So you're wondering how to introduce a puppy to an older dog. First of all—congratulations on getting a new puppy!
There are some things to consider when introducing a puppy to an older dog, whether it's another breed or also an Australian Shepherd. You are not just introducing them to each other but to the home and all of the dynamics that entails. Actually, it's not recommended to even introduce them in your home as older dog could become territorial. So it's best to start introductions in a neutral place like a nearby park. It's best if it's within short walking distance to your home though.
When introducing them to each other at the park be sure to be calm and not pull on the leash. If you have a friend or family member to control the puppy while you have the older dog on the leash so much the better. After the initial greeting on leash if the park allows you can let them off-leash so they can decide for themselves whether to play or ignore each other. If the puppy wants to play but the older dog doesn't she can then move away and not feel boxed in.
Debra J. Alder
When you introduce a puppy to an older dog this is the kind of result you want. :)
This summer, we added Daisy to our family. She is 3 months old in this picture and as you can see, she is learning all the right behaviors from Skyler. He is patient and kind, she is a very good student, very social and so cute!
The reason I suggest choosing a neutral place to introduce a puppy to an older dog that is within close walking distance is primarily so you don't have to put them into confined, close quarters like a car so soon after meeting. You don't want it to be too far either for the puppy to walk (especially on cement sidewalks).
Once back at home you can start by letting them continue to socialize in the yard. Don't leave them unattended and intervene if you see any aggressive or dominant behavior. You want to nip this in the bud so it doesn't establish itself as a dynamic for their relationship.
What else to consider? Before introducing a new puppy to your home you will want to remove any toys, food bowls, bones and even beds that the older dog might become possessive over. Don't forget to check the yard for things like this as you don't want to invite a fight in your yard as soon as they get home from the park.
The main thing is to reassure the older dog that he is not being put in second place. You don't want the puppy to represent a threat to the older dog's position, food and goodies or your attention. For example, when letting them in from the yard take the older dog's leash off first.
You will also want to feed the older dog first and still have one-on-one time alone with him so he doesn't feel he's missing out on your attention. At first keep their food bowls well apart and make sure they aren't taking each other's food. Don't put them in confined spaces together or leave them together unattended for at least the first couple of weeks. I know that can't be avoided sometimes but ideally you will want to makes sure their interactions are positive. Some say to let dogs "work it out" and allow the dominant one to assert control. To a certain extent that is true but when it turns aggressive and nasty you have to be the ultimate pack leader and intervene.
Puppies have a lot of energy and can be a nuisance for older dogs. If you see that the older dog is getting frustrated by a rambunctious puppy you will want to separate them. Since you will also want to spend time alone with the puppy, so you can also bond, you can use this opportunity to exercise the puppy to tire it out a bit.
Basically, the idea is to introduce them slowly while minimizing the opportunity for and triggers of aggression. You are the leader and you have to set the tone.