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New Dog In A Multiple Dog Household – Aggression

We have 3 dogs a Golden, German Shepherd Mix, and a St Bernard Mix. Last may we took on my sons Australian Shepherd while he deployed for the Airforce. Everything was going really well until about 2 weeks ago when she has started getting very aggressive towards our St Benard Mix, which we think has some Australian Shepherd in there somewhere. We have had to break up a couple scuffles, no biting a lot of feet and growling. (so far). We don’t know why she has chosen Ledi to go after. She came to us because my son’s girlfriend has a Blue Heeler that attacked her and gave her 15 stitches in the snout. Usually, the fights break out when there is excitement or play going on. Then snap dogfight. And she will also growl around the food bin when we are feeding them like she is guarding the food bin. Otherwise, she has been the best absolute joy. Just don’t understand why after since May all of the sudden aggression.


Lynn (Carrollton, Texas)

Hi Lynn,

Very few people with one dog live with that dog in a context where the dog understands who’s residing in who’s home. We companion dog owners tend to be pretty relaxed about our expectations. If asked, our dogs would describe us, great roommates. There are downsides to this in that without having a teacher:student relationship structure most dogs never really learn the sort of skills that give them the most opportunities in life.

However, add another dog to the mix, and the downside quite often becomes magnified. You may not care whether your dog has a sense of social hierarchy that reflects teacher:student but many dogs do care about precisely that sort of thing. They tend to work things out, but I’ve always found that it’s much harder on them if it’s not clear to all that they are living in your house, not the other way around. It seems to just provide them with more points of conflict when they don’t live with you in a way that they understand as my father said to me once, “Everything you see here is mine. You just get to use it.” We didn’t call it the “family car.” It was mom and dad’s car, and we just got to use it.

I use the following analogy with clients as one common reason “everything was going really well until about 2 weeks ago” and now it’s not.

If you put a Room for Rent sign up and I show up, and you decide based on an interview that I seem to be a decent chap, rent the room to me, and we really don’t interact in a manner that in small ways keeps reminding me who is living in who’s house. The following scenario might play out:

multiple dog household

Over the first few weeks, you’ll likely report to your friends, “He seems to be a good fellow. We hardly see him, and when we do, he seems decent enough.”

However, somewhat further down the road you may come home and find me raiding the fridge in my underwear.”

“Aha!”, you say to yourself, “He’s been holding back.” And, of course, you’d be correct.

The new dog in the mix didn’t show you his cards right off the bat. He wanted to get a sense of the hierarchy in his new pack and once he felt he had an accurate read on things he made his move. It might not have ever occurred to him to do this if:

  • Your own pack knew who was living in who’s home.
  • It was made clear with constant reminders to him from day one.

Which dog he targeted is likely based on “best bet.” Either due to how he assessed the dogs drive and/or physical susceptibility.

Whatever the case, things may settle down if they’re given a chance to work things out on their own but it can get messy and doesn’t always have a happy ending.

I’d recommend starting implementing some structure for all the dogs that conveyed daily, “This is my house, and you just live here.” No less loving just more understanding. My Nature’s Template book will help you navigate that path.


John ‘Ask The Dog Guy’ Wade
Embracing Science and Common Sense

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