Let me preface this post by stating I should have done more research about the breed beforehand.
A few months ago I rescued a 2 year old Australian Shepherd. I was bringing her into a home with a 7 year old Standard Poodle, 7 year old Goldendoodle, and 2 year old Cavapoo. The Poodle and Goldendoodle are half brothers with the same father.
Here's a picture for reference...
At first, as expected, it took a few weeks for the Aussie to get comfortable in the new household. After 2-3 weeks of adjusting, it seemed that she was a perfect fit. She is very affectionate to myself and my parents, and even plays with the other dogs from time to time.
However, over the past three months, she has gotten into 3-4 altercations with the other dogs. By altercations I mean lunging/biting at the other dogs with no signs of stopping. We end up having to grab her neck and physically pull her off the other dogs. Then we put her on a leash and bring her outside to cool down. After about 10-15 minutes, we let her back in the house and it's as if nothing happened.
Here are my observations from each altercation...
1) The first time it happened my mom had just brought her back from walking around the area for an hour or so. She was in the backyard with her, and obviously was panting heavily. My dad then lets the Goldendoodle into the yard, and being excited to see my mom, runs over to her at full speed. I don't want to make excuses for the Goldendoodle, but he's a big goofball in that he can be clumsy and knock into people. Obviously it isn't intentional, however he ran at them full speed and ended up crashing into the Aussie. She immediately lunged at him and started to attack. My dad ended up having to pull her off of the Goldendoodle and separated them until she could calm down.
2) The second time it happened was when my mom came home from being out. About five minutes prior to my mom coming home, a delivery driver dropped off a package and the Aussie was going crazy barking at him/her until they left. We actually had 1-2 occurrences where the delivery driver was getting back into his truck and when we went to open the door to get the package she would run out at full speed and chase the truck down the street. Miraculously both times I guess when she thought the truck driver was long gone and no longer a threat, she came back to the house on her own accord which left all of us puzzled and baffled. Anyway, she was already hyped up from the delivery driver when my mom comes home. The Poodle and Goldendoodle run to greet my mom in excitement and accidentally bump into the Aussie. She immediately lunges at the Goldendoodle again and attacks him relentlessly. This time I had to pull her off by the neck and put her outside to cool down.
3) The third time is a little different from the first two times that perhaps can be attributed to the dogs bumping into her when she's in an excited state. She was laying down by our screen door which overlooks the backyard. She appeared to be in a relaxed state when all of a sudden my sister's Cavapoo comes up to the screen door and starts to jump on it. The Cavapoo was clearly excited to see us and was just saying hi, however the Aussie immediately started to growl and get nasty. She then jumped on the screen door and unfortunately since it wasn't completely locked managed to open it and get outside. She then bit the Cavapoo and practically had her in her mouth since she's really small and only weighs about 20 pounds. My dad had to grab her by the neck until she released the Cavapoo and separated them to calm her down.
There was another time when she fought with the Standard Poodle, but none of us were nearby at the time so we're not sure what caused that fight to occur. We've tried to socialize her with other people, but she clearly doesn't like strangers.
When my uncle came over my dad brought him and the Aussie in the backyard to introduce them. At first she would bark at him, but we told him to keep his hands in his pockets and not make eye contact. Eventually she stopped barking and started to smell him. Then all of a sudden she jumped on him and was staring directly at him almost daring him to look at her back as a challenge. My uncle didn't want to continue further which I can't say I blame him so we separated them and kept her outside while he was in the house.
From the research I've done on Australian Shepherds, it appears that this kind of behavior is not uncommon and is due to to the fact that they are a working breed and are very protective. All of the dogs I've owned my entire life are breeds that tend to be mild mannered and have a high tolerance threshold. It appears that she has a very low threshold and has no problem letting other dogs/strangers know that.
Ultimately we want her to be more sociable with dogs/people, but we're not sure exactly where to start as we've never had to train any of our dogs before. I have a feeling that the behavior of the other dogs will need to be adjusted as well. Any advice that can be given would be much appreciated. I would hate to have to resort to crating her or keeping her outside whenever we have company. At the same time, I can't keep waiting until she ends up seriously injuring one of our other dogs, or God forbid another person.