I tried introducing a new adopt-a-kitty, 10 month old male to a female I've had for about 2.5 years. Both are spayed/neutered whatever the correct term is. Upon bringing new kitty home, I kept it in a locked area of the house for about five days. The only option for contact with the other cat was under the doorway, although I never personally noticed any such contact. Inside the locked area were some favorite items belonging to the old cat. Introducing them, at first, they seemed very cautious of each other, but now the male (new cat) seems to just viciously attack the female (old cat). Anything I should try? I really like the new cat, he's way way more sociable than the old one ever was.