Help! My 2 female dogs are fighting and I don't understand why.

Currently we have 5 dogs who share a 2 acre yard. We rescued a hound as a pup in Aug of 2017. We rescued a great Pyrenees as a pup in March of 2019. Both are neutered females. They have been together since. Last week in the house they had a fight. The hound ended up at the vet for $1000 in care. There was no food involved. We are keeping them separate now but I am very concerned about what happened and handling things going forward. The hound is vocal but harmless and the Pyrenees is very friendly with people and usually calm with other dogs. I have seen her go after and kill a groundhog but she has never had any other dog fights. Any advice , guidance of direction would be appreciated. We love both dogs and it's a difficult predicament.

Leerburg's Answer:

So what triggered this fight, we may never really know. That said, spaying and neutering is not a solution to behavioral problems and often does very little to prevent aggression. In Ed's experience, female-on-female dog fights are some of the worst. Once a dog fight has happened all you can really do is manage the situation. Keep the dogs separated. Consider muzzling the Pyrenees. And always keep them supervised if they are in a room or area together.

If I am doing my math right, your hound is 9 years old and the pyrenees is 7, right? Given that they haven't had any problems until now, there could be some aging pack dynamics at play. It is not unheard of for a healthy dog to attack a sick, aging, or injured packmate.

For now, I would do my best to manage and likely muzzle the Pyrenees and keep the hound safe and comfortable.

I would also recommend checking out our course on Dealing with Reactive, Dominant, & Aggressive Dogs if you want to learn more. The course heavily focuses on different types of aggression and how to manage and handle an aggressive dog.