my dogs fight (follow up)

Question
QUESTION: I have a Pyrenees/St. Bernard mix and my mother has a small collie kind of dog.  My dog is 125 lbs. and the collie about 45 lbs.  They've known each other for 4 years and sleep next to each other and play in the park with each other well.  The big dog is pretty nonchalant about everything but indulges the smaller dog.  On three different occasions, while they're playing with each other in the yard with me standing right there, the smaller dog suddenly starts snapping her teeth and attacks my dog with a vengeance.  Of course the bigger dog overpowers her and it takes a lot on my part to break them up.  The last fight a week ago was the worst.  The smaller dog ended up with bleeding gums and it seemed if I wasn't able to break them up, it would have been devastating.  Could my presence have precipitated the attack?  Would they fight to the death if not stopped?  Should I worry that it could happen to dogs at the dog park?  They've both been to the dog park many, many times and completely ignore all of the other dogs.  I appreciate your time and any answers you could give me.

Nancy

ANSWER: Dogs choose who they like and dislike, just as we do. Also, dogs will sometimes choose to guard resources or even their personal space.  I cannot tell what is setting your dogs off, since I cannot see them, but the first thing to do whenever a dog exhibits sudden aggression is to have a vet examine the dog to rule out any physical causes.  If the dogs are both female, and have taken a dislike to one another, there is danger of a very serious fight and some dogs will fight to the death. In any case, with one dog outweighing the other significantly, and the fact that they seem to be escalating, I have a high degree of concern.  With males, usually fights are ritualistic, with females, things can get serious.  In any case, I would not subject my dogs to this kind of stress - is it really necessary for them to be in each others company?  If you want to evaluate the situation with a professional, you can find one at IAABC or the Animal Behavior Society web page.

---------- FOLLOW-UP ----------

QUESTION: I'm sorry I didn't include the fact that my father recently passed away and my mother now resides in an assisted living facility, so I have taken her dog into my home until...  They are both spayed and are friends otherwise with the collie often laying with her body touching my dogs' body.  Their fights so far, have occurred only about once a year and out of the blue.  Soon after the fight, they're back to being OK.  The bouts all happened while at my parents house in the field across the street.  Maybe now since the collie is at my house it will end?  Thanks again for your time and I'm sorry I wasn't more descriptive as I should have been.  If it's still possible they could fight to the end, then the collie will be given away.

Nancy

Answer
Even if they don't "fight to the end" one of those dogs might be fearful and anxious - is it really worth it?  You may want to contact Collie rescue *before* something happens and the dog is unadoptable.  It's possible that they may work things out, but if they were my dogs, I might be inclined to consult a behaviorist to evaluate the situation in person.