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HomeVeterinary Behavior ArticlesCanine Aggression: Sibling Rivalry

Veterinary Behavior Articles

Canine Aggression: Sibling Rivalry

What is a dominance hierarchy and why is it important to dogs?

Dogs are social animals whose evolutionary history makes them willing and able to live in groups. Group living enabled wolves to work together to obtain food, raise their young and defend their territory. It would be counter-productive for members of a group to fight with each other and risk injury. That would prevent them from working with the group. Although domestic dogs are not wolves, they do have a social structure in which each dog is either dominant (leader) or subordinate in its relationship with each pack member. This is a “dominance hierarchy”. The leader or “alpha” dog is the one that has first access to all the “critical” resources. These resources include food, resting places, mates, territory and favored possessions. Assertion of dominance by the alpha is generally communicated through facial expressions, body postures and actions. Fighting is rare, since as soon as the subordinate submits or defers to the alpha animal and the alpha gets its way, he or she gives up the challenge.

My dogs have lived together for some time and now they are fighting. Why?

Fights between dogs in the household are often about dominance or social status. Social status aggression most often occurs when dogs reach social maturity at 12-36 months of age. Fights will be about those resources that are considered important to dogs. Therefore fights may occur over treats, owner attention, greeting the owner upon return, sleeping positions near the owner, entering or exiting the home, high arousal situations such as fence running, or movement through tight spaces. These fights occur most often between dogs of near equal status and often, but not always, dogs of the same sex, and seem to be most severe between female dogs.

I try to treat my dogs equally, but they still fight. What am I doing wrong?

Trying to treat two dogs as equals will only serve to counter the natural tendency toward a hierarchy. The dog that is the more dominant in a relationship needs to be supported in its position and the more subordinate must be taught to accept the relationship. When you support or encourage the subordinate dog as it tries to gain access to resources such as your attention, the dominant dog may begin to challenge and fight, in an effort to keep the lower ranking dog in its “ place”. If you then discipline the dominant dog, or pull the dominant dog away, you have favored, supported and come to the aid of the subordinate dog.

Both my dogs are the same age, and after a third, older dog died, they began to fight — why?

Conflicts may occur between dogs when the dominance status is ambiguous or when they are particularly close in rank. After the decline, illness or death of an older dog, fighting may begin in the remaining dogs even when one is clearly dominant. This is because the older dog may have been dominant to both dogs, and now they are trying to establish new positions. In any case the fighting can be severe and injurious. Although you should generally attempt to allow dogs to resolve their differences on their own you will need to intervene if there is the potential for injury. Under no circumstances should the dogs be allowed to "fight it out". You could be injured due to redirected aggressive attacks, or when you attempt to break up the fight (see below).

My younger dog always deferred to the older dog, but now they fight.

One scenario that can result in social aggression is when an older, previously dominant dog, is challenged by a younger, more domineering dog. This may happen as the older dog ages, or as the younger dog reaches behavioral maturity at 12 to 36 months. This may be an attempt to alter the existing hierarchy but at other times the dog is being a “bully”. Sometimes the older dog will acquiesce and things are fine but at other times the owners do not want the change and intervene. In some situations, the older dog will not relinquish the dominant role even though it cannot physically compete with the younger dog. This can result in severe, injurious fights.

How should I break up fighting if it occurs?

This can be a dangerous situation for people and dogs alike. Owners usually try to reach for the collar of the fighting dogs, or if one is small, pick it up. This can result in severe owner injury if the fighting is very intense. If both are wearing leashes they can usually be pulled apart. If all else fails, you might be able to break up the fight with a water rifle, citronella spray, broom or another distraction (such as pepper spray or a fire extinguisher). Reaching for the dog is usually the worst thing to do, as you could be injured (either accidentally or intentionally).

When people intervene in dog fights, redirected aggression is possible. Aggression (growl, snarl or bite) can be redirected to a person, animal or object other than that which evoked the aggression. If during the course of a dog fight, you pick up one of the dogs, the other may continue to attack and direct it at you.

What should I do when one of my dogs challenges another?

Aggression between household dogs can be difficult to treat. You will need to identify the subordinate dog, and ensure that you are not encouraging the subordinate dog to challenge the more dominant. It is critical that you never come to the aid of the subordinate against the more dominant. If left alone, the dogs will often use posturing and threats to end encounters without injury. If one dog backs down, the problem may be resolved. However, when neither dog is willing to give up the dominant position (as in a young dog challenging an older dog in the home), fighting will usually result.

A common owner error is the desire to make life "fair". This often results in owners allowing subordinate dogs access to resources, such as attention, treats, toys, or entry into territory that they would not normally have. Usually the subordinate dog would not behave in a manner that would challenge the dominant when no one is around to “protect” it. If you encourage or protect the subordinate dog, it may be “tempted” to break the “rules”, and the dominant dog may become aggressive to enforce the “rules”. If you then punish the dominant dog for aggression, the subordinate dog learns it can engage in prohibited behavior while the owner is present. This is why, in many households, there is no fighting when the owners are gone. The subordinate is aware of the hierarchy, and does nothing to challenge the dominant dog, unless the owners are around to intervene.

Another potential problem may occur when the relationship between individuals is context dependent. In other words, one dog may be dominant about owner attention but may not care who eats first. This is why it is important to understand the entire social relationship between dogs.

How can I treat this problem?

Although the dominance relationship between the two dogs must be dealt with, the first step is for the owner to gain complete control over both dogs. As leader or alpha your presence and commands should be sufficient to prevent all dominance challenges between dogs and to intervene as needed when threats emerge. Control of each dog is achieved through the use of verbal commands, by leaving a leash and head halter attached for immediate control, and by withholding all rewards unless earned. Attention on demand not only encourages situations where one dog may challenge the other, but also allows your dogs to control you. Inattention on demand teaches the dogs that all rewards are provided only when you choose, and reduces or eliminates those situations where challenges might occur. Head halter with leash control and obedience-reward based training of each dog should first be done separately. With a head halter and remote leash on each dog you will have effective control, and a means of controlling and separating the dogs if needed. With control of the head and mouth, aggressive threats can be curtailed and either dog can be placed in a subordinate posture, by pulling up on the leash, closing the mouth, looking the dog in the eyes, or pulling the head sideways so that the dog’s gaze is averted. In severe cases muzzles may be needed to keep people and dogs safe while therapy is undertaken.

Next, treatment must be designed to identify and support the dominant dog. Several differing treatment plans exist. One is supporting the dog that has been in the household the longest, usually this is the oldest dog. Another treatment is to identify the dominant dog based on how the dogs interact, in other words, who threatens and who defers. Care must be exercised to watch for bullies who do not allow other dogs any status and are not consistent in the application of threats and response to deference. All dogs must have some status and the ability to respond in an appropriate manner and thus avoid aggression. In some cases the dog that is chosen is the younger, larger, more physically capable dog, if this dog wishes to be the leader. Often, this is also the aggressor. You must allow the dominant dog priority to go outside, to come in, or to receive food or owner attention and affection. If you are petting the dominant dog and the subordinate dog approaches, make it wait. Importantly, you must avoid all circumstances that elicit aggression. If the more dominant dog approaches or challenges the subordinate dog and the subordinate dog assumes a subordinate posture, the owners are not to intervene as long as the dominant dogs stop. If the dogs are likely to fight when you are away or at homecomings, separate the dogs whenever you are out, or are not available to supervise.

On other occasions, neither dog is willing to be subordinate. This could be due to a challenge to the hierarchy as a younger dog matures, as an older dog becomes sick or aged, when a new dog is introduced into the home, or when one dog is not clearly dominant to the other. You should learn how to recognize canine body language and low-level threats such as eye contact, snarls or low growls. Keep records of threats, attacks, or tension-producing situations. An owner must have excellent control over both dogs in order to succeed. To facilitate treatment, decrease the chances of injuries and increase owner control, a remote leash can be left attached to one or both dogs. Often the best form of owner control is to fit and train each dog with a head halter, and to leave a leash and head halter on each dog when they are together (under the owner’s supervision). In other cases, basket muzzles may provide more safety and allow owners to work with the dogs.

Once you have gained sufficient control over both dogs, and have identified the more dominant, you will need to deal with the circumstances that might elicit aggression. Greetings should be low key, and both dogs should be ignored. Treats are avoided and rawhides or other delicious things are not given unless the dogs are separated or on leash. Movement through tight spaces is avoided or controlled. You must be present to ensure that the dominant dog gains preferential access to food, resting places, territory, owner attention and treats. Commands and rewards or the leash and halter can be used to ensure that the subordinate does not challenge, and that the dominant does not continue to show aggression once the subordinate submits. Getting the dogs together without incident can best be accomplished when the dogs are otherwise occupied and when a confrontation is unlikely, such as during walks or feeding. It is usually best to have two individuals to walk the dogs (each person controls one dog) and not to allow them to forge in front of one another. During feeding, keep the dogs at a distance, far enough apart that they do not show aggression. Slowly the dishes are moved closer together as long as the dogs do not react. The food serves as a reward in this situation. If the dogs react, the food bowls are moved further apart. When the owner is not home or supervising the dogs, the dogs are separated or crated.

Basket muzzles could be left on each dog to increase safety while the dogs are together. They can also be used to “proof” the training, by putting the dogs together in situations that previously led to aggression. Drug therapy for one or both dogs may also be useful.

Can social aggression always be corrected?

At times aggression may persist despite owner control and intervention. In those cases alternate living arrangements for one of the animals may need to be made.

This client information sheet is based on material written by Debra Horwitz, DVM, DACVB and Gary Landsberg, DVM, DACVB. © Copyright 2002 Lifelearn Inc. Used with permission under license. January 26, 2018.

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