Aggressive adopted poodle

Question
I adopted an 8 lb, 3 year old toy poodle about 7 months ago from an animal control/shelter. He is a super sweet dog- very playful with people or just by himself. He likes to sit on my lap but is just as happy to curl up on a chair. He is very intelligent- in the first month or so, I tought him to sit, down, leave it, get in his cage and roll over. He also learned to jingle bells on the doorknob to let me know when he needs to go outside. I feed him Science Diet food, give him Greenies and Blue Buffalo treats and fresh water all the time. He is crate trained for when I am at work 40 hrs each week, but remains uncaged with full access to the apartment whenever I am home. He's current on his vaccinations and got a clean bill of health from the vet. He was neutered in the spring, his teeth are good, he is on flea and heartworm prevention, and I like to think he is very well cared for. Unfortunately, I have no idea of his past history with his original owner. He was adopted by a family with small children before me, but was returned to the shelter because of his behavior with the children.

I myself don't have children, and aside from the dog i live alone. I know he has not been mistreated in my home, but he has been exhibiting some very aggressive behavior. He has shown a little aggression if he thinks you are going to take a treat or toy away from him. If he brings the item to you, its ok to take it. it's only when he is using it independently. He has never shown any aggression with his normal food or water dish, even if i pick them up while he is standing over them eating.

The biggest problem is that he seems to scavenge. He has pulled food packaging out of the trash can the minute I turn my back, and he holes himself up under the couch, or on the couch or bed, and if you even acknowledge the situation verbally he gets absolutely ferocious. snarling, bearing teeth, growling, lunging and wolfing down whatever he has, edible by our standards or not. I've never been afraid of a dog- even dogs that I've been told are mean. I've never had a dog behave this way toward me, and I am terrified that he is going to hurt a guest or myself. During these episodes, I do my best to be in control and assert my dominance, but I do not want to be bitten, and I dont doubt that he would bite me.

I feel like his previous owner must have beaten him badly (he doesn't cower the way a hand-shy dog will, but bristles and snarls), or else he was starved. It's speculation of course. I wonder if you could provide me with any insight as to why he may behave so fiercely, or what I could do to modify his behavior. I have thought about formal obedience training, but I don't want to spend the time and money if there isn't much hope of him becoming a respectable member of society. I'm honestly afraid to take him around other people and animals.

Please- can you help me?

Answer
Hello Erin,
I will give you some suggestions, but understand that since you said that he will bite you, you may get bitten doing these suggestions.  When you take on these suggestions, you will need to follow-through and be serious about it.  Your dog needs to know that you are BOSS and that his biting, growling, snapping or any other behavior ISN'T going to work.  
You might think about using a muzzle and heavy gloves to protect your hands, when working with him at first so you can estabolish your dominance without getting hurt.

The best thing to estabolish dominance is to hold your dog down on its side and make it submit before letting it up, but this can be dangerous because this is the most likely time for him to bite.  If he can bite you here in this position, then he can scare you.  If you let him realize that by biting you it won't scare you away, then you have succeded in letting him know that you are boss.  
*FOR THIS TO BE SUCCESSFUL, YOU CANNOT LET HIM WIN.  IF HE BITES, YOU CANNOT PULL AWAY, BUT MUST CONTINUE TO HOLD HIM DOWN.  HE WILL EVENTUALLY QUIT BITING BECAUSE HE SEES THAT IT DOESN'T WORK, AND THIS IS THE FIRST SIGN THAT HE IS SUBMITTING.  

For his being possessive with his toys, you are going to have to teach him that they are YOUR toys and he can only play with them because you give them to him.  
Take his toy and drop it at your feet.  Put his leash on him if you feel he will need it.  Don't let him get it, but make him submit to you.  Walk toward him and make him back away.  Pick up the toy and rub your scent on it, then put it back down and again, make him back away.  Pick it up once more and then give it to him.  

You need to use this with his food bowl also.  Make him sit for it before you will put it down.  Next, make him come up to it to eat out of the bowl with you standing there.  Don't look at him or anything, but continue to stand there as he takes a couple bites, then you can step away.  

You need to teach your dog the "Out", or "Give" command.  To do this, get your dog next to you and show him the toy.  Let him have it and then tell him "Out" and have him give it to you.  Praise him when he does.  
*You might want to also teach the "Take It" command, and teach him to take it when you show him the toy.  
Now when you go to dominate the toy, you can make him drop the toy and submit it to you.  

For teaching him to leave the trash cans alone, you will need to teach him the "Off" command.  To do this, you need to put his leash on him and try to coax him on the couch or put him there.  Next, give him the "Off" command and make him get off.  If you need to pull him off the couch, do so.  Have him sit, and praise him.  
Anytime that he comes up on the couch without your permission (you asking him to come up) then you tell him "Off" and make him get down.  This shows him that its your couch and that he can only get on it if the Boss says so.
You can also use "Off" for him jumping up on people or getting in the trash cans.  Keeping trash cans higher up or by having one with a lid will help with this.  

You might want to teach the "Leave It" command as this will tell him that if you say "Leave It" that he is to stop what he is doing and back off.  
To teach this, get some bits of yummy food such as hotdog or chicken and cut them into bite sized pieces.  Lay them on small squares of paper and place them around on the floor so you can walk by them.  
Put your dog on leash and walk him around the treats.  Tell him "Leave It" when he goes to sniff or eat the treats.  Make him walk on by.  When he will walk by it without bothering it, have him sit by it.  When you are ready, you can pick one up and give it to him.  He has to learn that everything comes from the Boss.

This is very involved training and if you at all feel that you can't do it, please contact a Dog Behaviorist in your area.  Do realize that you might get bitten and that you have to be in control of the situation so that your dog doesn't win.  It would be better if you were able to do this on your own because he will learn to submit to you, by you.    

Give some of this a try and if you need more help or other suggestions please feel free to ask.
I hope this helps you some.  
Thanks for using AllExperts.com,
Kim