Fannie and Olga,

I appreciate your thoughtful responses. I was wary of using the muzzle and am very much against it in most cases - I have only used it on one foster dog which was extremely aggressive. Keeping the dog in question separated with strategically placed baby gates and unfolded exercise pens with her sister has worked out well so far. I'm keeping them out of sight from each other as she would get her hackles up and begin curling her lip if she even saw my dogs or cats in another room.

I did notify the owner of the behavior, and from her response, I gather that this is normal behavior for her. It seems that she has unaddressed aggression issues and may not have been socialized well. Some of it could be attributed to stress/anxiety, but both dogs appear very relaxed and are not displaying any visible signs of stress.

PREFACE: I have 2 dogs of my own and 2 dogs I am sitting. I did a meet and greet well in advance with the client and her dogs, and everything went great; the dogs were getting along great so I agreed to do the sit. My dogs have never shown outright aggression towards other dogs or had other dogs display aggression towards them.

One of the client's dogs and my own get along swimmingly, but the other client's dog is behaving aggressively towards both of my dogs and cats regardless of what I try. I have tried:

• walks on neutral ground
• exercising her before retrying introductions
• conditioning

At this point, I have spent the better part of 3 days trying to integrate her, and I have even tried to let them work it out on their own. Alas, nothing has worked. I am afraid that she will hurt my cats or my smaller dog, but I am most afraid of her inciting a fight with my large German Shepherd mix which is much larger than her; he is not aggressive, but he will defend himself.

The client is hundreds of miles away and has no local contact. My question is whether it is okay to muzzle the client's dog, and if so, should I notify her?