Introducing adult cats: Old cat is chasing new cat! What should I do?!?

[JenniferM]

My old cat, Macy is a 2 year old female shorthair. She is smaller than the new cat, Winston, who is a four year old Himalayan. We have had Winston for almost three weeks now, and he has been roaming free in the house for almost two weeks. Last week we stopped shutting him away in his safe room at night and when I leave the house. He has been using both his safe litter box and the litter box that Macy regularly uses, and she has been using both as well.

Yesterday, Macy chased Winston until she got a hold of him and started to wrestle/bite him. Winston is being submissive, and he wailed when she got him. I separated them immediately. She is chasing him again today and swatting at his rear. She isn't hissing or growling at all, though. I shut her in the bedroom for a time out.

What should I do? Is Macy trying to play-fight? Why is she being so aggressive all of a sudden? How do we get over this so that they can get along better?

 

[woollysheep]

Keep them apart a bit longer. With some cats, depending on their personalities, it takes longer to introduce a new cat into the home and has to be done very gradually.

Sounds like Macy thinks she is being replaced. No wonder she is being aggressive. Shut up the new cat, not Macy.