First of all, hello and welcome to BPO! You've come to the right place! There are many kind and knowledgeble people here to help you
Aggression is not really common in saints, and I belive it has more to do with his personal history than his breed. Since he has been through so many homes, it is entirely possible that he was abused or neglected in the past, and odds are that he was not trained or socialized. Lucky for him he has finally landed in a loving home
There are three things you need to do to help eliminate his aggression: become an alpha, train him, and socialize him.
It is really important that you teach Butt that you are the alpha dog - the leader of your pack (family). That way he knows to respect you if you tell him to back down, and he also knows that he doesn't need to protect you because you are the protector not him. There are many things you can do to establish your dominance. Some of the biggest ones are:
- Make him do a sit/stay before he eats, so he knows you are in control of the food. If he doesn't stay, take up the food and try again in a few minutes. He can't eat until he listens to you... And if he is growling at your mom and she is over often, make sure to have her feed him sometimes, so that he knows she is also in charge of the food.
- You are supposed to eat meals before he does
- Don't feed him table scraps - if you want to give them to him, don't feed them from your plate, put them in his bowl
- You are supposed to walk through doors before him
- If you establish eye contact with the dog, the dog must avert his gaze first. If you blink or avert first, it makes him think he is dominant.
- He is not supposed to sleep in your bed or on furniture
- You should pet him only when you decide to pet him, not if he is asking for it (if he asks for it and you give it to him it makes him think he is in charge of deciding when he gets attention, and is thus dominant).
- Don't play tug of war unless you know you will win. If he wins, it makes him think he is dominant
 There are other things you can do to establish dominance, but those are the main ones. I know it sounds intense, but you have to remember that dogs are pack animals and they want to know their place in the pack - if they think they are higher than humans, that is what causes aggression. Also, once you have established your dominance you can lax up on these 'alpha rules'. I established my alpha role with my saint when she was a puppy, and she still respects it so I don't need to follow all those rules (and trust me, I break about all of them
).
One of the other things you can do for Butt is teach him basic obedience. You can either enroll in an obedience class, hire a trainer, or teach him yourself (you can find out how to teach pretty much every command either here or somewhere else on the internet). If you decide to try on your own, let us know and we can help you find out how to teach these commands. Some of the most important commands are:
- sit
- wait/stay
- down
- leave it/take it
- heel
- come
These commands to keep your dog safe. They can keep him from getting into trouble, ingesting bad things, and getting hurt or lost. Teaching obedience also reinforce your alpha status. There is a great training philosophy called "Nothing in life is free" (nilif) that basically says in order to get any reward (food, petting, walks, etc) your dog must first obey a simple command (ie "sit" or "down"). It really helps cut down on aggression by enforcing pack heirarchy.
Also, make sure you a firm voice when giving a command or a correction - if you are timid, and gentle with your corrections (ie, reassuring him everything is ok when he has just growled) it makes him think he was right to be scared or protective.
Another thing that will help cut down Butt's aggression is socialization. Part of the reason that he is acting out might be fear from being improperly socialized as a puppy.
