Expert: Tina - 12/19/2008

Question
Hi,
I have 2 cats - male and female about 6 years old, both neutered/spayed.
They have been together since birth and sometimes play fight etc.
Today a stranger cat showed up on my deck, it could not get in and my cats
not out, it just looked at them through the window. Suddenly my male cat
became EXTREMELY aggressive towards my female cat and I had to separate
them, he also hissed and growled at me but did not hurt me. Eventually I had
to leave for work. When I returned they came to greet me but then the female
cat started growling at the male and more fighting ensued. She is currently on
top of the kitchen cabinets and growls up a storm when he goes into the
kitchen. He is acting more normal but the few times she has come down from
the cabinets he has chased her and she responds with growls and hissing and
returns back to the top of the cabinets.

They have never been like this towards each other and clearly it has gone on
all day. I'm sure it must have something to do with territory/feeling
threatened by the cat on the deck but I don't know why they are attacking
each other or how to solve it. I'm scared they will really injure each other. I've
never even heard the female cat growl before and now she won't stop.

Do you have any suggestions how I can help to resolve this? Should I be
behaving towards either of them in a specific way? Should I try to separate
them behind closed doors for a while?

It's upsetting because they normally get along well and now are like
strangers/enemies.

Any suggestions gratefully received!

Answer
Hi Sharon,

This is called re-directed aggression and it's fairly common but of course it is very disheartening to see your cats not get along!

i recommend immediately separating them for the time being, and re-introduce your cats over a period of 1 week as if they were strangers. Follow the suggestions here:
http://catnet.stanford.edu/articles/introducing_cats.html

Also Feliway spray around windows and doorways can help ease territorial aggression.

Finally, try to make sure neighborhood cats can't get into your yard - either with cat proof fencing or try a cat repellent outside:

scroll down to the bottom for cat-proof fencing:
http://catnet.stanford.edu/articles/enclosures.html

cat repellents:
http://www.critter-repellent.com/

http://www.ssscat.com

Good luck!