Behavior Issues!

Question
Hi, Please note:
**I have a Male German Shepherd, 2 years old. NOT FIXED!
**I have a Male Pug. 4 years old. NOT FIXED
**I have a FEMALE PUG. Less then 1 year old. IS FIXED!
>>Here is the situation.
Before we brought home the NEW Female Pug, the Male Pug and the Male GS got along GREAT! I really mean....GREAT! They played with each other all of the time. Best Buddies to say the least!
**Now.....Since we brought home the new Female Pug and even after we had the female spayed, we have notice a GREAT increase of aggression from the GS.
**The Shepherd is VERY aggressive toward out Male pug. Several time during the day, we have to keep yelling at him and scalding him for showing his teeth, etc. towards the Male pug. We are worried that he is going to hurt/attack the Male pug.
**The GS is very friendly towards the Female pug!
**When (anyone) now comes to the door. The GS acts like he wants to bite them. Even if he knows who it is. It doesn't matter!
**WE are very concerned about this CHANGE in behavior!
**To the best of our knowledge, we know he isn't sick in any way. We know he doesn't have anything like lyme disease.
>>What do you think is going on here besides the fact that the Male GS is just trying to be the Alpha Dog here?
>>Do you think is we NOW got him fixed, if this would make any difference? Or is it too late for that?

Please help!
Any suggestions would truly be appreciated!
Thanks!!  

Answer
Hi Tom B,
Thanks for the questions. Neutering male dogs does not "cure" aggression but does reduce roaming behaviors and marking behaviors. In addition, it is said to make dogs less "reactive".

So yes, neutering would be a component of any behavior modification plans that include surgical solutions. That being said, will it help? . . it depends on how long the behavior has been occurring.

Once dogs get addicted to the brain chemicals associated with aggression, neutering the dogs usually does not achieve the clients' target goals of no-more-aggression.

Which male would you neuter?

Since you've ruled out medical possibilities, I'll take a wild guess and say his his change in behavior is totally due to the fact that he is reaching social maturity AND he is unsure about his environment.  

The addition of the female was probably a trigger, but not the cause. The aggression towards strangers is another  symptom of the same problem.

Fortunately,dog-dog aggression is a well-studied subject and there are some good books. The best place to begin is "Feeling Outnumbered? How to Mange and Enjoy a Multi-dog Household" by Patricia McConnell.

If you can, locate a certified trainer near you. Everyone can benefit from a help of a coach! Visit http://apdt.com