When you introduce a new feline resident to one who is already established in the home, there will be a certain amount of hissing and growling. Since the female is more or less still a kitten, the older cat will "correct" her if she gets into his space. This is nothing to worry about as animals do this in the wild as well. Make sure both cats have their own litter boxes and food bowls. I would not hesitate to get the female spayed as soon as you can. This is kitten season, and should she get outdoors, she could become pregnant. In addition, it will calm her down and she will accept living with another cat much easier and become less agressive. She should be kept separate from the male for at least a week. When you let her out, do not leave the cats unsupervised. I doubt seriously, unless the male cat is always very aggressive with everyone and other cats, that he will not "come around". But he is the resident cat and should be given lots of love and treats by his favorite people.

Izadore (Izzie) answered 2 days, 14 hours ago. Helpful? / 1