When Your Dogs Don’t Get Along

A Compassionate Guide to Household Dog Aggression

Important Disclaimer: This article is for educational purposes only and is designed to help you understand household dog aggression and implement immediate safety measures. It is not intended to diagnose your dogs’ specific situation or replace professional veterinary and behavioral evaluation. Every case of inter-dog aggression is unique and requires individualized assessment and treatment by qualified professionals. If your dogs are fighting, please seek help from your veterinarian and a certified behavior professional as soon as possible.

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If you’re reading this, you’re likely experiencing one of the most stressful situations a dog owner can face: your dogs are fighting. You might be feeling scared, guilty, exhausted, or heartbroken. Please know that you’re not alone, and seeking help is the right thing to do.

You’re Not Failing—This Is More Common Than You Think

Household dog aggression (also called inter-dog or housemate aggression) is more common than most people realize. Many owners treat wounds at home and never report incidents, suffering in silence. But here’s what you need to know: without intervention, aggressive behavior typically escalates, resulting in more serious injuries over time.

This isn’t about being a bad owner. This is a complex behavioral problem that requires professional help—and there is help available.

Photo by Yuriy Vertikov on Unsplash

Understanding What’s Happening

Why Dogs Who Once Got Along Start Fighting

True inter-dog aggression often emerges between household dogs who previously coexisted peacefully. The most common pattern occurs when a younger dog reaches social maturity (typically between 1-3 years of age), and behavioral changes create conflict with an older housemate who struggles to adapt to the shifting dynamics.

Think of it this way: your younger dog is going through the canine equivalent of adolescence into adulthood, and the established social relationship between your dogs is being renegotiated—often in ways neither dog knows how to handle appropriately.

Common Triggers and Risk Factors

Medical Issues: Pain or underlying health conditions can cause or worsen aggression. A dog who hurts may lash out defensively, or discomfort may lower their tolerance for normal dog interactions.

Anxiety and Fear: Some dogs struggle to properly assess social situations or feel chronically anxious, leading to defensive or preemptive aggression.

Resource Guarding: Disputes over food, toys, furniture, doorways, or even your attention are involved in nearly 73% of household dog aggression cases. Even in homes with plenty of resources, instinct to guard valued items can trigger conflict.

Environmental Stressors: Changes like moving, new family members, schedule disruptions, or even one dog going through social maturity can destabilize previously peaceful relationships.

Higher Risk Factors:

• Same-sex pairs (particularly female-female pairs) are more prone to serious conflict and poorer outcomes

• History of skin-breaking bites or aggression that occurs on sight indicates higher risk

• Unprovoked attacks (with no identifiable trigger) are associated with poorer prognosis

• The aggressor being younger and heavier than the victim is a common pattern

Understanding Your Dogs’ Roles

Not all aggressive displays are the same. You may have:

An Offensive Aggressor: The dog who initiates conflict, stares, stalks, blocks access, or controls space and resources.

A Defensive Victim: The dog who fights back out of fear or self-protection, showing defensive body language before escalating.

A Mediator Dog (if you have three or more dogs): This dog watches interactions carefully, often accompanies and protects the victim dog, physically comes between the aggressor and victim, or blocks the aggressor’s view or access to the victim.