Fighting dogs

Question
Jill,
We have 3 dogs.  We adopted 2 puppies at 8 weeks old from the humane
society 3 years ago.  One is dachshound/lab mix and the other is a
husky/heeler/border collie mix.  They are both every sweet dogs.  The lab
mix is the dominant one.  The husky mix is insecure but very sweet.  The
husky has shown signs of herding behavior to yard people and kids so we
introduce them slowly then there is no issue.  However a month ago we
rescued a bearded collie the is a male.  The other two dogs are females.  The
bearded collie is non aggressive just happy to here.  I do believe bringing him
into our house has made the other two unstable.  I also don't think removing
him will solve the problem as they don't pay him any attention.  All three
dogs walk together with no problem.  All three have been to obedience school
and are well behaved.  I hear so many different things when it comes solving
aggression issues between dogs.  All three dogs have been spayed and
neutered.  They are not aggressive  toward us or our children or the cat.  I
practice obedience with them almost daily, walk as often as possible and the
two females come in and sleep in front of the tv at night.   The two females
have started fighting.  They are pretty aggressive when they fight, yet when
you brake them up and bring them in they lay down next to each other and
go to sleep.  I don't understand it.  They just can't be turned lose in our yard
together without fighting.  Do you have any suggestions?

Answer
This is a very complex situation that requires in person evaluation.  I don't understand why any "humane society" would allow you to adopt two puppies of approximately the same age and the same sex.  You might mean "kill shelter" as in municipal shelter.  These two females appear to be developing a rank related problem.  Your two females are "ignoring" the new addition because that is what higher ranking members of a pack do to make a statement; this is normal.  However, the addition of the third dog appears to have precipitated a rank opportunistic struggle between the two females.

You require the expert evaluation of all three dogs (independently) and evaluation of their interaction together; you need to be taught how to observe dog body signals (communication) and you need to obtain a clear picture of which female is the most dominant between the two (your evaluation doesn't seem adequate.) You determine that the "lab mix" (perhaps an erroneous mix perception) is dominant because the husky mix (ditto on erroneous mix perception) is "insecure but sweet".  Regarding dog to dog pack structure, your observations are irrelevant.  How these dogs relate to one another (in ways you are not perceiving) determines rank structure, NOT how they relate to humans.

You need to contact the veterinary college in your geographical area and find a certified applied animal behaviorist who can do what's required, IN PERSON, to determine "who is who" in your pack, and you need to do this ASAP.  Because a dog can perform obedience "tricks" does not mean it will not interact with other dogs in the household in a manner that you find acceptable.  These dogs have no clear structure; that means, your training and interaction with them is not GIVING them clear structure.  You need expert guidance and you need to obtain some psychological control, using positive reinforcement training and behavior modification of all three dogs.