sudden aggression and personality change

Hi, I have two boy cats that suddenly changed personalities overnight. They are littermates that I have had since they were kittens. They're a little over two years old now, and in all the time I've had them have never shown any sign of aggression toward each other. At worst, they would play and get too rough, but I could always tell it was nothing more than play and they would be grooming each other a frew minutes later. They've always been inseperable, sleeping together and playing together.

As of today, they are extremely aggressive toward each other. My boyfriend was bitten trying to separate them, which has never happened before, and there is fur all over my apartment. It got so bad that I had to put them in different rooms. One of the cats is acting stranger than the other, he seems to be the one initiating the aggression and now that they are separate he is yowling and breathing the air in through his mouth.

I think one of the causes might be the neighbor's cat. She went into heat a couple of days ago. The thing is, my cats are neutered and have been since they were 5 months old. Could it still cause aggression this extreme? What are the signs of hormonal aggression in cats? Could it be something else?

Your neighbor's cat probably. Being neutered won't necessarily overcome the feeling that they should be doing something, and being the macho males they are, they're fighting over her (even tho' she's not there and they can't see her!). What are the chances of persuading your neighbor to spay her cat? You're going to have to find some way to calm them down, but I don't know if Feliway has any effect in this situation, or if anything does... hopefully someone else will.

Have you taken them to the vet recently? If one is acting more strange than the other, he may be sick or slightly injured and perhaps is "being tough" as a cover.

Whether your neighbors cat is the cause or not, please encourage them to spay her. She will find a way to get out and a male cat will be waiting. Ellen Degeneres used to do a bit on how sneaky cats would be in attempting to get out or to gain access to a female in heat.

Thanks for the responses. I'm leaning toward it being the cat in heat causing this. It seems like it's caused by something he smells because he keeps smelling the air and has the flehman smelling look. He is meowing nonstop. Other than with our other cat, he shows no signs of aggression. Another idea is that maybe the neighbor's cat has attracted other cats acting territorial onto our property and he smells them too.

I have tried to talk the neighbor into getting his cat spayed before with no luck. I even got a voucher from the rescue groups for him. The response I get is something like "What's the point? She's indoor only. She won't run out, she's afraid of outside." Telling him that she is in distress, has a higher risk of health problems and could have kittens doesn't seem to matter.

If this is causing my cats to act like this I'm even willing to get her and get it done myself. It's been miserable, I had to lock them in rooms on the opposite sides of the apartment last night to keep them from fighting through the door. The aggressor won't stop meowing and pacing and my other cat is fuzzed up all the time and flinches when I touch him.

If this is a territorial issue, I'm becoming worried that they might start spraying even though they are neutered. Any advice on what I can do to calm them down in the meantime? (I'll probably get some feliway sometime today)


I'll probably take him to the vet just to make sure everything is okay, they're due for a checkup anyway.

Tis the season, or just about. Talk to your neighbor about possibly getting her cat spayed. If she is receptive to you and your advice. It would be better for her cat as well as yours. The Feliway will help as well, spray around the doors and windows and also get a few of the plug ins.

if your cats can smell her, chances are the local toms can too and might be peeing around your area, making your cats more territorial.

My Garfield is pretty jazzed up these days, and picking on his fur-sisters. All of them are spayed and neutered, but I have an intact foster who is nursing kittens.

Tell your neighbor that unspayed cats have a high incidence of uterine infections. I have a co-worker who had 3 sisters, and as they were inside only, she did not have them spayed. Two of the three died young from illnesses due to hormones. They can also have more cancer.

Hopefully this will all settle down soon as the neighbors cat goes back out of heat.

Some areas have laws that state you have to have your cat spayed/neutered in order to let them outside, you can call animal control and explain the situation, although I would use this as a last resort as it is harsh.

Just an update. It's day 3 and they still can't stand the sight of each other. Tonight my boyfriend and I tried reintroducing them. We used harnesses and gave them treats and lots of petting. We managed to get them within about three feet of each other before they started showing aggression. We separated them again immediately.

Buscemi (who seems to be the more aggressive of the two) is still acting strange. He is meowing nonstop and acting even more needy and affectionate (toward people) than usual. I got him some new toys to distract him and he will still play, but even when he is playing he meows like something is wrong.

Got comfort zone, but it doesn't seem to be helping.

I'm taking them to the vet on Wednesday to get them looked at.

The neighbor's cat just went out of heat, hopefully if that was the problem they'll start settling down soon. They also agreed to get her spayed if it was causing behavior problems with my cats.

I'm baffled how they could be so social with each other all their lives and suddenly want to kill each other one day out of the blue. Just waiting it out for now.

Originally Posted by enigma

Some areas have laws that state you have to have your cat spayed/neutered in order to let them outside, you can call animal control and explain the situation, although I would use this as a last resort as it is harsh.

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We both have indoor only cats. Unfortunately, I don't even know if it is the neighbor's cat causing it. It could be the tomcats she is attracting onto our property. Or, it could even be another neighbor's pet. I live in a big city without much room between my neighbors, so it's hard to pinpoint anything for sure if it's something they smell from outside.