Why would a dog fight with a familiar dog who lives in the same home?
Dogs are complex social animals. While their wolf ancestors lived in social groups with other wolves, the wolves were related in most cases, typically born into the group, and a familiar structure developed. In contrast, dogs that share a household are largely unrelated and are usually introduced well after birth. They must learn to communicate successfully to remain comfortable together.
While dogs routinely use body language to defuse tension and avoid physical conflict, different dog breeds vary in their ability to communicate and may not always speak the same language. Add to that the fact that humans are also part of the social group, adding an entirely different language and sometimes inadvertently interfering with or misinterpreting the dogs’ conversations. Subtle dog postures that indicate discomfort, fear, or even aggression may be overlooked and conflict can escalate, sometimes seemingly “out of nowhere.”
In addition to having a range of communication skills, dogs have unique personalities that are partly determined by their genetic makeup. People try to choose a dog whose personality and breed suit their own personalities and lifestyles. Unfortunately, when a second (or third) dog is introduced to a household, that dog’s personality may not always suit the personality of the resident dog.
Sometimes, the two dogs live together and rarely interact, but do not necessarily fight. Other times, the dogs may exhibit more obvious and severe aggression, particularly if subtle communications have been repeatedly ignored. Unlike their wolf ancestors, who could leave a group where they were not welcome, dogs are bound by their home’s walls, and aggressive conflicts can quickly escalate.
Why did my dogs suddenly start fighting?
Sometimes, it seems like fighting begins out of the blue – and that may be the case. There are several potential reasons that fighting may start.
Overlooked communication. Dogs often signal so subtly that, unless you are a trained behaviorist, early messages may be overlooked until a physical fight. Signaling is even more difficult for dogs with certain physical attributes. For example, dogs with large, prominent eyes always appear to be staring; dogs with short faces may not be able to snarl effectively.
When you do not appreciate a dog’s subtle signals, there is no opportunity for you to intervene early and prevent escalation. In any relationship, communication is critical. If the signal recipient does not behave as expected, or if the sender’s message is perceived as a threat, there can be frustration, which can progress to physically overt aggression, such as growling, snapping, or biting. For example, maybe one of your dogs approaches your other dog and stares – but then walks away, with neither dog growling. In this case, the dogs are resolving their conflict, but they may also benefit from some expert guidance to avoid escalation.
Sometimes, there is no subtle communication, and physical aggression begins relatively suddenly. Regardless of which dog appears to be the aggressor, both dogs should undergo a thorough physical and behavioral assessment to determine whether any concurrent conditions may be affecting their interactions.
Maturing socially. Aggression between household dogs often begins when the younger dog begins to mature socially, somewhere between one and three years of age. From an evolutionary standpoint, a young, maturing dog can represent a social threat and reduce an older dog’s access to valuable resources. In the home, even with plenty of resources, some older dogs exhibit an aggressive response in anticipation of this perceived threat.
Alternatively, as dogs mature socially, their personality traits become more evident. Underlying fear, anxiety, and frustration can escalate at social maturity, with the potential for aggressive responses to triggers such as access to resources.
Medical condition. An underlying medical condition can create an aggressive response from either the dog with the medical condition or the housemate. If you suddenly notice your dogs are growling, snapping, or biting, the first step is to have them both examined by your veterinarian. Pain, inflamed skin, loss of mobility, loss of ability to digest food, and loss of vision or hearing are among the many physical changes that can lead to aggressive responses.
Environmental change. A change in the environment could trigger a sudden onset of aggression, even if it seems unrelated to the dogs. For example, construction or a house guest may limit access to a favorite resting place, which leads to restlessness or competition while finding a new, cozy spot. If one of your dogs is excited when people or dogs pass by the house, then access to a new window could trigger an aggressive, redirected response toward the other dog.
Changes in routine. Increased exposure to a fear-inducing stimulus such as thunder, as well as any change in their routine or schedule can affect the way dogs interact. Try to think of any changes that occurred that may have contributed to an aggressive response. Helping your dog tolerate triggers will be necessary for successfully mending the relationship between the dogs.
Could my dogs be fighting because of a dominance struggle?
The concept of dominance in a relationship is complicated and is not often a helpful construct when trying to keep harmony in the home. A dominance hierarchy creates predictability and prevents the need for physical confrontation. In most cases, if there is a hierarchy, it is organized quietly, without physical fighting. Many household dogs do not establish a clear hierarchy.
If your dogs are fighting, a veterinary behaviorist can determine whether the aggression relates to a failed attempt to form and maintain a dominance hierarchy and can treat the behavior accordingly. In most cases, they will discover another reason for the aggression.
What are the common triggers for a fight?
There are some common triggers for fights among dogs in the home.
- Dogs often fight over access to a resource that is perceived to be valuable, such as a favorite bone or toy, a special person, a resting space, or even a dog food bowl. Aggressive behavior in these contexts is referred to as social-conflict-related, resource-based, possessive, or food-based aggression.
- Some dogs fight when moving through a narrow doorway, when contained within a tight space, or during rough play. This aggression may be excitement-related or can be related to frustration or fear.
- Some dogs become frustrated and behave aggressively toward a housemate dog when they cannot access the actual source or target of their fear or frustration, such as a person or animal viewed through the window. This behavior is known as redirected aggression.
It is important to identify as many triggering stimuli or contexts as possible. Watch for subtle signs of aggressive communication in the presence of these stimuli, even if there has never been an overt fight. Some trigger situations must be managed carefully for safety during treatment and possibly in the long term.
Sometimes, it can be challenging to identify a trigger. Do your best to describe the contexts in which your dogs have exhibited aggression toward each other. A complete medical and behavioral assessment will be critical if no trigger is found.
Are there common medical conditions that can trigger fighting?
When dogs age or become ill, their relationship with other household dogs may change. A dog that is ill may respond differently when faced with certain stimuli. For example, medical conditions that lead to pain and loss of mobility may cause a dog to become aggressive when approached. Aging dogs often experience a change in their hearing and may bark more often, possibly startling the younger dog and triggering an aggressive response. Effectively, the older dog’s behavior is no longer predictable to the housemate.
Some physical conditions, such as dermatitis, ear infections, and anal sac infections can alter a dog’s odor and pheromone secretions. These changes can trigger an aggressive response in the housemate dog. Though many dogs readily adapt to changes in how their companion dog looks, smells, or moves, other dogs may become anxious and respond aggressively.
How can I figure out why my dogs have been fighting?
Managing the relationship between two dogs is complicated. Both dogs need complete medical and behavioral assessments to treat underlying conditions. Your veterinarian can begin the work-up. Once some basic testing has been done, a veterinary behaviorist or skilled behavior consultant should continue the evaluation.
