Adopting a GSD from Shelter

Question
I have adopted a 7 year old female, spayed, from the animal shelter. I have a 7 year old Australian Shepherd, neutered, They got along great for the first 2 days and on the 3rd day I had to break up 3 fights. There wasn't a "thing" that triggered the fights so I am assuming that it is an "alpha dog struggle". I have separated them for now with see through baby gates and they both cry and whine like they want to play with each other. I am now scared to put them together. Should I try a muzzle? Neither dog is aggressive towards humans. I do not know the back ground of the shepherd. Thanks for any help you can offer.

Answer
Are you sure it is a real fight?  Are their hackles up and quick, short snaps drawing blood?  If not, it may be play.  It might help to have an experienced person watch them.  

The key to most behavior problems is approaching things using the dog's natural instincts. Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog. Life is much easier if the 2 legged pack members outrank the 4 legged ones. You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at http://www.dogsbestfriend.com/ For more on being top dog, see http://www.dogbreedinfo.com./topdogrules.htm

With 7 year olds, that may not be enough.  You may need to have a behaviorists help.