The next step is to countercondition the dog to people and situations that trigger aggression. All exercises should be performed on lead, preferably with a head halter, and basket muzzle, if necessary.
The key point to remember is not to suddenly expose the dog to the full intensity of the stimulus but to very gradually "up the ante." At no point should the dog be allowed to become aggressive during training. If he appears agitated, the training has proceeded too quickly and the owner must return to an earlier stage. For desensitization, the owner should start by exposing the dog to people that he is least likely to be aggressive towards and train the dog in a location where he is most comfortable. Ask the dog to "sit and watch me" or remain in a "down-stay."
Introduce a mildly anxiety-inducing person at a distance. For example, it may be possible to cue the dog to lie down in a relaxed posture, or sit and watch his owner, while a stranger walks by the end of the drive, rewarding the dog with a food treat for remaining relaxed, calm, and in position.
Next, the stranger may stop at the end of the driveway and momentarily walk onto the dog's property before leaving again.
After doing this several times, eventually the stranger should be able to stand a few feet from the dog while it remains calm and under control. At this point, the stranger should be asked to toss one of the dog's favorite food treats toward him.
Next, the dog can be trained to rest on a training mat or sit while focused on the owner when a visitor approaches the door.
Once the dog calmly accepts the stranger's approach, the visitor can knock, and eventually enter the home as long as the dog remains quiet and relaxed. Treats should be supplied if the dog remains calm. If the dog prefers, visitors can present the dog with a tennis ball or other preferred toy.
If these exercises are performed frequently enough, and with an assortment of strangers, starting with the least threatening and working up to the most threatening, the dog will learn that their presence is associated with positive experiences. This concept will replace the prior aversion and need to repel borders. If the dog is resistant to remaining still, an alternative strategy is to have the person stand still and walk the dog around the person in progressively decreasing circles.
During the early stages of training, assistants should be advised not to make direct eye contact with the dog and not to approach the dog head on. Rather, they should be asked to avert their gaze and advance slowly in a circuitous path (as this is less threatening to most dogs). No stranger should reach toward the dog at this stage.
If the dog cannot maintain the required posture and affect, and remains tense, barking and lunging at the stranger, the owner needs to return to an earlier phase of training. Ideally, during the training process, no one should come close enough to the dog to trigger an aggressive response. If someone approaches too closely, and the dog becomes aggressive, the assistant should stand still until the owner can get the dog's attention, preferably using an obedience command, like "cut" [it out], and rewarding the dog for its compliance. The owner can then ask the person to quietly retreat to a distance at which it was previously comfortable and resume training (as long as the dog is not too aroused).
For dogs that are aggressive when people enter the house, it is best to isolate the dog at first and then, once everyone is seated, the dog can be brought into the room on a lead and head halter, if he remains relaxed. At this early stage of the treatment program, if the owner has the dog in the room with guests, the dog should be removed before the guests prepare to leave.
Once the dog remains relaxed when people are quietly sitting in the home, he can be taught to accept them moving about. Owners can start by having the guest slowly stand up and then sit down. If the dog does not respond aggressively, visitors can be asked to try taking a few steps before returning to their seat. The amount of movement the dog will tolerate, while remaining relaxed, should be increased incrementally. Bear in mind that dogs with fear-related aggressive behavior have a tendency to snap at people when they move away, for example, when they are preparing to leave. If the dog is sitting or lying down and appears relaxed in the visitor's presence, the visitor could slide a small food treat toward the dog, if this will not startle him. The goal is to teach the dog to associate visitors' presence with pleasant experiences.
Once the territorial dog is reliably relaxed with visitors in the home, he can be permitted to interact with them. The dog should initiate all interactions with visitors in the home. If the dog chooses to approach a guest, have the person quietly offer their hand for the dog to sniff and they may offer a treat if the dog is not too "grabby." If the dog indicates that he would like to be petted, the guest may do so briefly, but again they should avoid reaching up and over the dog's head and they should avoid prolonged eye contact.
These exercises should be repeated with a variety of different people. Assistants and visitors should be asked to engage in a variety of different activities so the dog learns that they are not threatening.
Avoid Punishment and Reassurance. Whenever the dog is behaving in an aggressive manner he should be ignored or controlled. Neither punishment nor reassurance are appropriate actions. Punishment has the potential to increase the dog's anxiety and worsen the situation. Reassurance will affirm the dog's fear.
Territorial aggression, when confined to barking at the sound of approaching strangers can be a bane or a blessing, depending on the circumstances and the owner's control of the situation. If it is a bane, the owner can do something about it using the approaches described above, and can frequently make inroads into containing the problem. Territorial aggression that has advanced to the point of lunging, snarling, and biting is more difficult to treat and positive results, though eminently possible, are not guaranteed.
For difficult cases, it may be helpful to treat territorially aggressive dogs with anti-anxiety, anti-aggressive medication. Clomipramine (Clomicalm®), fluoxetine (Prozac®), buspirone (BuSpar®) are all reasonable treatment options. The efficacy of such treatments will vary from case to case but price, side effects, and other logistical concerns will determine the order in which these treatments are tried. Most medications take several weeks to achieve their peak effects. Typically, these treatments are applied for at least four to six months, and possibly for as long as a year or two. Needless to say, appropriate behavior modification therapy should be conducted simultaneously to take advantage of this therapeutic window.