This article was kinda interesting.
Without a sound, two properly socialized dogs meeting for the first time can size each other up in just a few moments. An exchange of glances can tell each canine if they're going to be friends or enemies.
How can dogs do this without a sophisticated verbal language? The answer: facial expressions, body language and posturing. Although dogs signal intent by barks and growls, the message is not complete without the telegraphy of body and facial language.
Various parts of the dog's body are involved in this form of communication. Here is a quick primer in canine body language.
Facial Expressions
A combination of facial expressions communicate a dog's mood and intentions that can be understood by other species, including humans. Here are a few examples of facial communication:
Relaxed mood: Soft eyes, lit up, looking – but not staring. Ears forward or flopped, with tips bent over (if anatomically possible).Mouth open, lips slightly back, giving the impression of smiling. Tongue hanging limply from the side of the mouth
Anxiety: Eyes glancing sideways or away. Ears to the side of the head or flopped. Teeth clenched, lips firmly retracted. Tongue either not evident or lip licking
Intimidating: Eyes staring like searchlights. Ears forward. Teeth bared
Fearfulness: Eyes looking forward or away, pupils dilated. Ears pressed back close to the head. Panting/breathing hard through clenched or slightly open mouth. Jaw tense so that sinews show in the cheeks
Stress: Yawning plus other signs of anxiety or fearfulness (as above)
Head-Neck Position
Head down (“hang dog”): Submission or depression
Head in normal mid-way position: Everything is all right
Head/neck turned to side: Deference
Head held high/neck craning forward: Interest or, depending on other signs, a challenge
Head resting on other dog's back: Demonstrating dominance
Torso/Trunk/Upper Limb
Tensing of muscles and the raising of hackles: Threat/imminent fight
Gestures
Play bow – head low, rump elevated: The universal sign of canine happiness and an invitation to play
Paws on top of another dog's back: Dominance
Looming over: Dominance
Rolling over: Submission/deference
Urinating by squatting: Deference
Urinating by leg lifting: Dominance/defiance
Humping: Dominance
Backing: Unsure/fearful
Tail Position
Tail up: Alert, confident, dominant
Tail wagging: Dog's energy level is elevated (excited or agitated)
Tail held low or tucked: Fearful, submissive
Tail held horizontal and wagging slowly: Caution
Tail held relaxed and stationary: Contented dog
There is no one sign that gives away a dog's feelings but if you consider all the body language signs, you can get a pretty good idea of what's going on in the dog's head. A dog that is staring at another dog, his ears pricked and his tail stiff, is probably conveying dominance, or at least a wish for it.
A dog that averts his gaze from another dog and hunkers down nervously as if waiting for an explosion is likely fearful and is trying to defuse the situation by acting submissive.
Sometimes body language signs can be ambivalent, however. For example, it is not uncommon to observe a dog growling at another dog while occasionally glancing to the side, backing up, and with his tail wagging. Such a dog is invariably fearful. Whenever fear signs are present, fear is in the equation. These dogs are unpredictable with other dogs and will alter their body language and behavior according to circumstances. If the opposing dog retires, they may jump around and “look happy.” If the opposing dog approaches too close the fearful one may snap or bite. Owners, if present, can help defuse their dog's ambivalence and uncertainty by taking a strong leadership role. It's amazing how rapidly a fearful dog's disposition will change when an authoritative owner steps in and controls the moment. Dogs need strong leaders.
Another aspect of communication is odor. Because dogs have such an amazing sense of smell, it is likely that they learn a lot about other dogs from their smell. That's what all the sniffing is about. It is difficult to imagine what sort of information passes between dogs via this medium. We do know that intact male dogs “smell male” (because of male sex pheromones) and that neutered males do not have this characteristic musk. By neutering males, we alter the olfactory signals they emit and thus other dog's perception of them. It may even be that the "non-male smell" equates with a diestrus (in-between heat periods) or a neutered bitch smell.
When an intact male dog meets a neutered one, the response may not be confrontational because the other dog doesn't perceive a rival. He may believe the neutered dog is female.
Non-verbal communications signaling “let's play,” “leave me alone,” “who do you think you're talking to,” “I'm not going to cause you a problem, I promise,” are going on all the time between dogs but many dog owners don't realize it. It's amazing what can be conveyed with the odd glance or posture. Some dogs are masters at such subtle language.
The worst canine communicators are those dogs that have been raised without the company of other dogs during a critical inter-dog socialization phase of their lives (3 to 6 weeks). Hand raised orphans provide an extreme example of what may be lacking. Many of these dogs are socially inappropriate having not learned canine communication and social etiquette. They may attack and continue to attack another dog when the psychological war is already won. They may not know how to signal defeat when they are being attacked themselves. And that's just the (extreme) tip of their communication failures.
Most dogs are not this “dyslexic” and can communicate what they need – as with humans – but the good communicators usually have the edge. Fully functional body language is a beautiful thing that can help resolve uncertainties at a glance. Humans communicate in body language too. We're just not so good at it and some of us are positively stiff. If dogs could talk they'd probably categorize us as “dumb animals.”