I totally agree with Melanie about how to go about getting into the leadership role. I do not agree with the pack theory that your trainer suggested....about reinforcing the "dominant" dog. Reward pushy and you'll get pushy. I would remove the dog at once that is instigating the pushiness or snarkiness. Hard to determine sometimes, as you don't always see a signal coming from the "innocent" looking dog. You need to learn body language and expressions well and catch it at the very first sign of intention, interrupt, isolate for a very short time, try again....that is if you're going to try to re-train them to "behave" together....very difficult in a case like this, I think.
These dogs have had hormones surging through their bodies and brains for a long time now. Behaviors have developed through the influence of these hormones. Brain pathways and firing neurons have developed for these behaviors. Behaviors require these things in order to be present. So, for a very long time, possibly the dogs' lifetime, these central nervous system pathways are going to be open for use, so to speak. Eventually, (but I don't think anytime soon) if they are not used, they will break off. (use it or lose it) As long as they can engage in the behavior after neutering, the neurons will keep firing and the integrity of the pathways will remain.
When dogs are neutered before the hormones begin to influence behavior that is based on those hormones, often some of this behavior can be thrawted. But once it's been going on for a long time, it is very difficult to erradicate.
So, my point is that although training will be VERY instrumental in this problem and neutering too, will probably help a little bit, I doubt very seriously that you'll ever be able to safely take your eyes off these two dogs. They will probably be stressed living together. And as difficult as it sounds, unless they're kept seperated or heavily supervised, there's a high liklihood of them fighting to the kill. It happens. Yes, some dogs get along well and can live together. My dog's breeder had two intact males that were not the same breed. But she still didn't leave them unsupervised, just in case.
But these two have already shown you that there's a big problem. So, you'll either have to be unbelievably diligent and careful or re-home one of them. It sucks, but it's the way it is sometimes. I hope things improve for you.
