My cat is suddenly attacking his sister

clary7

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I have 5 cats and the two oldest are siblings and 2 years old. The female is spayed and the male just got neutered a few weeks ago. Anyways, they got along great for their entire life so far. The girl is a bit skittish but never had issues with the male and she is not aggressive at all. She never initiates fights or conflicts when my other cats are being annoying. if there are problems, she just leaves the situation.

The male is suuuper friendly to all my cats and a super huge cuddler. He has never EVER been aggressive before to any other cats, even when he was intact. He was and still is just the chillest cat ever. He lets all my other cats cuddle with him and he is super relaxed around my dogs too. He would let my other cats when they were kittens to jump all over him and he is just the cool ‘chill uncle’ type of figure to them.

But about 6ish weeks ago I noticed him chasing his sister a little bit. He didn’t give any body language signals of it being aggression. It looked more like he was interested in her sexually (even though she is spayed) so I immediately got him neutered so he would stop bothering her. That was about 4 weeks ago. But since then, he has started actually attacking his sister. I’ve had a better chance to observe and it clearly isn’t sexual behavior like I first thought. He is also not showing any signals that he is unhappy before he decides to attack her. My other cats sometimes hiss, growl, or swat at each other if they are in a bad mood, but this male isn’t doing any of that at all. He isn’t even moving his ears back. His sister just minds her own business when he just looks at her and then jumps onto her and starts fighting. And he is not trying to play. Sometimes he sees her twenty feet away doing nothing and decides he needs to attack her so he runs to her and starts chasing her until she gets away or until he is able to attack her and fight. During meal times they don’t fight, but after they are done eating he sometimes attacks her while she just lays there relaxing.
It makes no sense at all. When he was intact, he was so friendly to his sister. But now that he is neutered he is attacking her. He hasn’t drawn blood but he does manage to pull out small pieces of her fur. I don’t actually know if neutering has anything to do with this since this behavior seems to have started right before he got neutered, so I don’t know if that is correlated at all with his behavior. I’m just confused as to what’s going on. I can’t separate them because they live outdoors not indoors, but we have a few acres, plus plenty of land around us that they hang out on (the land around us has no wild animals their size or larger. Just squirrels, rats, and similar types of animals. There are only a few other neighbors cats that have their own separate territory). So it’s not like there isn’t enough space for them. They have tons. I just don’t get why he suddenly has a problem with her after being fine for two years. I also don’t think it’s from a health problem because if he was redirecting due to pain, he wouldn’t be singling out his sister out of my other 3 cats, and he also wouldn’t be going out of his way to chase her down from across the yard for the sole purpose of attacking her. Plus when he got neutered the vet said he was perfectly healthy. I’m just so confused 🤦‍♀️ she never tries to fight with him. It’s always him attacking her without any warning.
 

susanm9006

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This is perplexing. It would be really helpful if you could get a short video of him interacting with her. In my mind it is one of two things. 1) He is actually playing, just in a very aggressive way or 2) Since they are outdoor cats, perhaps she is picking up some scent that he views as being strange or from strange cats and is reacting to that.
 

Mamanyt1953

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And at four weeks out, he's still carrying some male hormones, so that could be playing into it as well. It could still be mating behavior, even though she is spayed. It will be another 2-3 weeks before all of the hormones are out of his system.
 
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clary7

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I can't get a video because he does not attack her all the time, and when he does it's so sudden and out of nowhere that I don't have time to record it.

He's definitely not playing. He doesn't play with other cats unless they are kittens and initiate it first. And as soon as any of my kittens grew up, he stopped playing with them.

As for mating behavior, I also don't think it is that. I just checked the calendar and it's been just over 5 weeks since he got neutered. There was a female cat in heat that would come by about two weeks ago and he was completely uninterested in her. I've seen how he behaves around intact females when he was intact, and this is different.

I guess it could be some type of scent, that makes the most sense. If it is that, what can I do to help the situation? Is there anything I could rub on her maybe that would make him like her more?
 
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clary7

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No bleeding, but he does pull out tiny pieces of her fur. It’s not so much that she’s left with patches but when I pet her right after she has tiny pieces coming out.
 

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My girl does this with one of my boys. She's spayed and has known both my boys since she was 3 months old. One day a flip switched in her little brain and anytime she sees one of the boys outside (and only outside and only one of the boys) she just goes after him. And I mean trying to kill him go after him. Luckily, he is faster and not aggressive so he just runs to avoid her but we will find fur if she surprises him. But she has tried to kill him, I have seen her go after strange cats (and coyotes) she doesn't back down or play. She goes after him with the same energy. Funny thing is if she sees him inside the house she runs up demanding grooming and attention. Trust me, he is just as confused as the rest of us.

Got her fully vetted and nothing physical can explain it. Which left my vet saying it is something psycological. Either something happened that made her link him to something negative in the specific situation (he is a solid black cat so maybe a solid black cat attacked her and now she lashes out at solid black cats outsidebegore she realizes its her sibling, for example) or she just has something wired wrong in her brain.

So it could be something psychological, like the girl was nearby when something fell and startled him. So now he lashes out at her before *she* can startle him again? Usually it would take something more then a startle but really him mentally linking her to a negative experience (or reoccurring negatives) could cause him to lash out. Think a PTSD type response for cats. In which case, he needs to learn she wasn't the cause of negative either by having good experiences (treats only when she is there for example) to relearn that she is the source of happy instead of scary.

In my girls case, she will chase my boy and no amount of positive helped. So we went medication and corrective behavior. She gets a low level CBD dose to just take the edge off and anytime we see her go after the boy she gets scolded and redirected to something else. It has helped reduce the frequency of her attacks but not eliminate them. Which sometimes is all you can do. She at least doesn't attempt to kill him as much so baby steps in the right direction. My vet has offered psychological medications but pulling her would be a nightmare and the CBD is an oil I add to her food.
 
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clary7

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Ooh wow, that's pretty crazy. But that would make sense, that maybe something scary happened by his sister and he thought it was her. Thanks for sharing. If he doesnt stop attacking her after all his hormones are gone from neutering, then I'm guessing this explanation would make the most sense.
 

Mamanyt1953

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Also, since this is not a serious attack, or someone would be really hurt, the chances are that it is just play. To be honest, a LOT of play in kittens (and older cats) can look and sound like they are going to kill each other. That's because ALL play in felines (even the Big Cats) is practice for hunting. Small amounts of loose fur is normal. Big hunks with bleeding skin is not.
 
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clary7

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They are not playing. I have 5 cats and I know what playfulness looks like and what isn't it.

Yesterday the two were sitting next to each other. The girls back was to the boy and the boy was sideways to her. They were sitting peacefully not paying attention to each other until the girl looked at the boy and at the exact moment she looked at him he attacked her. It seems like maybe eye contact is what it triggering him.
 

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Hello! I think maybe he is bored. I have trouble finding ways to keep one of my girls entertained. She looks for trouble! She does this to both of her sisters, one is a littermate. She loves to hunt and stalk them out of the blue. If the other cats don’t run away.. I believe she wants the chase and doesn’t like them standing up to her, it turns into a showdown with hissing and claws may come out. Shes also horrible at just pouncing on them causing the two to roll with the others hissing and screaming. This can also snowball.. I think she gets over stimulated during these attacks at times which turn them into actual big fights. I think she just has so much energy to get out. Maybe this is happening with your guy.
 

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They are not playing. I have 5 cats and I know what playfulness looks like and what isn't it.

Yesterday the two were sitting next to each other. The girls back was to the boy and the boy was sideways to her. They were sitting peacefully not paying attention to each other until the girl looked at the boy and at the exact moment she looked at him he attacked her. It seems like maybe eye contact is what it triggering him.
Hello! How are things going? Your eye contact comment was interesting to me. Dealing with best friends/brothers who have been re-bonding since a redirected aggression incident In march. Things are much better but the random fights still kill me to see (they’re not playing). It is unpredictable and as if one looks at the other the wrong way and it’s a fight. Then they’re back to cuddling and grooming on the perch together. I know it is all good progress, but the random triggered event (eye contact/stalking) is driving me crazy!
 
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clary7

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I haven't seen them fighting lately but I can still hear it occasionally. The girl is still scared of being close to the boy and and now she hisses at him sometimes while eating which she never used to do before. I'm hoping they will sort things out out peacefully among themselves eventually.
 

sarapaps

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Thanks for your reply. It takes sooo much patience to get things back to normal it seems. It has been since March for us and id say things are 85% back to normal. I just hate to hear the hissing and even small fights when we never heard anything from them in 5 years!
 
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clary7

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2 month update:

It's gotten worse. Now the girl is super scared to be around her brother and runs away at the sight of him because if he sees her first, he always makes a beeline towards her and attacks her faster than I can intervene. He has made her bleed too on her nose at least once that I saw. They tend to still be peaceful while eating and will eat with their faces next to each other but if one of them looks at the other it turns into a fight.

I also think my younger male cat is seeing this and starting to copy the older male because now he is starting to chase her too occasionally, which I was not expecting because he has the personality of a teddy bear.

I am worried for her. Would it work if I made her a small fenced off space in the yard where the cats hang out and confine her to it so that they are forced to see each other and get used to being around each other again? She would be separated from them but be able to see them, just so I'm clear. Or will that only stress her out even more? She used to hang out on my property but now she runs away immediately after eating every day because she is scared of her brother. I'm wondering if I force her to stay nearby for a few weeks then maybe her brother will get used to seeing her and won't want to attack her anymore. But I need some advice on whether this is a good idea or not because I don't want it to stress out the girl so much that she runs away for good or something when I let her out again.

Also, she seems to be completely healthy but I have read that sometimes other cats could be aggressive because they are picking up on a hidden illness. I'm guessing either something scary happened around the girl that made her brother hate her, or she might be hiding an illness that he is picking up on. If it's an illness, what should I ask the vet to do? Are there certain tests they should do on her? Any time I've brought in a previous pet for a suspected sickness, unless the pet was actively dying or in danger they only do a physcial exam and then make me reschedule to another day to do tests. So if I know what to ask for ahead of time maybe I can ask them to do it while I'm scheduling an appointment so that I don't have to come back multiple times.
 

Alldara

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C clary7 Cats rarely, if ever work it out on their own. It usually just escalates. Her fear is building up because it hasn't stopped happening.

Usually bloodwork and a urinalysis is the basics. I would tell them in advance of the appointment that she needs these done :) But until a vet checks her over, you can know if she would need further diagnostics.

I think yes, building her an area in your yard for the time being would be excellent, or even inside a garage or shed if that's safe.
 

Kieka

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You might want to check out some my cat from he'll episodes too. Jackson Galaxy has some great scenarios with aggression between cats. You might be looking at needing to completely separate and reintroduce them from scratch. That is assuming you rule out medical issues.
 
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clary7

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You might want to check out some my cat from he'll episodes too. Jackson Galaxy has some great scenarios with aggression between cats. You might be looking at needing to completely separate and reintroduce them from scratch. That is assuming you rule out medical issues.
Could you direct me to some cat vs cat situations with jackson galaxy? I have watched a lot of videos of him but they are always cat vs human aggression and I havent come across any that were cat vs cat.

I also need some more advice. I made her a space to hang out in where she could be separated from the other cats but still in view, but she is probably the smartest escape artist ever and got out. So I had to put her in a dog crate but she absolutely hates it. Overnight she managed to break her litterbox into pieces. Today she is doing cartwheels all over the crate, spilling litter everywhere, and spilling water everywhere. She is best described as a semi-feral cat that only trusts me and sort of trusts my family, so any type of confinement makes her go insane. What I need advice on though is whether I should keep her in the crate or not since she is going crazy inside of it. Her brother tried to attack her a few times through the crate and I got to really see how they interact. It's come to a point that she hates him with all her guts and is growling, hissing, spitting, and everything else whenever he comes by her. He is less dramatic but I can tell he is on edge because he was redirecting some of his anger onto me and my other cats. By this morning though they seem to have calmed down a little bit. He isn't trying to attack her anymore and she is more calm when she sees him. So I think it might be working, except that she hates the crate. I just need advice on whether I should leave her in the crate and have her stick it through or if I should just let her out so she won't be stressed out, but also risk her not wanting to come home.
 
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clary7

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Well in case anyone cares for an update, I made her stick through it in the crate but also made sure to give her lots of attention. The first two days were bad. She was going nuts inside the crate and she and her brother were super angry that they had to look at each other. But it seems like forcing them to work things out what exactly what they needed. They are back to being 'friends' now, not in the sense that they like each other but they ignore each other now and are comfortable being around each other again. I hope things don't go south again, but I made sure the boy smelled her a lot so he would get used to her again, because I noticed some of his triggers earlier would be smelling her and then attacking. But I'm glad that this method worked for them.
 
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