There are several reasons why your pet may display an aggressive dog behavior. Unfortunately, since we don't understand dog language, we may think that dog aggression is just something dogs are born with to make their human masters' lives miserable. It is important to understand that the first step to solving problem behavior among dogs is to first understand the reasons behind them.
Fear Aggression
Your dog could be showing aggression simply because it is afraid. Like a human being, a dog will do its best to fight against forces that it sees as harmful. Sometimes though, the sources of dog fear may not really pose any real threats. A hand gesture from you or the act of picking up something may be incorrectly perceived by dogs as intentions to hit it or pick an object to hit it with. In these cases, a dog's natural defense would be aggressive behavior.
Fear aggression, in many cases, is a learned response. Your dog may have had a traumatic past. He may have previously had violent owners. He may have been chained for long periods of time, hit repeatedly and deprived of food. Dogs that have had bad experiences in the past may be more defensive, suspicious and aggressive than normal.
Possessive Aggression
Dogs do think of some things as their own, too, just like humans. A dog's possessions may include its house, food dish and toys. In a way it may even perceive you and your family as part of its possessions. Aggressive dog behavior may therefore be shown because your dog simply wants to protect its own. It may become aggressive towards outsiders or even to members of your family if it thinks that its possessions are threatened. The well known territorial aggression is the same as possessive aggression. Areas that have been marked by your dog with its urine cannot be shared with anyone else.
Dominance Aggression
Before dogs were domesticated, they lived in packs. Animals that are related to dogs such as wolves continue to live in packs in the wild. In these groups, a clear hierarchy is formed. There is always an alpha male and an alpha female. Your aggressive dog may merely be simulating this age old tendency of its species to form hierarchies.
Your dog might still feel that it is a dominant dog and that you are a lower member of its pack. Fighting a dominant dog with aggression may only reinforce its aggressive behavior as it attempts to fight you for the top spot in the pack.
Redirected Aggression
Sometimes we aren't allowed to express anger or aggression. We therefore look for objects and situations to vent out our feelings on. Dogs are the same. If they feel some form of aggression for another animal or for another pet in your home, their owners would naturally want to stop them in any way possible. This could push dogs with pent up aggression to channel their energies elsewhere. This is bad news for you because you could be the nearest recipient of a big bite intended for another person or animal.
You can't let aggressive dog behavior pass. There is a real need for you to find methods and techniques to train your dog to react in non-aggressive ways.