How to read dog body language

Recently I've had several conversations with other dog owners about how to tell if a dog may be aggressive. Most dogs do not generally want to fight other dogs - ultimately this goes against everything their instinct tells them. 

However everybody will know of one or two pups who start a scrap every so often. To us owners what may sound like a full on fight is often just a squabble over position in the pack. Every interaction a dog has with another centres around establishing social position. This is completely natural and as long as both dogs are calm and under control there should be no cause for concern.

Problems arise however when dogs are in pain, stressed or undersocialised - all of which can manifest in aggressive behaviour towards other dogs. Sometimes it can be difficult to tell whether a dog is a threat or not and this is where a basic understanding of canine body language can prove useful. Take a look at the pictures produced by the American Society for the Prevention of Cruelty to Animals and see how many are familiar to you: