Sudden aggression in one of my cats

xSimonDavidx

TCS Member
Thread starter
Kitten
Joined
Jan 25, 2021
Messages
6
Purraise
5
Hey, everyone! I have my certificate in veterinary assisting, and I worked as a Vet Tech for a few years, but I’m still at a loss on this one. I rescued my cats about three years ago, they’ll be six this summer. They are both spayed females, and they are from the same litter, so they’re actual sisters. Ever since I’ve had them, they have been completely inseparable. They sleep together, eat together, cuddle together, and when one of them can’t find the other, they’ll run around the house howling until the other comes running.
All of the sudden, one of my cats started hissing and growling at the other one. My gut instinct was that she was either in pain, or sick. She doesn’t have any signs of illness, and she’s not showing aggression towards the dogs or people. Not to mention, her aggression with her sister is very on and off. Yesterday they were fine all day, cuddling and everything. This morning she started hissing and growling at her again, then was fine a couple hours later, then went back to being aggressive. I started thinking a possible UTI, or bladder stones, which could cause aggression when she was in pain, so I brought her into the vet. She was given a shot of some antibiotics and a pain reliever, and they sent her home as they were unable to get a urine sample for a urinalysis. There hasn’t been any physical fights, which I’ve been glad about. She won’t even let her sister near her when she gets into one of her moods. She’ll walk into a room, see the other one and immediately start hissing. However, the other cat is completely un-phased by all the hissing and growling and will just sit there and stare at her until she gets bored and walks away. Does anyone have any idea of what might be going on? I don’t know what to do at this point. Thanks, everyone.
 

Attachments

FeebysOwner

TCS Member
Top Cat
Joined
Jun 13, 2018
Messages
13,223
Purraise
17,594
Location
Central FL (Born in OH)
Hi. The only thing that comes to my mind is an outside animal roaming about that is disturbing your one cat and creating re-directed aggression (see article link below). If not an outside source, and you live in an apartment with people below or above you, there may be noises/sounds that are causing the same effect.

You also still need to get a urine sample so you can definitively confirm or rule out a UTI or other urinary tract related issue. Have you considered getting a urinary collection kit and obtaining a sample on your own to take to the vet for urinalysis? Even if she were to have an infection, a urine culture, along with the urinalysis is the sure fire way to guarantee the right antibiotics are being given to her.
Re-directed Aggression In Cats – TheCatSite Articles

Hope other members will come along soon with some other ideas!
 
  • Thread Starter Thread Starter
  • #3

xSimonDavidx

TCS Member
Thread starter
Kitten
Joined
Jan 25, 2021
Messages
6
Purraise
5
Hi. The only thing that comes to my mind is an outside animal roaming about that is disturbing your one cat and creating re-directed aggression (see article link below). If not an outside source, and you live in an apartment with people below or above you, there may be noises/sounds that are causing the same effect.

You also still need to get a urine sample so you can definitively confirm or rule out a UTI or other urinary tract related issue. Have you considered getting a urinary collection kit and obtaining a sample on your own to take to the vet for urinalysis? Even if she were to have an infection, a urine culture, along with the urinalysis is the sure fire way to guarantee the right antibiotics are being given to her.
Re-directed Aggression In Cats – TheCatSite Articles

Hope other members will come along soon with some other ideas!
Thank you so much. I definitely plan on taking her into the vet again and having them attempt a cystocentesis to get her urine sample. Last time they had just tried pushing on her bladder and couldn’t get anything. I live in a house, so there’s nothing weird going on. We do have a couple stray cats around, but it doesn’t seem to be coming from an outside source.
 

FeebysOwner

TCS Member
Top Cat
Joined
Jun 13, 2018
Messages
13,223
Purraise
17,594
Location
Central FL (Born in OH)
We do have a couple stray cats around, but it doesn’t seem to be coming from an outside source.
I wouldn't entirely rule this aspect out. You may not be aware that an outdoor cat is nearby, but that doesn't mean your cat can't sense it. Nor does it mean that if it bothers your one cat that it will automatically bother the other one. I'd be keeping an eye outdoors when she starts to act up, just in case you might catch site of some animal in your yard. I would also go outside and check around for urine smells, such as a cat spraying around your home.

There is a reason for her intermittent behavior. And, while a urinary tract issue can create pain, it would more than likely be more consistent, or at least more correlative to around the time she uses the litter box.
 

Furballsmom

Cat Fan especially Black Cats
Veteran
Joined
Jan 9, 2018
Messages
28,588
Purraise
38,897
Location
Colorado USA
I agree with FeebysOwner FeebysOwner in that there very likely is something external going on that's causing redirected aggression.
I'd suggest setting up a camera or two outside so that you can see what's happening.
 
  • Thread Starter Thread Starter
  • #6

xSimonDavidx

TCS Member
Thread starter
Kitten
Joined
Jan 25, 2021
Messages
6
Purraise
5
I wouldn't entirely rule this aspect out. You may not be aware that an outdoor cat is nearby, but that doesn't mean your cat can't sense it. Nor does it mean that if it bothers your one cat that it will automatically bother the other one. I'd be keeping an eye outdoors when she starts to act up, just in case you might catch site of some animal in your yard. I would also go outside and check around for urine smells, such as a cat spraying around your home.

There is a reason for her intermittent behavior. And, while a urinary tract issue can create pain, it would more than likely be more consistent, or at least more correlative to around the time she uses the litter box.
Yeah, I’ll definitely look into it. The only reason I said I didn’t think it was from the cats outside is because the strays that come around make my other cat aggressive, not the one that’s currently acting aggressive. Since my other cat isn’t acting aggressive, I figured the strays haven’t been around, because it’s been super cold.
 
  • Thread Starter Thread Starter
  • #7

xSimonDavidx

TCS Member
Thread starter
Kitten
Joined
Jan 25, 2021
Messages
6
Purraise
5
I agree with FeebysOwner FeebysOwner in that there very likely is something external going on that's causing redirected aggression.
I'd suggest setting up a camera or two outside so that you can see what's happening.
Yeah, I’ll look into it. It’s gotta be something. She’s just never been bothered by any strays or anything before, that’s always been my other cat, and even she hasn’t been acting up lately, because the cat that normally comes into our yard, hasn’t been around due to the cold. But I know there has to be something. It is common for female cats to suddenly realize they don’t like each other anymore, but it’s not as common with litter mates.
 

ArtNJ

TCS Member
Top Cat
Joined
Jun 1, 2017
Messages
3,774
Purraise
4,267
I think that sometimes if one accidentally hurts the other during playing, that can trigger problems.

Have you tried a short separation (full isolation of one in a room) to reset things?
 
  • Thread Starter Thread Starter
  • #9

xSimonDavidx

TCS Member
Thread starter
Kitten
Joined
Jan 25, 2021
Messages
6
Purraise
5
I think that sometimes if one accidentally hurts the other during playing, that can trigger problems.

Have you tried a short separation (full isolation of one in a room) to reset things?
We’ve separated them during the night, so they’re not together unsupervised, and then they’re okay when they wake up, and then throughout the day the other gets aggressive on and off again. I did order a calming diffuser that should be in tomorrow or Wednesday, and I’m hoping that’ll help some.
 
  • Thread Starter Thread Starter
  • #10

xSimonDavidx

TCS Member
Thread starter
Kitten
Joined
Jan 25, 2021
Messages
6
Purraise
5
I’ve started using a calming diffuser that is supposed to mimic their mother’s natural pheromones. It’s only been a little over a week, but after the first 3-4 days, I could see a huge difference. She’ll still hiss at her sister every now and then, but it’s been once every couple days or so. She’s dramatically improved, so I’m hoping she’ll start doing better.
 

Katy Perkins

TCS Member
Young Cat
Joined
Jan 14, 2021
Messages
33
Purraise
15
A couple of possibilities are that it could be sick and/or in pain. Illnesses and injuries are not always visibly evident in cats as they have a high tolerance for pain. If it’s strictly an indoor cat, it could be due to another cat it has seen, heard, or smelled outside. It may feel threatened by it, but since it can’t get to it to defend its territory, it will transfer its aggression onto someone else. Also, cats are creatures of habit. They generally do not respond well to change as it causes them a lot of stress.
 
Top