Most dog owners can read the basics of what their dog is telling them, using the dogs body language. For example, we most likely know when our dog wants to play with either us or another dog as they will "play bow", where their front end will go down in a bowing motion. Usually, we can also tell if our dogs are happy, fearful or anxious. However, we have lost the ability to read the more subtle things that dogs tell us through their body language. Dogs on the other hand, know exactly how we are feeling by looking at our body language, they read us constantly, whatever we are doing.
Happy dogs usually appear more relaxed, and a tail that wags loosely either side to side or like a helicopter blade, along with the rear end of the body wagging too. Some dogs even "smile" when they greet by pulling back the corners of their mouths. Their approach to you will be comfortable and showing no signs of fear or stress.
The wagging tail, however, does not always mean a dog is happy. Dogs that are scared will have their tails low, usually between their legs, but still wagging. Confident and sometimes aggressive dogs will hold their tails high and wag it stiffly.
We should all teach our children these signs as they are easy to remember and could help avoid an attack.
Anxious / Fearful Dogs
Dogs, like most mammals, have a fight or flight instinct. Quite often, dogs will show signs of both of these, they will lean back on their hind legs, so that they can flee quickly if need be, along with putting their heads down to deliver a bite. Their tails, as previously mentioned, could be between their legs, possibly wagging. Their ears will be back, they will take short quick breaths and their eyes will be wide showing the whites of their eyes. Yawning is also a way that dogs display anxiety, this should not be mistake to mean that they are tired. Frightened dogs will also put their hackles (the long hair on their neck/back) up to make them look bigger.
We should watch out for these signs when our dog meets new dogs, so that if they display any of these we can move them on quickly and calmly.
Submissive / Appeasement Behaviours
Some submissive dogs will try to show appeasement to more confident dogs in order to avoid potential aggressiveness towards them, this could include licking their lips, muzzling or licking at the other dogs face, and sometimes jumping up. Very submissive dogs will lie down and sometimes even curl into a ball to make themselves look as small as possible to help appease the other dog. Dogs can also look away slightly, sniff the ground, scratch themselves or shake their body (such as when wet) to calm a situation or divert the attention away when they feel threatened by another dog or human.
Most of the time, aggression within dogs is easy to see. They will lean forward, and look at the face of the person or dog while showing their teeth. They will not look away from their target, and the dog will show focus. Dogs sometimes may jump forward, snack at the face of the dog/person or the air in front of them then back away again, basically to say "leave me alone" as a warning.
As most owners well know, if our dogs want to inflict harm then they are more than capable of doing so, most of us have seen our dogs hold on to their toy and shake it. This behaviour is usually intended to kill (ie terrier with a rat).
It is extremely unusual for a dog to bite for no reason, and the majority of times people are bitten, they have completely missed the warning signs from the dog, the same signs would have easily been read by another dog which would of backed off.
Alert or interested dogs can easily be mistaken for aggressiveness as the dogs will have the same stance, tail position and body stiffness, we should be quick to call the dog back if we notice this as it could be that a dog has seen a cat and preparing to give chase.