Dog leash aggression is usually caused by frustration and often made worse by owner anxiety. Wearing a leash doesn't come naturally to a dog, so proper leash behavior must be trained.
Causes of Leash Aggression
If your dog shows aggression toward people or dogs only when on leash, his aggression was probably caused by frustration. Leash aggression of this type starts with a dog who is so excited when he sees another dog that he can barely contain himself. He may pull or bark. His owner may get frustrated and yell at him or give a leash correction. As time goes on, this turns to frustration and eventually exhibits itself through aggression.
If your dog show aggression when he is also not on leash, this is most likely caused by fear. Your dog is afraid of whatever is causing him to react, and the leash removes his opportunity to escape rather than react. This is made worse by owners who force their dogs to greet, even though they are afraid. Owner Behavior
Leash aggression is made worse by the way an owner reacts to the aggression. As the reactions get more severe, the owner naturally gets more and more nervous. This is understandable but makes the problem worse.
If you tighten up on the leash, you are sending the message to the dog that you, too, are afraid, which confirms your dog's fears. If you use a choke or prong collar to correct your dog during the reactions, he also learns that other dogs are bad-they cause him to be punished.
Thus, when you see another dog, you want to keep your arms relaxed and the leash loose. Say, "look a dog" or something silly in a happy voice. If you find yourself tightening up and holding your breathe, sing a silly song such as "Happy Birthday" or "London Bridges" to reduce anxiety. Stay far enough away from the stimulus that you can maintain your calm. Training New Behaviors
To reduce leash reactions, train your dog to respond to your voice commands, helping you avoid leash corrections. Teach a watch command by saying "watch" and rewarding your dog if he looks at you. Do this in your home at least 25 times per day. Handfeeding your dog's meals is a good way to teach this. Say "watch" and give a handful of food.
When your dog can do it perfectly in the house, try it in the backyard, then the front yard. Gradually build up to even more distracting environments such as parks and walking trails. If you see another dog, say "watch." If your dog looks at you instead of the other dog, give a reward. Feed that the entire time until the dog is gone.
Then, the sight of another dog is associated with pleasure. If your dog ever reacts, you're moving too fast. Go back to the last level where he was successful.
If you practice this each time you walk, your dog will soon react with eye contact rather than aggression. This will have your dog be less fearful and anxious, and improve enjoyment for both of you on walks.