Hi wmarine, congratulations on bringing a new family member into your home. Has Chuga met any of your other dogs yet? If not I would bring them outside to meet for the first time. Preferably, not on your property but in a neutral location. Do you have family members, or friends that can give you a hand with this?
It would be really nice if there was a way for all of the dogs to go for a good, long walk together after meeting each other for the first time. This would bring them together in a good way. It would also tire them out a bit before coming into your home together for the first time. This will help set Chuga up for success. Tired dogs listen better.
I think Chuga will likely copy whatever your other dogs do as far as the cats go. Dogs learn good and naughty behavior from each other. I would keep a close eye during the introduction. Maybe keep Chuga on a lead as a safety measure?
We once adopted (long story) an adult 3 1/2 year old German Shepherd into our home. We already had a cat, a German Shepherd mix, and a Doberman. All were females. The dobie, and German Shepherd had a couple of "disagreements" at first, but became good friends later.
Because of the way they got along at first we always kept a very close eye on everyone. When we went out we separated the German Shepherd from the Dobie and German Shepherd mix. After 2 years I realized we didn't need to do this, but it had become a habit. Eventually, all 3 dogs, and our cat came to be loving family members with each other. It took time and patience. But it was a joy to watch our girls eventually become friends.
German Shepherds are intelligent, eager to please and intuitive, among other fabulous qualities. I believe once Chuga learns the ropes he'll do well. Just keep a close eye on things. You now have a pack. You probably already know but just in case remember that praise goes a long way.
Please keep us posted on this, and if you have more questions please ask them here.
I wish you all the very best with this.
Thank you for your service.
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