Welcome to Just Answer. My name is Jane. I have been involved professionally with dogs in the healthcare and behavioral fields for over 20 years. I’ve worked as a Vet Assistant and Behaviorist and have extensive experience in dog reproduction, as a breeder, for even longer than that.. Canine behavioral issues and training are also my specialties. It will be my pleasure to work with you today.
It is always a tense situation when you bring two females together. It sounds like your foxie is a dominant dog but the Shih Tzu was the top dog in your daughters house. So now you have a dog that is used to being the top dog in the household and having another dominant dog come into the home and trying to take her place. Your dog is going to do things to challenge the Shih Tzu such as pushing past her to get attention, possibly trying to take one of the Shih Tzu's toys or even sitting in the Shih Tzu's favorite spot. Of course, the Shih Tzu would not feel like she should give up her place so Foxie would feel like she needed to reprimand her so the Shih Tzu's sees Foxie as the boss.
Often when bringing a new female into an established household, it makes for a very difficult situation for the dogs unless one is very submissive. If the Shih Tzu is not doing much fighting back, she is submissive but your Foxie still feels the need to reprimand her so she definitely knows her place.
Now you can help stop this behavior by obedience training Foxie. If Foxie has had obedience training then you need to go back to formal training sessions again. The following site is helpful in helping owners train their dog. Be sure and click on the link to the page on obedience at the bottom. and links on subsequent pages leading to detailed instructions.
Training works best if you train at least 30 minutes a day (two 15 minute sessions). I would start making your dog work via the Nothing in life is free program (NILF). It is outlined below.
You should not show Foxie attention unless she earns it. She should also not be on the furniture as it encourages her to think she is in charge. Dogs that are allowed on furniture (even if put on the furniture) tend to feel that since they are elevated to your level or higher if on your lap, they mentally feel elevated as well in the pack order and thus are the boss. Keeping them on the floor can help lower them mentally back to a submissive position in the pack. So the first thing is to not allow him higher that the humans or even on the same level. Attach a leash and use it to remove him from the furniture. Give a correction in the form of a short tug to get his attention and firm "NO" when he attempts to get on and a treat when he starts not trying to get on the furniture. Thus you are providing consequences for the getting on the furniture and positive reinforcement for the desired behavior (not attempting to get on the furniture).
The same should go for the Shih Tzu as well. The next stop would be additional group training with the two dogs in question. Both dogs should be leashed and if one dog even looks at the other dog, a correction should be done. Any sign of aggression including a prolonged look, hair raised on the shoulders, a growl or even a stiff legged walk, should be corrected. A correction is a quick tug of the leash and a firm low toned "NO". Once you have done this couple of times, you should notice the dogs ignoring each other. When that happens, you will want to reward them for the desired behavior. Again, use tasty treats like the hot dog slices. This teaches the dogs that you WILL not tolerate fighting in YOUR pack.
Learn dog body language so you can tell what signals the dogs are transmitting to one another and head off any dominant or aggressive signals before they escalate into a fight. It will take some time to correct and work on your part and your daughter but both dogs will be more of a pleasure to own once trained.
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