs, with its low self-confidence and non-dominant personality. Please only approach this dog if you have the owner's permission.
Dog walkers: Please be considerate of a submissive dog and its owner by calling your dog to sit by you or leashing it. This allows the submissive dog to approach on its own terms.
This dog displays some of the same body language as the submissive dog. However, its body is tense and may tremble. Its lips draw back to expose teeth. You may see the eyes narrow or roll back up in the head, leaving the whites showing.
This behavior indicates the dog feels threatened or trapped, and cannot escape from what is frightening it. If provoked, it may try to defend itself by biting or fighting. Move quickly past this dog without interacting.
Dog walkers: Please be considerate by calling your dog to sit by you or by leashing it until after the fearful dog has passed by.
This dog looks menacing as it projects its weight to the front of its body and stares hard at you in the eyes. Its teeth may be bared; legs stiff. Some of the hair along its spine may be standing on end. Many times, its tail will be held out rigid from the body, with the hair on it fluffed out like a bottle brush. You may hear a snarl, growl or loud bark.
Do not interact with this dog. Do not look it in the eye. Back up slowly and leave or give it a wide berth.
Dog Walkers: If you own such a dog, consider exercising it at home or keeping it on leash in public at all times.
These are general guidelines. If you are unsure of a dog's body language, the safest policy is to not interact with it.