Aggresiveness

Question
My Three one year old shih tzus have always gotten along until just after there last heat cycle. Now everytime I let them out together all they do is fight and attack each other. Do you have any suggestions or reasons as to why this may be happening?

Answer
Did you breed any one of them?
Anyway, they are going through the change, just like teenage girls do.  No longer little girls now they are squabbling teenagers and fighting over who is the boss, who goes out the door first, who potties where, who sits on the right side of the lady of the house and who sits on the left.  Before it was all about play and puppy stuff and know that hormones have kicked in their instinct to reproduce, establish dominance, etc has kicked in.  In a few weeks when they have gotten their issues aligned amongst themselves it will have all calmed down again.  It will happen again when the heat cycles come and you breed one and not the other and one is jealous that she is not got puppies, you will have false pregnancies.  Trust me the fun is only just begun.  The best thing to do is allow them some space to work it out but if it starts to get to aggressive immediately stop it by clanging a pot, squirting them with water, or whatever works to get their attention and say NO! then put them in separate areas (time out)for about 10 min or so till things calm down and then let them gradually back together if they start back up separate again until they can come back together without fighting (believe me it will happen) and it should only take a few times of this, if it takes more than I would not want to ever breed the aggressive female EVER.  If your not planning on breeding these girls by the way..sorry I was talking as if you were since they were a year old and you had not had them spayed.  Please get them spayed, an unspayed female is at risk for many health problems.  Hope this helps and good luck