Small animal kills

Question
My aussie is very territorial.  She has killed a cat, possum, rabbit, groundhogs, birds, mice, moles that come into the yard.  She doesn't seem to mind stray dogs (med size) that comes into the yard too much.  She does not like strangers and takes a long time to trust new people.  My question is - does she know not to kill a puppy or small dog if one comes into the yard or if I get one? Do dogs know their own species?  I would hate to think she would kill a neighbors small dog if it came into the yard.  Otherwise, she is the sweetest, loving dog!

Answer
Dogs do know their own species if they have been at all socialized, such as in puppy class, but some dogs are still territorial enough to attack a strange dog that comes into their yard.  If she doesn't mind local stray dogs, yet kills other species, perhaps she is more predatory than territorial.  Aggression toward people and aggression toward dogs are separate issues and being one does not imply that a dog is the other.  If you are planning to get another dog, the safest thing, in my opinion, is to get a pup of opposite gender and introduce them on neutral territory, not at your house, and in carefully controlled circumstances.  With dogs that have killed anything, I recommend that you get an experienced trainer or behaviorist to evaluate your dog's ability to live with another dog.