How to deal with an aggressive dog
Understand that what a person may see as an unprovoked aggressive act in a dog may, in fact, be perfectly logical to a canine mind. The major determinants for aggression in dogs are discussed below.
Dogs will express this form of aggression when defending their territory. This is any territory that the dog is familiar with or has marked with it's scent. While you may encourage your dog to protect your property, the dog may have a larger estimate of "his territory" and view the whole neighborhood or block as his territory to protect.
Many dogs tend to guard both possessions, and members of their pack. This may include people, other family pets, and even favorite toys and sometimes food items. This "Guarding Aggression" is directed at unfamiliar people or animals that are approaching the dogs people, possessions or food. Occasionally, the dog will even guard food or toys from familiar dogs or people.
Transferred Aggression often happens when a dog becomes upset or over-excited and instead of becoming aggressive with the specific item, it transfers its aggression/frustration onto another dog or person. For example a kid may poke a dog with a stick through a fence, and since the dog cannot defend itself because of the fence it may turn its aggression on another person in the yard or on another dog.
Pecking Order Aggression
Dogs are pack animals, and they need to establish the pecking order or hierarchy with the family or household members (human and animal alike). Once the dog has established his rank in the family he, or she, does not like to be challenged. Often well-meaning owners will inadvertently teach their dogs that they are in fact the highest ranking pack member and that can lead to difficulties in controlling the dog. It is also common for there to be aggression problems between dogs in the same household as they battle it out for the top position.
Aggression Due to Fear
Dogs do respond like humans with a fight or flight instinct when presented with a fearful situation. Dogs that respond with aggression may growl, snarl or even bite if they are frightened. Remember, different reactions in dogs are due to genetic disposition, training methods and past experiences. The dog may see a fearful event in a calm environment if he has been abused in the past. Dogs that would normally use the flight option but are trapped or cornered will resort to aggression in an attempt to protect themselves.
Some dogs will become aggressive when they believe that they are threatened, that their position in the pack or family is threatened, or that their territory or possessions are endangered. As humans we often don't understand all the triggers for a dog to respond aggressively. Aggression in dogs, whatever the reason, needs to be controlled in order to avoid a potentially dangerous situation for both humans and other animals. Positive rewards training works well for these aggressive dogs, and punishment almost never helps and in fact will often make the aggressive behavior worse.