Introducing a new puppy

Question
Hi Jill, Awesome site!! Ok, I have a 13 month old male lab/poodle mix (shelter dog - neutered) that I have had for one year and his name is Bosco. Great dog, shy, submissive nature, very protective of house. Last week, I adopted a poodle/schnauzer mix female - spayed about 8 months old...Lucy. She is still a little high strung, but she is very dominant. She constantly is going after Bosco for play and he plays along pretty well, but I noticed he seems to be more on the defensive. At times, when they get going, I will hear her growl...at all times, during play, she is biting at his neck and at his heels. I am not sure if I should be correcting this. I am afraid the male, Bosco is somewhat terrified - even though he is twice her size. When i am petting her belly, he is very interested in sniffing her and she was ill when I first brought her home, he brought her a toy (which is very strage - but cute). I want it to be a happy environment for both dogs and I feel the male is afraid all the time...what if anything should I do to help encourage a "fear" free environment.

Answer
It's impossible for me to determine if Bosco is afraid of Lucy.  A growl does not mean fear or dangerous aggression, it can be a warning that one dog very well understands from another or a simple play related vocalization.  It's very unlikely that a puppy Lucy's age would be seriously attempting dominance aggression toward an older dog.  Her biting at his neck and heels is a control play behavior that is very common between dogs (just observe any dog park.)  Your description of Bosco as a "shy, submissive, but very protective of the house" indicates his "protection" of your house is fear based, but this has nothing to do with his interaction with Lucy.  What I suggest for this situation is that you establish some psychological rank over Lucy by introducing positive reinforcement training, ONE behavior at a time.  Karen Pryor's web site provides information as well as Patricia McConnell Ph.D.'s book on the topic (and she also has a book on multiple dog households.)  Lucy should obtain at least one behavior she can successfully offer 100% of the time on your command for reward/praise and be made to offer this behavior for all important interactions with you (being fed, being petted.)  It will take a few weeks to create this behavior. Meanwhile, observe play interaction between Bosco and Lucy.  Do not tolerate any interaction that produces a visible fear response in Bosco (as in, running away, real obvious fear response.) IF YOU DO NOT LIKE what you are seeing (in terms of Bosco's response), get in the middle of it, give a growly "NAH!", and give both dogs something else to do (use play objects, one for each dog.)  I say this with hesitancy since it depends upon your perception; Bosco should be able to take care of himself, and I suspect he is. Lucy's growling may be play related.  The entire scenario between them might be totally normal.  The key element in judging this is observing Bosco.  If he is quickly extricating himself and hiding, and/or obviously avoiding Lucy, you need to act.  Otherwise, let them work it out.