I think we humans overrate these "meetings" sometimes and then we go about it the wrong way as well.
Humans like face to face meetings, to shake hands, hug, kiss, whatever.
Dogs aren't like that. Face to face, eye contact, that type of thing can be threatening in a dog world
to some dogs.
It's not something I ever gave much thought to until I wound up with a dog that didn't like other dogs. Let me say that face to face dog introductions don't work well in her world.
The way we adapted was to - instead of face offs - simply walk together. At the same time, on leashes, not touching. Slowly, on your terms, the dogs get to sniff eachother while walking. (Dog does not pull you over, you allow dog to go over.) Within a few minutes, it's generally fine once the dogs realize there's no threat. Of course it's also best to do this on territory neutral to both.
With the Chi, just because of his size being so small and vulnerable, I'd probably hold him for a while on said walk. Making sure the person holding the Shepherd was firm with him and did NOT let him over to the Chi at first, just keep walking for a good amount of time. (There is a responsibility here with the Chi also and that is to also have good behavior and not antagonize the Shepherd
so I wouldn't allow that to happen either.) Once everyone's walking and behaving then I might stop or slow (in this case) and while holding the Chi let the Shepherd sniff him from behind, and if they're safe, then they could be introduced face to face, feeling out whether that would be best again by walking or perhaps by still holding. I say feeling out because it depends on how everyone's behaving. If there's snarling just keep walking and of course correct. Rinse and repeat. You have to be stong leaders with both of these dogs and not either one behave badly.
A big part of training with a German Shepherd is just helping them learn that "nothing bad is going to happen". They do have a tendency to take matters into their own hands if their leader doesn't, and that's when there can be problems. Training involves exposing them to various situations while the leader is in control and teaching them that nothing bad is going to happen. With repetition this becomes a trust issue: they trust that things will go well because they have lots of experience seeing things happen that way with you. What it boils down to is: they don't have to "act" because they know you will. Which is really why they say it's so important with this type of dog to be trained and socialized from the beginning.
But I do think that a stable tempered German Shepherd is like an open book and is ready and willing to learn anytime with the right person or people and can absolutely learn how to be a great companion. Absolutely. But I also think it's about not getting into bad habits as well, because a dog who's had no training or socialization has made his own rules and boundaries and taught himself (the plane trail story brought tears to my eyes thinking that's all he had to do out there) and you're not exactly sure what he's thinking. Now there could be a little confusion learning if things aren't clear and consistent at all times. It's all about developing communication and trust between you and the dog.
I think you have a really great opportunity to take this duckling and make him into a swan!
It's great that a trainer is coming out, and if you don't have it already, pick up or order a copy of Good Owners, Great Dogs by Brian Kilcommons and Sarah Wilson. They also have other books and I believe one is about adopting dogs from a shelter.
As for the introduction with your son, the walking method also works great for that as well. It is very common for children to be a little intimidated with a dog of this size and stature. On the walk, have your son bring a tennis or soccer ball. When he is comfortable, let him start throwing it for the dog. The dog will quickly learn that this is a fun game with him. And take it from there. Your son will probably still be anxious so make sure dog doesn't inadvertently knock him over (that happened to us once with our neice and it literally knocked the wind out of her) but continue the games in your yard and get him holding the leash, etc.
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