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(207) 846-6515 H

(207) 846-6515




Dogs can become aggressive towards other dogs in the same household for a variety of reasons. In any single episode of aggression there are usually multiple reasons at work at the same time.

General reasons for aggression include: fearfulness, protectiveness, redirected aggression, territoriality, resource guarding, miscommunication and physical health status.

The temperament of the dogs involved is another factor: some dogs are genetically more prone to aggressive behavior; some dogs are fearful or anxious because of inadequate socialization early in life.

The particular situation matters: competition (food, toys, owner attention); excitement (greetings, running and barking in the yard), and close contact (running through a doorway to get in or out of the house) are environmental factors that increase the risk of an aggressive episode occuring.

Owners might inadvertently increase the risk of aggression: for example, if Spot has a treat and Princess comes near, Spot might appropriately growl and posture to warn Princess away. Spot and Princess’s owner might decide that this is unfair, and scold Spot, take the treat from him and give it to Princess. If his owner repeats this action a number of times, Spot will become more and more anxious when he has a treat, significantly increasing the risk of a fight when Princess comes near.

Dominance of one dog over another can be a reason for aggressive interactions, but it is probably not as important as many owners believe. When one dog is truly dominant to another dog, and both dogs have generally neutral, stable temperaments, the dominant dog is most likely to clearly communicate its dominance and the submissive dog its submission without a fight. Attributing household aggression to dominance and ignoring the other factors mentioned earlier is a misjudgement that could lead to important mistakes in attempts to treat the problem.


If the owners are present when a fight occurs they will have to make a quick decision on whether or not to break it up. In most cases it is best to intervene, but in some situations it might not be safe for an owner to do so. A loud verbal command should be used first, but if it does not work after two or three tries the owner should stop because the dog(s) might be interpreting the yelling as encouragement to fight harder.

Anticipating that a fight might happen and having some tools that can help safely break it up is a good strategy. Examples of some tools that can be used to break up a dog fight include: cans of compressed air or citronella, ultrasonic devices, a bucket of water, a garden hose, pot lids to crash together, a baby gate or peg board wedge between the combatants, leashes attached at all times, a heavy blanket, and sofa cushions.

Neutering and spaying might reduce intermale and interfemale aggression respectively.

Thoughtfully identifying situations in which an aggressive episode might occur is the most important preventive measure. Examples:

- If food is an issue feed the dogs in different parts of the house.

- Do not allow dogs to excitedly greet visitors or family members together.

- Do not allow dogs to excitedly run and bark in the yard together.

- Deny free access to highly desirable toys and treats.

Use control devices such as leashes, head halters and muzzles.

For very high risk individuals, keep the dogs in different parts of the house.

Never use physical punishment or harsh scolding. These will only serve to make the dogs more anxious and more likely to fight.

Never attempt to establish one dog as the dominant individual in a multidog household. This approach had been used by behaviorists in the past, but it has now become clear that it is very difficult to accomplish, and failed attempts can compound the problems between the dogs.

Behavior modification should be attempted if simply keeping the dogs separated is not a viable alternative. Behavior modification begins with training each dog separately to respond promptly to basic commands such as sit, stay, down, come, and leave it. Both dogs should be on a “sit for all interactions” program. It is ideal to keep the dogs physically separated for an extended time period until this training has been accomplished; not just days or a week, but one or two months would be appropriate in most circumstances.

If the dogs have been separated for training they should first be reintroduced only on walks together. When it is clear that this activity is tolerated they can then be together in the home, with owner supervision.

Every acceptable social interaction and other appropriate behavior should be reinforced with praise and/or food. Owner should continue to identify possible triggers for aggression and avoid them, prevent them, or train and reward an alternative desirable behavior.

Medication (prescribed by the owner’s veterinarian) may be useful by decreasing a dog’s general states of arousal, impulsivity and reactivity. Medication might also help dogs that are likely to fight because of mental health problems, for example, cognitive dysfunction in senior dogs.


The chance of successfully treating this problem depends largely on identifying possible causes for aggressive behavior and avoiding them or otherwise managing them. Some other factors that influence the chance of success:

- Fighting between two female dogs is often intense and seemingly unprovoked; the prognosis is fair to poor.

- Fighting between male dogs may be decreased with neutering (of both dogs); the prognosis is fair to good.

- When one or both dogs are fearful, anxious, or not well socialized the prognosis is poor; it improves to fair if there is a positive response to medication.

A sad truth is that some dogs will never be appropriate for a multidog household, even with extensive training and medication.

Yarmouth Veterinary Center



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