Cat behavior issues - siblings fighting

I’m looking for someone who can help diagnose and resolve cat behavior issues.

I have two male orange tabbies (siblings) who have been together since they were kittens. Now, 8 years later, they’re suddenly fighting constantly and can’t be in the same room together. The usual suspects in a case like this are illness or change in environment but they’ve both been checked out by the vet and nothing in the house has really changed in the last couple years.

Can anyone recommend a specialist in cat behavior or even a good vet who would be willing to do a more detailed medical checkup?

I’ve heard of this happening. Did you happen to take one to the vet without the other at some point? Has your schedule changed recently? Is your apartment particularly small? Anything else that could be stressing them out?

Not that I can think of. They’ve been separated and slowly reintroduced a couple times already without improvement.

A change in scent is a possibility. One of them pees everywhere when they get into a fight and it gets on both of them, along with the furniture, walls, me…

Could be they’re just getting older and their body chemistry is changing such that they are no longer able to properly recognize one another. There are resources online describing how to reintroduce cats, but it’s quite an involved process that will require time, resources, and concerted effort on your part.

What have you tried so far? Also, paging @Icon

That’s a good theory. The younger has been territorially aggressive toward other cats, except for his brother. If he’s mistaking his brother for another cat it could cause issues.

I’ve tried separation, feeding them on both sides of a door and then eventually together, play separately and together, Feliway pheromones, adding another litter box, food bowl, and fountain, swapping rooms and short supervised visits to exchange scents.


Damn it sounds like you’ve tried it all. My friend did the same and had to just rehome one of her cats when she couldn’t make them get along anymore…

Perhaps consider clicker training to positively reinforce the times they exhibit nonaggressive behavior around each other? Cats can be fairly responsive to it.

I haven’t tried clicker training in particular, but do reward them when they’re behaving well together with praise, catnip, and food.

Rehoming one of them is really a last resort. I know being siblings doesn’t really mean much to the cats, but I’d hate to have to break them up. Plus they get really lonely when they’re separated.

I’m hoping there are behavior specialists in Taipei that can come take a look at the cats and their environment and give ideas. Or maybe a vet who specializes in behavior issues and would be able to do a more behavior-focused medical check.

Tooth problems are a likely culprit, as it is a very troublesome but hard to detect health issue. In Xindian we have a pet dentistry specialist, right next to Xiao Bitan station. You could try that.

NTUVH has a psychiatric consultation, must bring cat pee sample to rule out infection.

I also know of at least two certified cat whisperers, if anyone wants to I can put their data here, if I haven´t yet. They do make home visits, most vets I know of don´t.


This article talks about a potential danger that is easily overlooked in our homes. Those scented satchels, this Farcent thinghies we put in the bathroom, anything could be upsetting your cats´health and behavior:

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How bad are the fights? Are they drawing blood? Or are they just fighting to the point where one hisses and eventually leaves the scene?

That’s also a good suggestion. One of them has had serious dental issues in the past and has had several teeth pulled already. The vet did take a look and said he didn’t see any signs of serious tooth issues, but a specialist might be worth a visit.

As for cat psychiatrists and cat whisperers (I’m assuming that’s a cat behavior specialist?), any specific recommendations you can provide would be appreciated.

We don’t have anything like that in the house.

Yes drawing blood. And they’ll continue to fight until I break it up.



Do the fights often start at a few fixed locations? If that’s the case, perhaps you could setup a way for one of them to move through those areas from higher up?

Serious fighting is a bad sign

You may have to split them up

We have three indoor and outdoor strays that we are rehabbing
One of the strays fights with our cat while the other two do not

We keep our cat in our bedroom separated from the living room with one of those child doors with bars when the non conforming stray is in the house

Physical separation was the only thing that worked

Our cat whopper had attacked this young cat several times when he was a kitten and now that he’s about ten months old he is attacking back

Bad blood beteeen them means no unsupervised being in the same room

Even though no blood drawn just some ruffled hair

It’s been Months and they are not going to be friends

Frenemies for life

Not that I’ve noticed.

I’d like to avoid this if possible. If it were two strange cats who never had a history of getting along maybe, but these are siblings who lived together for 8 years without issue. If something’s changed in either the cats or their environment lately then I’m hoping it can be identified and resolved or at least accommodated.

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Sibling relationship in cats like they do in humans may lessen often as we age .

This is probably too obvious to mention, but you didn’t happen to bathe/wash them recently I suppose?

No, I never bathe them.

Maybe you have one stinky cat and one delicate cat