Why Is My Cat Suddenly Fighting With Everyone?

Dear Most Esteemed and Knowledgeable Kitties:

I have five cats, four females and one nuetered male. All have been introduced at different times over the past three years. All of them have gotten along just fine. Niko is my second oldest and female. Over the last month or so she has begun hissing any time one of her sisters walks nearby her or tries to play. It has even resulted in one actual fight. She has never acted this way and its frightening. All the other cats are acting normal. Why all the aggressive behavior all of a sudden? She won’t socialize and won’t quit being mean to everyone. She used to be so playful with the others. Why is she doing this?

~ Jeremy

an angry Sphynx cat hisses.

Angry Sphynx cat, (CC-BY-SA) by Wikimedia user Trilobite2

Siouxsie: There are two common reasons for sudden behavior changes, Jeremy: health issues and redirected aggression.

Thomas: Redirected aggression comes from seeing an intruder outdoors and not being able to do anything about it — which makes the cat attack the first indoor thing she sees.

Bella: But Jeremy, we suspect that your Niko might be acting aggressive because she’s in pain or because she’s ill.

Siouxsie: You see, we cats instinctively hide our pain. It’s encoded in the core of our very being because showing pain means weakness, which could get you killed out in the big, bad world of wild cats.

Thomas: Because of this, the only sign you might have that your cat is hurting is a change in her demeanor and the way she acts toward you and other cats.

Bella: For example, Siouxsie gets grumpy when her hips hurt, which means she’s grumpy all winter! Tee hee hee …

Siouxsie: Listen, you little runt, you’d better cut that out right now or I’ll come over there and swat you!

Bella: Oh, sure you will. If you can get those creaky bones to run as fast as me! Nanny-nanny-boo-boo!

Thomas: Bella, you cut that out. You’re gonna be old and creaky someday, too, so respect your elders!

Bella: *grump*

Siouxsie: Anyway … as I was saying before I was so rudely interrupted: I recommend that you take Niko to the vet for a checkup.

Thomas: Me too. You should probably get her a blood test, too, just to make sure she doesn’t have anything wrong with her liver, kidneys or thyroid gland.

Bella: If you do find that she’s in pain and you’re able to do something about it, I bet she’ll start feeling better (and being nicer to her feline housemates) pretty quickly.

Siouxsie: On the other hand, if Niko gets a clean bill of health, you’re going to want to look into redirected aggression as a possible issue.

Thomas: Your vet will probably have some tips on how to help her feel less stressed, which will reduce the aggression.

Bella: We’ve got some tips on the subject, too, which you can find here and here.

Siouxsie: Good luck, Jeremy. Please get back to us on what you find out — we’d love to get an update on Niko and how she’s doing.

  • Jilla

    Oh Bella-Boo…what are we gonna do with you??

    • Belladonna Moonshadow Kelley

      Well, play with me, of course! You must have a feather toy handy!

  • vagabond

    Bella- you are quite the saucy wench!

  • Anita

    Jeremy, I hope you find our your kitty’s problem very soon. I have a 16 year old kitty (lLittle Bit) who, at the age of 14, became very angry with his siblings. He even growled while he ate and snapped at them if they came around him. I know something was wrong and then I noticed he had lost weight. Turned out he had to have teeth removed. Two surgeries later, he is the old sweet kitty he was (although athritis has him whinning sometimes). I suspect your kitty doesn’t feel good and doesn’t want to be bothered with the other kitties who do. Niko needs blood work, etc. to find out what is going on. Be patient with her. If only she could talk…

  • Gail

    Hi Jeremy
    The Most esteemed kitties are right.
    This also happened to my furbaby, Sassy.
    Sassy and Muffin (her brother) were snuggle buddies. They always slept together. Then suddenly for no reason Sassy virtually lost the plot. She hated Muffin, she actually had a down and out fight with him. I got concerned and took her to the vet. So yes, as I said earlier, the answer the furbabies gave you is 100% correct. Take your little Niko to the vet and have her checked. I had also sent a similar question through and followed up on their advice and they were 100% correct. So please, Jeremy, do it as soon as possible, PLEASE! Because I didnt ask for advise of the “kitties’ earlier… well, I really dont want to say….sorry..so please just DO IT! They and their mama, oh, so definately know what they are talking about.

  • http://trupanion.com/ Jackson

    Hear, hear. I’ve experienced both. I have one cat who goes insane at the approach of visitors. She’s the only cat I’ve ever had who hisses at strangers. When she’s in this mood, my two other cats don’t dare approach her. Sometimes when I order pizza, she gets so worked up about the delivery guy, she attacks whatever is nearest her. Not sure why she’s soooo territorial or distrustful of visitors. Ironically, when her redirected aggression suddenly stopped last year, I immediately suspected something wrong. Turns out she had a growth in her repro parts. Once removed, she was A-okay all around. Very sedate. I think the strange people agitated her illness, until all the aggression wiped her out.