Cats Territory

I have two cats who both go outside during the day. There has been a new cat around who comes into our cats "territory" and even tries to come inside the house.

My girl cat sits and hises and moans at this new cat and my male cat sems more afraid and hides behind my female.
As far as I can tell there has ben so actual fighting. Should I leave them to fight out there territory oe remove them like I do. I'm afraid that I'm showing the new cat that she can be in my cats territory by taking them back in the house.
I just dont want them to get hurt.

Thanks in advance for the help

[Savas]

By letting your cats go outside you allow them a certain responsibility and freedom of action/choice that are normally denied to indoor cats.

So...by separating them, you're only prolonging the inevitable. It sounds like the new cat might be looking for a new home. Does it look like a recently dumped stray or is it a long term feral? (you can usually tell, their are signs).

What you really need to decide is if you're going to take steps with the stray cat. Are you feeding it at all? If so, it will feel welcome and come back. Perhaps you can trap it and take it to a no kill shelter or rescue group?

Generally, cats work these things out for themselves, with a minimum of blood, if you remove the following from the equation; sex and food. If all the kitties are well fed, and your two kitties are fixed, then they have little reason to get into a vicious, knock down brawl.
But there's no gaurentee how it will go.

[Misty1980]

Thank you for your advice Savas,
    I live in a house shared by others so it is difficult to tell who's cat belongs to who.  I have assumed this cat is owned by someone in the house. This new cat does meow at my female(who is fixed? I font know the proper termonology) as if the cat wants to be friends, but my female dislikes every cat that she comes across. She even only tolerates our male cat because she has no choice.  She can be a very Jelous mean little girl when she doesnt get all the attention.  

     I will ask around to be sure who's cat it is before I take any other steps in feeding or thinking about a shelter.

Thank you again for your advice

[Savas]

Good luck. Hopefully someone will lay claim to it and take responsibility.  There are sonic devices that drive off animals/bugs. I've never used one, but I hear they work fairly well.