Toy and Food Possession/Aggression

Question
Hello! I have just introduced a new puppy into my family. She is a 9 month old Norwegian Terrier/Chihuahua mix. She is spayed and I've noticed a behavior problem that I don't know how--or if--I should try to intervene and correct. I introduced her to my 10 year old male Shih Tzu (also neutered) by walking them together and introducing them in our large backyard.

During the first day, both dogs were receptive and friendly towards each other. My male dog was practically on top of the puppy all day and tried to play with her constantly. However, by the second evening I noticed that the puppy started having aggression issues towards my older dog. When my male dog is trying to play--nicely, and by himself or with me--with toys that are "his", she runs up and takes the toy while growling and snapping at him. She takes the toys and hides with them in her crate or under my couch.

Even toys are I've given her to play with--that I don't allow my male dog to touch--she becomes territorial and won't even let him walk by her crate/couch without snapping or growling at him. I don't know how to correct this, as she exhibits similar behavior over food.

I was told to hand feed her for the next two weeks, and I've been doing so. And I've also heard that I should let her 'settle in' before starting to correct any behavior, but I'm not sure I want this to continue any longer. I can't play with either dog while the other is around and that means that I have to put one of them away when I want to have play time with one of them.

Also, at the end of play time I have been taking away all the toys and putting them out of reach, so as not to cause any fights when I am not there to supervise.

Answer
Dogs are territorial and protective of their "stuff" by nature - especially against other dogs.  However, it does sound like this little pup is taking it to the extreme.  Have you seen any signs at all that she guards her things from YOU?  That would be my main concern right now.

Dogs should always be fed separately in their own space.  I'm not sure how hand feeding would help dog/dog resource guarding.  (If she is guarding her food from you, then yes, I would agree with that recommendation).  Keep them apart for all meals.  

Please read this great article that addresses this issue and gives good, practical advice on what to do:  http://www.whole-dog-journal.com/issues/14_10/features/Resource-Guarding-Behavio

Start obedience training with the new dog right away.  She needs to learn a recall so you can always call her away from a situation.  She needs to learn only polite behavior gets her what she wants. It's important that it be a positive training experience.  Look for a clicker training class or a trainer that uses positive reinforcement and humane methods. Here's where to find good training in your area:

http://www.karenpryoracademy.com/find-a-trainer
http://positively.com/dog-training/trainersearch/
http://www.ccpdt.org/
http://www.apdt.com/petowners/ts/default.aspx
http://iaabc.org/consultants

While it's possible that this behavior may improve as she becomes more comfortable and settles in, I wouldn't bet on it.  Usually new dogs won't exhibit these types of behaviors for 2-3 weeks - after the honeymoon period is over.  Please keep your old dog's mental health in mind as you decide what to do in this situation.  He's probably going to become very cautious about walking into a room - "where is she?", "is she going to snap at me?", "am I safe?"  Implement the ideas suggested in the article and give her the opportunity to learn how to behave politely.  

Please respond with any comments or further questions or if you need clarification on anything I've suggested.  Good luck!