Dogs often are aggressive to other dogs because of instincts that come from their canine background in general. They are pack animals and use domination in attitude and physical aggression to place themselves in positions of power in the pack. Other reasons for a dog's aggression to another dog can come from their inherent instinct of breed type and drive. German shepherds are herding dogs and their natural desire is to get other animals to do what they want them to do and go where they want them to go. That, along with a strong pack instinct, can create some problems in a multicanine household or when you want your German shepherd to behave in a group of strange dogs.
Instructions
How To Train a German Shepherd Not to Bite other dogs
Learn about general canine behavior to understand how your German shepherd reacts to other dogs. Too often, we expect dogs to behave like four-legged humans. They become confused and aggression can be fueled to a greater degree.
Pay attention to the body language of your dog when around other dogs. As your dog's owner, it is your responsibility to keep them out of situations that are likely to fuel aggression, such as being in the vicinity of other dominant dogs, and in some cases around subordinate dogs.
Realize you will have trouble keeping two dogs with a dominant personality in the same living space without strict rules and separations.
Use quick sharp corrections if your German shepherd becomes aggressive toward other dogs at home or in a public place. This means having them collared and keeping them on a leash so you can deliver a quick snap of the leash and a firm "no" to the first signs of aggression. Early signs an aggressive attitude is forming toward another dog are strong, consistent eye contact, growling and hair standing on the back of the neck.
Understand you can control your German shepherd's behavior while on a leash but might never completely teach them not to assert themselves in a dominant manner toward other dogs. Biting is a common method of asserting superiority between dogs, and when two animals are engaged in a confrontation and are not willing to give in, the biting quickly escalates into a violent situation.
Become the pack leader. This is very important with any large dog, especially if they are "alpha" personalities who wish to be dominant members of a pack. You are a part of your dog's pack and if you are not the leader, you are the subordinate and your dog will not listen. One method of showing your dominant position is to put your dog on his back and hold him there with you above him while holding a firm eye contact. Do not look away. Stare down your dog until they are forced to look away. This also is a common dog posture of dominant/subordinate behavior.