The Mailman Syndrome

A client reports that his dog becomes frantic whenever a mailman or delivery person comes to the house. It attacks curtains and the windowsill and will rip up the mail. Other than getting a post office box, is there anything he can do?

Before addressing this problem, ask the client about other manifestations of aggressive behavior toward people who come to the home. Does the dog growl, snarl, lunge, snap, or attempt to bite visitors? Are the aggressive displays worrisome in other situations? Has anyone received a bite from this dog? If the answer is yes, people who come to the home must be kept safe from injury by the dog. The dog may be dangerous and the case requires intervention by a veterinary behaviorist.

An animal's behavior is influenced by genetics, the environment, and learning. Each contributes to the expression of any behavior, but the contribution of the individual components cannot be easily assessed. Some aspects, like genetics, cannot be changed, while others, such as environment and learned responses, may be more amenable to treatment.

This dog's behavior is probably a territorial response, which is usually directed toward people or animals that are not part of the immediate family but enter an area the dog perceives as its territory, usually the home property.¹ (Some dogs may also guard objects within the home from family members or other dogs, but this will not be discussed here). Any dog may show territorial responses, but certain breeds have been developed for guarding and watchful behaviors. Without appropriate supervision, owner interaction, and training, these dogs may engage in territorial displays that vary from mild barking to intense displays that may include growling, snarling, lunging, piloerection, and biting. Opportunity and access to the stimulus influence whether the behavior will occur. Territorial aggression is usually believed to be a "protective" behavior and includes fear as an additional motivation.² Because of the high arousal level, frustration may also be present and lead to redirected behavior toward objects, other animals, or people. Dogs that are tied may show extreme territorial behaviors and aggressive responses.

Why the Mailman?

Mail or package delivery personnel and trash collectors all present predictable stimuli that agitate many dogs. These individuals have common traits that may contribute to the aggressive arousal. They approach in vehicles that differ in size, shape, and sound from the vehicles the dog commonly encounters. They may wear uniforms and thus look different from people the dog usually sees and carry unusually shaped objects. They come close to the home and linger for variable periods, usually without coming inside. The dog may respond by barking, growling, or running from window to window or along the fence. The longer the person stays, the more aroused the dog may become. The goal of the territorial display is to get the "intruder" to leave. Once the intruder leaves, the dog has successfully accomplished the task, which acts as a potent reinforcement and strengthens the response over time. Dogs may also show similar behaviors when left in a car or may quickly claim a new territory and defend such places as picnic areas or park benches.²

Initial Steps

Changing territorial responses involves several steps. Ensuring the safety of individuals who must come to the home is essential. A dog showing territorial aggression should be removed and securely confined when company is present. An effort should also be made to prevent ongoing territorial displays at windows and fences. This might mean covering windows, preventing access to them, and preventing outdoor access unless the dog is on a leash and collar and is being restrained by an adult. If that cannot be done, then during retraining it may be prudent to have the mail delivered elsewhere. While the dog may still respond to the mailperson being in the neighborhood, the responses may be muted if the house is not directly approached.

Punishment must be stopped because it may increase rather than decrease the fear and anxiety that may be underlying the behavior. Treat­ment and control can be greatly facilitated by the use of head collars or harnesses to provide secure and humane owner control. Teaching the dog to respond to basic commands in nonthreatening situations and when the dog is calm and controlled is essential for progressing to the next step of treatment. Stimuli that provoke the territorial response should be identified and a response gradient determined (i.e., at what distance is the territorial response noted, and how does the response vary with changing distance [approaching and retreating])?

If redirected behavior is part of the problem, it may be necessary to separate dogs to prevent fighting. Owners should not reach for an aggressively aroused dog. While the owners are home the dog should wear a head collar and drag a leash so they can interrupt and redirect territorial responses before they intensify, and reward the dog for the appropriate behavior.

Changing the Response

Some dogs respond well to simple interventions, such as blocking visual access, but others may need more training. Counterconditioning and desensitization are used to teach new responses. First, the dog is taught to be calm and settled while wearing a head collar and on a leash, using food rewards to facilitate learning the new task. Then the stimulus is presented at a very low intensity and the dog rewarded for remaining under control (in other words, work with the mailperson at a distance). Delectable food rewards can strengthen the association and should be reserved only for training sessions. Access to the stimulus should be prevented unless the dog is in a training session. The owner must always watch the dog and be aware of the stimulus so that he or she can interrupt and redirect any inappropriate behavior before it becomes uncontrollable.

In less severe cases, classical counterconditioning may work well within a brief period. In classical counterconditioning, a stimulus (e.g., the mailperson) that provokes a territorial response is associated with something pleasant (e.g., food). When not in a training session, the dog should not have access to the stimulus or the reward. During training, the dog wears a head collar and the owner should hold the leash and stand back from the window. When the mailperson is first seen, the dog is instantly provided with a delectable food treat (such as small bits of turkey hotdog). The dog is continually given the food as long as the person is present, regardless of how it responds. Once the person leaves, the food is withdrawn. The goal is to associate the presence of the mailperson with the food. You are not conditioning the dog to behave a certain way, but rather to learn that when the mailman arrives wonderful things happen, creating an association between the mailman and wonderful events.³

Other Treatment Strategies

Limited research evaluating the effect of diet on aggressive behavior has suggested that low-protein diets may be useful in dogs showing territorial aggression, especially in those that also show fearful responses.^4,5 When anxiety and fear are components of the response, dogs may benefit from medications, such as selective serotonin-reuptake inhibitors or tricyclic antidepressants.⁶ Few medications are licensed for use in companion animals and owners should be informed of the extra-label use. Medications and dosages are discussed in other sources.⁶

Prevention

Prevention is always preferable to retraining. Frequent encounters with new people while the owner provides food reinforcement to a young dog can often be preventive. Interrupting and redirecting territorial responses early on is desirable. If the behavior is extreme and difficult to control or allowed to occur without owner intervention, this approach is unlikely to be successful. Associating the mailperson with dog treats from the beginning may teach the dog that the mailperson brings good things for them as well. Good owner control and response to commands can help calm the dog and teach it appropriate responses.

Many dogs are amenable to changing territorial behaviors. However, allowing the dog to have access to the stimulus without owner control and intervention reinforces the behavior, and it is likely to continue. Because territorial responses tend to increase over time and can result in human injury, early intervention and ongoing owner control are essential.