Hi, I have an 18mo neut 55lb mix who is very sweet and submissive with other dogs. I offered to foster a 6yo small mix spay female because I thought she might be perfect for us to adopt. Things were going pretty well other than my young dog wanting to play too much with her but now she seems to thoroughly enjoy playing and rough housing. The foster is not food aggressive or toy aggressive. BUT in the almost 2 months since I have had her she started a real fight a few weeks ago. I was petting her and my dog came over for petting and she went for him but no bloodshed. Then things seemed ok until other day when they were both laying on bed with me and I think she was asleep but my dog accidentally touched her while he and I were gently playing with a floppy toy, she snapped at him and caught my hand but didn't break the skin. Then yesterday they both tried to jump on bed and perhaps he bumped her because she started a fight in mid air and I yelled at her and broke it up, again no bloodshed. We had wanted to adopt her but I don't want my dog to become reactive toward dogs if she gets worse. Haven't been in this situation before and not sure whether I should expect it to worsen or whether it can be managed. Oh needless to say she is not allowed up on bed anymore and I am making her sit for treats/food/petting etc. She is adorable otherwise and my dog seems to enjoy playing with her. I know she needs a good home so I feel bad not adopting her but on other hand we like a peaceful home so not sure. Thanks for any advice annhishmen

I am not an animal behaviorist. You might want to consult one of them thar folks. This is advice from a fellow dog lover and handler, not a professional.

Whew. Now that the disclaimer is out of the way...

As you know, there are a lot of reasons for aggression. From the scenario's you describe (she was being loved on, and attacked a dog who approached. She was trying to climb onto furniture, and attacked a dog who tried to do the same) it seems like you're dealing with a dominant, aggressive dog. I say "seems like" because there's no way to really diagnose her without seeing her and testing her. Apart from contacting an animal behaviorist, I would read this article:

http://www.leerburg.com/groundwork.htm

Specifically, tethering her to you. Making all furniture off-limits, period. Watching her very closely around your other dog.

There are a lot of things you can do to improve this situation. Or at least, things you can try.

She may respond well. It's possible that she won't respond and will continue to have dog aggression issues. I sincerely hope that this isn't the case, you've done a wonderful thing in fostering her.

I want to thank you taking her in, but I think you need to change how you live with her. You should crate her more and keep her on 6ft leash. What you need to do is do the groundwork with her first.

http://www.leerburg.com/groundwork.htm

You don't want to let her have all the freedom she has right now because she is making rules. She gets into fight with your other dog because she sees him as lower rank. Since you haven't provide a good leadership, she's taking it over. She knows she has the power to control everything now not you.

Right now, you only let her out when it is time for potty. You keep her on the leash and then take her back to the crate. You do not play or give any attention to her. Act like you ignore her because a pack leader always ignore everyone. Everyone wants to be with the pack leader, trying to catch its attention. A popular girl doesn't have time to say hi to everyone so she expects everyone to say hi to her first. When you want to reward your dog's attention, it always come for a good reason. You take her for a walk and keep her by your side or behind you (never front of you).

After she realize that all of the attention she used to get is GONE, she will beg you for more or even pay attention to you more. You only praise her when she does something right.

Very very good advise Lindsey, I second that opinion...she is new, and should be kenneled and on a lead