Why did my sweet cat suddenly attack his brother so aggressively?
Updated On September 23rd, 2025
Pet's info: Cat | Maine Coon | Male | neutered | 13 lbs
I have two 3 year old male cats and they were both laying down next to each and then all of a sudden my one cat Kia starts aggressively attacking his brother. He’s normally very sweet and mellow. What could be the cause of this sudden behavior change?
2 Answers
Most Helpful Answer
Published on November 7th, 2017
I'm sorry you had to experience that. Instances like this are always pretty stressful. Unfortunately, many times instances such as this are not going to be figured out entirely. If they were truly just laying completely calm and then there was a sudden abrupt attack, my best guess is that one of the cats could have been startled by something and then redirected its aggression to the nearest living thing, which in this instance was the other kitty. I would obviously continue to monitor the situation closely for any repeats. If this occurs, you may have to consider separating them for awhile while you examine other possible causes. This may include medical issues (particularly any one that might be painful to one of the cats), resource guarding, or intercat aggression due to dominance behavior. Hope this makes sense.
1Pet Parents found this answer helpful
Related Answers from Veterinarians
-
Published on November 1st, 2018
Cats are frustratingly subtle with their early signs of aggression and really anything can they find upset can permanently damage a relationship. So it's likely that something happened between the two of them that you missed, that led to the early aggression that you couldn't pick up on, but now it's more obvious. So this has probably been going on for weeks or months, even though it looks sudden to us humans. The incident could have been one of them going to the vet or otherwise leaving the house, one of them being slightly ill, something scary happened (vase falling over, washing machine starting, big truck going by on a day it was also thundering outside) when the two were together that they associate with each other now. That would be my best guess about what is going on. I hope that helps you think through it.
1Pet Parents found this answer helpful
I have 5 cats; three males and two females (all fixed). All grew up together and have always been nice to one another. About 2 months ago bubba has started terrorizing one of my female cats. Vet says he is in good health. Behavior is random and not l
Why have my cats (who are sisters) suddenly turned on each other and viscously started attacking the other one?
We have three cats in a 2 bedroom apartment. We have had the 2 of the cats for 3 years and the other one for 2 years. One of the older cats, who has always been docile and nice has recently turned very mean to our younger cat. She has not let her out
My two cats have been fighting recently and we are stressed out. They are brothers and are about ten years old. They have always gotten along so this is a rare occurrence. The oldest is blind in one eye and has always been the alpha. We really need s
My other cats (4) are attacking only one particular cat. They have never been aggresive to him before until now. They are so mean to the point they try and attack me when I separate them. This has never happened before I am not sure what to do. I sep
I have two brother cats, since they were 2 mos old. They are 3 years old now. Just this morning, first time ever. They started hissing, growling and puffing up at each other. I examined each one and neither seems to be having any kind of pain or obvi
My cat is acting very aggressive all of a sudden. Going after our other cat for no reason. It all started after we put a new flea collar on the cat she is attacking. We took it off and even gave him a bath to rid of any smell but she is still attacki
You I have a cat that is roughly 10 yrs old he is a Male few months ago we got another older female cat both are fixed..recently our Male cat has been attacking our female I mean really attacking her...I am worried that there maybe could be something
I have two cats. One I got when he was 2 months and a year later I got a cat that was 2 years old. At first I had to keep them in separate rooms until I was able to introduce them to one another without the aggression that was first experienced. Now
Hello, our cat is a 4 years. He is the friendliest suck. My husband works from home and is the main care giver, feeds, grooms, plays and cleans his box. They are buddies. As of late he has tried to attack my husband for no reason. He came home pet hi
Book an appointment with the pros – our expert vets are here to help.
