Reasons why a dog may be aggressive
Aggressive behavior can be caused because your dog wants to establish dominance. Dogs are pack animals and there is always a leader within the pack. Your dog may want to be the alpha dog leader. However, you need to be the alpha dog so let your dog know that you are the leader of this pack. He may still act aggressively towards other animals or other dog's as there is a hierarchy to the pack. This may be one reason why your dog acts aggressively.
Another common form of aggression in dogs is territorial aggression. Your dog will relentlessly protect everything that he considers to be "his" including yourself, your home and your family. While this can be a good thing if you are threatened at some point, it can cause many problems in regular situations. It is seldom that a family is truly threatened and if your dog's territorial aggression is out of control it can cause issues with visitors and neighbors. Excessive territorial aggression is inappropriate behavior.
A dog's aggressive behavior can be misdirected. Something happens that causes the dog anxiety yet he is not able to take his aggression out on what really caused the aggression so he takes it out on something else. This may be a reason why your dog may be fighting with other dogs for no obvious reason. He is releasing his anxiety and aggression that was caused by something else.
Sometimes aggression can be caused by a biological or medical reason. For example, we all understand that a mother dog may become aggressive when she is protecting her litter. Less understood though is that sometimes aggression can be caused by a medical reason. That is why it is crucial to take your dog to the vet for a complete examination to rule out any medical problems.
Spaying your female dog and neutering your male dog will usually help calm excessive aggression. Your training efforts will also be easier and more effective. If you are not planning to breeding dogs, spaying and neutering is the responsible thing to do.
Your training efforts to curb aggression will be more effective if you take into consideration the reasons why your dog is being aggressive. Understanding the causes for your dog's aggressive tendencies can help you to tailor your training efforts to his needs.