There are many different potential causes of aggression. It may be hereditary, although it shouldn't be if you got your boxer from a reputable breeder. Genuine hereditary aggression is rare in domesticated dogs of most breeds. Aggression may also result from a health issue. However, the most common cause of aggression is the result of lack of adequate socialization and training, which includes some basic misunderstandings and poor timing or mismanagement of a situation.
Owners frequently reward undesirable behavior inadvertently. This might be as subtle as taking a secret little pride in your boxer's protective or macho side, or as obvious as not correcting him when he growls. This can have the unfortunate result of making it occur again and again. Aggression may also occur as a fundamental misunderstanding that socialization must continue to occur throughout your boxer's life, and it has not on the part of the humans involved.
Aggression is a natural and, to some extent, a necessary phenomenon in domestic canines at times. After all, it is the only method that really allows them to make a point after everything else has failed. It does not necessarily mean the end of your relationship with your boxer, but it does mean that you need to step back and re-evaluate the situation.
If you have missed out on some of your boxer's early education, or missed some cues that all is not going well, and your boxer has acted inappropriately, what's the solution? First, you can work harder at exercising your boxer physically and mentally. This may mean longer walks and longer training sessions and even more playtime. Whatever makes your boxer tired and happy will help to work off the inclination to be aggressive. This is an example of expending the energy of aggression.
Alternatively, you can change channels on your boxer. Boxers, which tend to be the drama kings and queens of the dog world, are very susceptible and responsive to a change of attitude. So, if your boxer is showing signs of dominance or aggression to other dogs, for instance, you can say something like “Phooey” and show disappointment, or shame or ridicule, “Oh no, you're being bad,” or “You've got to be kidding.” Your boxer will probably shift attitudes right along with you.
Of course, like any other type of training reinforcement, you have to be vigilant about when this type of attitude occurs. Try not to miss any opportunities over a period of about a month or more, during which you should reinforce constantly to your boxer that you don't approve of or agree with his negative assessment of the situation. When you do this, you need to move out of the area of the dog in question just in case your boxer is picking up something bad in the other dog's attitude. Usually, if you remove your boxer from the situation, the other dog will give it up as well.
If your boxer is aggressive with other dogs you must keep him away from others until he can behave.
Aggression and Drive Triggers
In any event, you need to carefully assess what triggers your boxer's aggression. For those dogs that have high prey drives (many dogs in agility and obedience), almost anything that moves can trigger this drive. That may be bikers, joggers, smaller dogs, cats, squirrels, cars, or even children.
The first solution is not to let your boxer off leash so that he can chase anything he wishes, and to work on your recall games to strengthen that part of the equation. Secondly, lots of exercise is a must, and a lot of retrieving will often help. The boxer often does well with scent training, as it makes him use his brain, and that is always challenging for a dog. You can do this by hiding his toys around the house and having him find them, or by teaching formal scent-retrieve exercises. He will need to be put on a sit/stay or someone should hold him back while you hide the toy. After a few rounds of this game, your boxer will be tired, as scenting wears most dogs out more than almost any other exercise.
For a dog that is naturally dominant, you need to use a different tactic. The dominant pup is often one that gets things quickly and appears to be following all the rules. What he is really doing is figuring out how long it's going to take him to take over. Often, with a pup like this, the first thing that shows you a sign of him being dominant aggressive is that he growls at a lesser pack member or guest when told to get off the couch.
To curb aggression in a dominant dog, play tug of war with your boxer. If he's a pup, be careful not to let him tug to the point of dislocating his jaw or pulling his bite out of alignment. Always let your boxer win, but when the play session is done, be sure to take possession of all the tug toys and put them away. Another trick for a dominant dog is to practice lots of long downs. This reinforces to your boxer that you are the ultimate pack leader, and the exercise gives him time and a lowly position to consider it.
This is the pup that needs strong guidance and a strong pack leader, and he needs to have rules firmly enforced by other family members as well. If your boxer is a very dominant pup, when he grows up, he will be the one who puts his head across another dog's shoulders or neck. If the other dog agrees that your boxer is dominant, he will crouch down and accept your boxer's position. If not, a fight will ensue. Try to avoid this. Some boxers learn to love to fight, and they often win.
While games and more training should help ease aggression, sometimes these methods aren't enough. If you are afraid of your boxer but don't want to give up on him just yet, get a humane muzzle. This takes the decision-making ability away from him and reinforces your position as the dominant one. The muzzle is a not-so- subtle dominance inhibitor. Once the muzzle is on, you can go back and retrain, hopefully making up for those things that he missed in his early education.
Early Separation from the Litter
One type of aggression tends to occur in those pups that have been taken from their mother and pack before the age of seven weeks. If you got your boxer from a reputable breeder, this probably won't happen. However, if you got your boxer from somewhere else, your boxer could show signs of aggression to people with no warning. He could attack other dogs with no warning and might be inclined to not stop biting even after the other dog submits.
If your boxer left the pack before about seven weeks of age, he may have missed those lessons on bite inhibition. He can't interpret body language well and isn't entirely aware of the consequences of his actions. In these cases, if a fight ensues, it can be very hard to stop. In a multidog household, these sorts of attacks can arise if your boxer becomes jealous of another dog getting attention. It is sometimes also a problem with older dogs and rescues.
Aggression is a double-edged sword. On the one hand, it can have some very negative ramifications, but on the other, it can tell you a lot about your boxer that can help you to take a positive direction with him. Aggression does not have to be the end of your canine/human relationship.
The principle retraining of this dog is to reward him for being calm in an ever-diminishing territory. Put your boxer on a leash and have a person walk by, first at a distance and then closer. Give your boxer a treat every time he does not react in any way to the person's presence. In this way, you familiarize your boxer with nonthreatening strangers or other people. The best social solution for this dog is that you tell people to ignore your boxer when they come to the house, especially if he is not acting out in an aggressive way. Give your boxer the chance to accept them and to work up the courage to make friends, or at least keep his distance.