If your Siberian is food and toy aggressive, chances are she'll be aggressive over the attention you would give another dog. The safest thing to do would be to wait until something happens to her and then, if you want two siberians, consult with a reputable breeder and find out the temperments of the puppies and the parents. Perhaps you would be able to get littermates.
If you are willing to take on the risks and responsibilites of having an alpha Siberian and bringing in a new dog, here are some suggestions.
Try introducing a male instead of another female. Two females will fight faster than a male and female. You'll want to make sure he is fixed, of course.
Puppies produced from a female with food aggression are likely to have the same problem.
Try introducing an older dog. You female will be less likely to hurt an adult. Introducing a puppy to her could mean risking its life.
Before bringing another Siberian Husky into your home you should try breaking the female Sibe of protecting her toys and food. One way to do this is hand feed your dog. Let her know that you putting your hand near her dish brings good things instead of her thinking you may take it away from her.My husky wouldn't eat her food when I first gave it to her she would guard it for hours and not let anyone touch it.
It will take some time to break her of this..but you can either take little handfuls at a time and put them in her dish and when she eats that, give her another scoop. Or you can just hand feed her. She will learn you are the one giving the food, and will learn your hand is good.
For toys- a good way to break your dog from being toy aggressive is don't let her win the toy. Letting your Sibe win the toy is showing that she is more dominant than you are. Let her play with her toys and when you want the playing to stop put it up where she can't reach it.
This will show that you tell her when she can play and when she cannot.
I think it is great to have more than one Siberian Husky. They give each other something to do. I have read that if you put two Siberian Huskies out ( in a fenced in yard) they will be less likely to try and escape because they have a friend ( another sibe) there with them.
Before you consider anything you are going to want to address the agression issues. For some dogs food agression can be easily curbed.
Number one, you eat first. With a Siberian husky there must be a pecking order and you need to be on the top of that. Second start to hand feed them but only after you pretend, (Or actually if it's a yummy treat) eat the food first.
They need to understand that the food is yours not theirs and that you are only "allowing" them to have some.
If this doesn't work then the issues can be more deeply rooted and I would HIGHLY suggest consulting a dog behaviorist. (I am not talking a pet smart dog trainer) but someone who knows how to modify a dogs behavior.
These are all great answers and the only thing I would add having bred Quality Siberian Huskies for over 25 years is this.
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