I have a 5 year old female cocker spaniel, and 2 four month old tabby cats one male and one female in the house. The two cats were fixed today and now that they are home they are fighting. Both are perfectly okay with attention from people and our dog, but if one of them even looks at the other from a close enough distance they begin hissing and meowing and if they get close (which we are trying to prevent) they fight. I'm just wondering if this is normal and what i can do about it. If it is normal how long will it last? They've been together since they were born and have never had this problem.