shi-tzu behavior

Question
We rescued a 9 yr old shi-tzu from a shelter.  We already had an 11 yr old rescued cocker spaniel who happens to be deaf and submissive by nature.  We also think the shi-tzu suffers from hearing loss.  The shi-tzu will growl and snap at the cocker spaniel.  It doesn't happen all the time. We can't figure out if it is fear or dominance.  If I pet them at the same time she is fine. When I walk them together she is fine. If she is sitting down and the cocker spaniel is in the room she begins to growl. If he gets to close she will snap at him.  Any suggestions?

Answer
    Before anything else, I would advise you have your veterinarian check your Shih-Tzu's hearing to determine how much hearing loss she has, if any. Sometimes medical problems can cause or contribute to these behavioral issues. For example, she might be more easily startled because she can't hear her surroundings well, which could possibly cause her to be more apprehensive about things. If you do find out she has a hearing problem, contact a qualified trainer in your area who has experience working with hearing impaired dogs.
    In general, problems like this can often develop when a new pet is brought home. The dogs will redefine territories and test each others boundaries, and both dogs will be having to make big adjustments to their routines. Your dog's need guidance, especially now. If they don't have clear boundaries set they will try to establish their own rules, often with undesirable results.
    I use reward based training methods with great success to modify behavior. There are 3 main points to consider when modifying behavior:

1. Rewarded behaviors will increase, unrewarded behaviors will decrease. When a behavior starts increasing in frequency, the dog is somehow being rewarded for the behavior.
2. It is often much easier (for owner and dog!) and more effective to teach the dog something TO do, instead of something not to do. I always give the dog a way to do something right.
3. If the dog isn't responding, you are generally either expecting too much too fast or not being clear enough with your rules and expectations. (of course in your case, hearing loss can contribute to this also, so keep that in mind.)

    So, first of all I would build on your leadership skills. Your dog should view you as being similar to a teacher, a mentor, or a team coach. There needs to be rules, which must be followed in order to gain rewards. If you don't already have your dogs on a feeding schedule, get them on one. This means they each eat a specific portion at scheduled mealtimes, and only have 20 minutes to eat at each mealtime. This puts you in control of the food, a major resource. They must do something to get their meal, for example, an obedience cue you might be working on like "sit" or "stay". This way, they earn their food, you gain leadership, and everyone's happy. Use similar strategies for other routine activities and privileges, like having them "sit" and "wait" while you put on their leash, working on leash-walking skills with them, etc. Keep the rules the same for both dogs. Get a qualified trainer to help you teach your dog obedience cues if you need help. The old phrase "old dogs can't learn new tricks" is absolutely untrue. I've had dogs as old as 15 in my obedience classes that did phenomenal in the class.
    What does that have to do with the growling? Teamwork. They need to accept you as the team leader, and each other as teammates. Then, you can work on your Shih-Tzu's socialization. Without evaluating the dog, I can't tell you exactly what's the underlying cause of her snapping at your Cocker Spaniel. I can tell you that regardless, ensuring she gets rewarded for the correct behavior and not rewarded for the bad will eventually alleviate the behavior problems (as long as they aren't medically based). Every time your Cocker Spaniel walks in the room, and your Shih-Tzu doesn't growl, reward your Shih-Tzu. You can use treats, praise, petting, a favorite toy, or a combination of those to reward with. This will help her associate the Cocker Spaniel with good things, and that good things come when she is displaying the correct behavior (quiet, calm, playful, social, etc.) Reward any time you catch your Shih-Tzu having a positive interaction with your Cocker Spaniel.
    Additionally, don't reward when your Shih-Tzu messes up. If she is fearful, growling, or snapping at your Cocker Spaniel, DO NOT give her attention or any rewards. This includes the common mistake of talking to the dog to encourage it while it is displaying the unwanted behavior. An example of this is the owner who says something to the effect of "Fluffy, it's okay, she's a nice doggie, don't bite her..." and/or picks the dog up or pets it. This rewards the bad behavior, so make sure you aren't making this mistake.
    If this doesn't help, seek the help of a trainer in your area to help evaluate exactly where things are going wrong. Often, it is something you may be completely overlooking. Don't expect too much too fast, there is never a "quick cure" that is effective long term, regardless of what TV shows would like you to believe. With time and consistency, the problems should subside. Let me know if you have any more questions, or details regarding your question. Good luck!