Aggressive cat behavior... ?

Question

I have two cats. My roommate, who's been living with us for almost two months, had a cat as well, so between the two of us there are three cats in the apartment. Things were a little rough at first, as they always are, but they settled down fairly quickly. Except now, my roommates female cat, who is under 6 months and isn't spayed, is acting very aggressive towards my female cat. She hisses, fluffs up her fur, cries, and takes swings if my cat gets too close. My cat pretty much ignores the kitten, so I know this isn't a response to antagonizing. Any thoughts on why this is happening?

Answer 1

get her spayed, and some cats just dont like each other. i have two spayed 15 year olds that have lived together for 14 years, have been spayed for 14 and a half years, and they fight every day. as long as they do not run into each other, they are ok. if one jumps on the bed while the other is up there, they box.

Answer 2

Could be that the 6 month old is in heat.

Answer 3

You should most likely get her spayed because cats who are in heat are most likely to get aggressive towards other cats.  

Answer 4

Sounds like your flatmate's cat is becoming more territorial as she gets older - as they all do. It might calm down if she's spayed, or it might not; female cats tend to be quite territorial even when they're spayed.

The best you can do for now is make sure none of the cats are suffering from this aggression. Maybe get a water pistol to break up any fights... that might train your flatmate's cat that randomly attacking other cats she's living with is not a good move.

Answer 5

an unaltered cat is very territorial, and very possessive of said territory.  If there is any way to get that cat spayed, it will help a lot.

Increasing the territory will also help.  I know you can't add rooms on to your apartment, but you can think three dimensional.  Add cat trees, or perches for the cats to get up off the floor on.  Allow cats on furniture will allow them to sit at different heights, increasing the area for them.

there is a book called Cat vs Cat that is very helpful in figuring out disputes between household cats.  Just because your kitty *seems* to be ignoring the other, doesn't mean they aren't doing subtle things to antagonize one another.