When familiar dogs suddenly fight
One of the most distressing problems in a multi-dog household: two dogs who lived peacefully for months or years start showing tension or fighting outright. There is almost always an identifiable cause.
Most common causes
1. Hormonal change
An adolescent female coming into season, a male reaching sexual maturity (18-24 months). Hormones activate competition that wasn't there before.
2. Health and pain
One dog begins to suffer pain (arthritis, dental issue, chronic ear infection). The painful dog becomes irritable, the other reacts. Always a vet check first when new conflicts appear.
3. Hierarchy shift
A junior maturing and "moving up". A senior who no longer wants to be "first". Natural renegotiations.
4. New stressors
Moving house, baby, building work, routine changes. Dogs offload stress onto each other.
5. Human mistakes
- Rewarding the "stronger" dog with attention after a scuffle.
- Punishing the "weaker" dog.
- Food, attention or treats without order.
- Physically intervening in fights instead of preventing them.
6-week management plan
Weeks 1-2: separation and diagnosis
- Full physical separation for 1-2 weeks (no visual contact, no shared spaces). Brings down immediate tension.
- Vet check on both: pain, thyroid, neurological exam.
- Identify trigger: food? toy? human? location?
Weeks 3-4: gradual reintroduction
- Daily parallel walks — start at 5 m, close the gap.
- Supervised time in neutral spaces (garden, hallway with barriers).
- Not yet together indoors.
- Massive positive reinforcement when they ignore each other or are polite.
Weeks 5-6: controlled dynamics
- Indoor reintroduction with visual barriers if needed.
- Permanently separate feeding.
- Human attention shared with order.
- No high-value resources freely available.
When re-homing is kinder
Hard but sometimes necessary:
- Fights with serious injury more than 3 times in 6 months.
- One dog bullies the other relentlessly.
- Multiple irreversible factors (two intact adult bitches, both territorial).
- Behaviourist recommends separation after 6+ months of work with no improvement.
Not a failure. A responsibility — both dogs' welfare matters.
How CanAI helps
Each dog has its own profile — individual health history is critical for spotting hidden pain. Ask the AI chat about your specific dynamic. And your insurance should cover vet bills for both dogs: a serious fight can mean £300-1,000 of wound care.