Set up a meeting in a neutral area so that your Chihuahua does not feel territorial and is not encroaching upon another dog's territory. The space between your yard and a neighbor's or a small area of a quiet park will work best.
Prepare ahead of time, you want your Chihuahua to feel as comfortable as possible. Make sure your dog is not hungry and does not have any bathroom needs. Do not rev your Chi up by playing a lot or over exercising him or her. Put a harness
on him or her (NOT a collar, for this breed, a collar will put too much pressure on the neck and could lead to collapsed trachea- a health issue common with toy breeds), them put a leash on your dog and hold on to it tightly.
When the other dog is introduced, keep all voices calm and peaceful. Your Chihuahua will pick up on the tone of your voice. Allow the dogs to smell each other and have time to figure out just who the other one is.
If your dog immediately barks, nips at or goes for the other dog in an aggressive way, immediately pull back on the leash. (Be sure you are using the harness, so force is safely displaced over the chest, shoulders and back). Give a strong and firm command of "No!". Keep your Chi at your side with the leash short and taut so that he or she may not leap or run.
If your Chihuahua continues to bark
or jump up, give the command word of "Sit" or "Down". If he still continues, bring him into another room of the house or if outside, back up several steps.
During this time of distance, both owners should 100% complete ignore the aggressive dog. If the aggression seems to be riling up the other dog, it may be best to call of the session and try again another time.
In many cases, after being completely ignored - while owners are chatting to each other in a friendly manner - the Chihuahua will calm down. If so, in a happy and pleasant tone tell your Chihuahua that you are going to try again. Walk your Chi over to the dog and try again.
Whenever your dog is calm and behaving well with the other dog, give both of them a treat. Do not just give one dog a treat, as this may trigger a negative response in the dog that is being ignored.
If the dogs are getting along well, try to not get involved. They need time to interact and "speak dog" to each other. If owners keep stepping in to pat the dogs and act excited that they are getting along, this will excite the dogs and confuse them. What are they supposed to do? Play with each other or pay attention to their owners?
It is important that negative behavior be dealt with immediately. This should always be the same actions. Your Chihuahua must be pulled back from the dog. He must hear your strong and commanding "No!" and he must be ignored for several minutes.
It is just as important that good behavior be rewarded. Your actions should always be the same. Small treats can be given to the dogs at random intervals when they are getting along, your voice should be showing approval and happiness and when the dogs are done with their meeting you should shower your Chihuahua with praise for getting along with another dog.
As you do some introductions to other dogs in this control way, you may notice that your Chi takes to some, but not to others. While it would be ideal for our pets to get along with all other animals, this is expecting too much for a dog prone to aggression. There are many reasons for a pair of canines to not want to interact, including a difference in age and gender. Be pleased if your Chihuahua learns control with some and do not push or force interaction with others.
If your dog does appear to become tolerant of certain dogs, you can progress to arranging play dates. Do keep an eye on both your Chihuahua and the other, for any signs of aggression
. If they learn to get along, you can move these sessions into your home, to show that accepting the presence of another in the house is expected behavior as well.