We have a 3 year old male black labrador and have just gotten a 8 week old female black labrador, but the older one is quite aggressive at the sight of her.

So we have a 3 year old male black labrador called Max who was a rescue dog who also didn't socialise much when he was younger. We got have at the age of 1 and whilst he's super gentle and trusting quickly with humans, he tends to bark and chase other dogs, birds etc.

We have a cat who he's become accustomed to over time, so we figured he would adjust just as well with a baby sister, but he's heavily aggressive around her, barks loudly, foams at the mouth, whimpers and jots around.

I assume this is normal. We're opting to keep then separated most of the time, with Max being able to roam freely around the house and maintain his routine, whilst the puppy, Minnie, is kept in our bedroom with supervision in her own space. We have a overly large cage for her, mainly for sleeping in at night, but also as a way to slowly introduce her to Max, and we are considering putting up some pet gates by the bedroom so he can see her, but also have the option to go away and come back in his own time.

I'm hoping by sharing this here that you might be able to offer some advice or pointers as to what has worked for you with similar situations, or with dogs who are equally unsociable or territorial.

Is this normal? Any advice for getting the larger dog to be more calm around seeing the puppy in the house?