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Dogs respond with aggression for many different reasons. Your dog's aggressive behavior may be triggered by a certain type of person or situation. For example, some dogs become aggressive when new people visit, or when people walk past your dog's yard area. Try to identify your dog's triggers to help you as you attempt to retrain him. Pay special attention to his body language when he is exposed to one of his triggers. Many dogs are fearful or anxious prior to aggression. Common signs to watch for include a lowered head, low body posture, tail tucked between the legs, licking lips, looking away, dilated eyes, shivering or shaking. A dog that intends to attack will make a subtle change in the way he is standing. He will make direct eye contact and stare at his target. Then he will shift his weight so that it is over his front legs. He may also give a stiff tail wag with his tail held low. Watch for these signs because they indicate that a dog is about to lunge. If you are ever faced with a dog showing any of these signs, your best defense is to step aside or away from the dog and avoid staring back at him. Be quiet and calm as you do so. If you notice your dog behaving this way, get him under control with a leash or bring him inside immediately. You will not be able to solve your dog's aggression problem with a single training session. Retraining an aggressive dog takes time. Be patient and take precautions (such as a strong leash and a muzzle) to protect yourself and others as you retrain your dog. Never hit or punish your aggressive dog. Doing so will cause your dog to become over excited, or if his aggression is due to anxiety it will make him more fearful. As a result, his aggression may become worse. To increase your chances of success in retraining your dog, it is a good idea to consider a consultation with a registered pet behaviorist. Aggression has many contributing factors and a home consultation with an expert may give you the best chance of identifying all of these factors and working out the best strategy to control them. For example your dog may have a fear of strangers or other dogs, territorial aggression, or be prone to protecting a resource such as food. Ask your veterinarian for help finding a registered pet behaviorist in your area. While you are retraining your dog, try to avoid his triggers. This might mean changing your walk route to something that is quieter and less used by dog walkers or playing vigorous games in the yard to burn off energy rather than going to the park.
Think about what triggers your dog's aggressive behavior. Get into the habit of reading your dog's body language. Learn how to recognize common signs of aggression. Understand that there is no quick fix for aggression. Consider having a consultation with a registered pet behaviorist. Change your routine to reduce exposure to triggers.