My 12 year female jack russell, is beginning to get vicious with me and trying to bite when she does not get her way. She is very aggressive when I eat something and keeps trying to get the food anyway that she can. She thinks every time I eat I should share it with her. I have tried putting her in her kennell and she keep barking and trying to get out.

She certainly doesn't recognize you as the alpha in the household then. How long has this been going on?

Tick

I agree with tickle. Your dog is displaying dominant aggression towards you.

But that usually doesn't happen from one day to the next. If your dog has not previously acted this way towards you, then you need to determine what has changed to trigger this behaviour.

So, I second tickle's question. How long has this been going on? And has anything changed before and after that point in time? Sometimes when dogs become ill or are injured, people change their behavior towards them because they feel sorry for them during the dog's time of need. This is seen as weakness by dogs with dominant tendencies (and Jack Russells definitely fit that description). And instead of being grateful for the owner's sympathy, they become aggressive.

Afterwards, because of the sudden change in the dog's behavior, people that don't understand dog psychology become fearful, feeding the vicious cycle of dominant aggression and the dog becomes worse. They see the owner become weaker and they become more dominant.

To stop this cycle and begin to rehabilitate the previous relationship, the owner needs to regain dominance in the relationship. This doesn't mean that the owner becomes as aggressive as the dog. The owner simply reacquires the respect that was lost by behaving more assertively towards the dog and exhibiting behaviors which the dog understands.

In order to learn how to do this, I recommend you get some books by Cesar Millan or get his DVD's. There are other dog psychologists out there, but I believe his methods are the best because they are the easiest to implement.

I hope this helps.