I am trying to integrate my cat with a feral cat so I can bring him in for the winter. I will admit this is not going well. While they don't hiss at one another any longer, and I can leave the door open between them, it appears that as long as he doesn't cross the threshold to enter the house, she is fine; and as long as she doesn't cross the threshold of the door to go outside, he is fine. But after I pet him, she is PISSED, while he doesn't care one way or another if I pet her.
Any tips on integrating two adult cats?