Angry cat...

Question
I have two cats, sisters from the same litter. I got one a year before the other. They have been in my home together now for over 6 months. The one that came later kind of pesters the other... to the point of messing with her while in the litter box. It was aright until they got neutered and now it is worse than ever. The one that pesters is so mean to the other she won't even come out of the room. I had to bring the food and water to her and lock the other out. Then later on lock the mean one up and let her roam the house and use the litter box. The mean one will even go find her where she is hiding and attack her for no reason. She is so scared of her sister she hisses and her hair rises if she even thinks she is coming... I've tried the water bottle and loud noises to let the mean one know she is doing wrong. They just got back 5 days ago from getting neutered... What do I do?

Answer
Liane,

That is normal behavior for alot of cats after one gets spayed or neutered. Cats go by smell and not by sight in recognizing other cats (with humans, they go by voice...not by sight). Your spayed cat brought home MANY different smells from the vet: anesthetic, medicinal smells, and smells of other cats...all clinging to her fur and skin. The sister cat thinks she's another cat because she doesn't smell the same! She is protecting her territory from this 'intruder'. Things will settle down  when the smells are gone from the spayed female.

A trick that I've heard a lot of people use in that situation (though I have never tried it) is to put a drop of vanilla on each cats forehead so they smell the same.

You can try a popular cat calming spray and plug-in called Feliway, or Comfort Zone with Feliway. It is available at pet stores like PetSmart, Petco, etc., a vet's office (they use it too), or on-line. It copies relaxing pheromones that cats produce from rubbing their faces on things.

There is also another cat calming product that you can add to her food or water that reduces anxiety called Bach's Rescue Remedy. It is available on-line and in health food stores. Here is a link about it: (copy and paste, or type the whole links into your address bar)
http://www.bachflower.com/Pets.htm

As a last resort, if the aggressive cat doesn't calm down, you can speak to a vet about getting a prescription for 'kitty Prozac'. It is a popular medication for calming stressed and aggressive cats. Usually a short term dosage (about 2 weeks) is enough, though rarely a cat needs it long term.

If the sister refuses to accept the spayed female as the same cat then you may have to start the slow introduction process all over just like she was a new cat you just got. Research my previous answers for instructions. Hopefully she will settle down and you won't have to do that.

I hope this helped.
Tabbi