New - Hissing/growling/attacking Brother Cat

[EricDufficy]

We have 2 lovely boy orange cats who we adopted together (same litter) 5 years ago - Tuna and Tomato. For the last 3-4 years the cats got along great. They slept together, bathed each other and would both love to be in the same room together. Over the last year Tuna has started to hiss/growl at Tomato if he is anywhere near him. He sometimes lunges at Tomato slapping him in the face. Tomato, although a bit bigger of a cat rarely retaliates and timidly leaves the vicinity or moves out of the way. Sometimes it escalates into a full on cat fight with fur flying. It has really been bothering me and I wish we could go back to when the cats got along. Does anyone have any ideas for me?
Some things to note:
Both neutered.
When they used to play fight, Tomato usually dominated as he is a bit bigger of a cat.
Kids in the house, age 2 and 4. (Tuna LOVES the kids and never hisses or growls at anyone but Tomato)
We have had to move 3 times in the last 5 years.
The cats used to be strictly indoor cats, then started going out on the deck, then when they discovered how to escape became indoor/outdoor cats (mostly indoor). If I recall, Tuna did get a tad territorial after they had their first taste of outdoors a couple of years ago.
Tuna seems territorial over laps and human contact.
They share a litter box an dry food bowls nearby. They get wet food in the evening and eat close together but never fight over the food (our place isn't that big).
I have considered talking to the vet about giving Tuna CBD oil to chill him out. Anyone with experience regarding this?

I would love some advice. Thanks for reading.

 

[PassifloraFoetida]

Oh no! It sounds like it has been super stressful for both your family and your cats. I'm in no way a cat behavior specialist, but if you haven't already, it might be worth getting Tuna in for a checkup just to rule out any potential health issues that could be causing a shift in his behavior. If he isn't sick or hurting, your vet could potentially give you some advice on how to curb the aggression.

In the mean time, some environmental things that have helped in our multi-cat household may help in yours. We use a plug-in feliway diffuser for multiple cats to help keep general tension down among our herd. I also realize you mentioned having a small living space to work with, but it could help to try to minimize the need for territorial behavior by increasing the number of various resources, if you haven't already. Multiple litter boxes in different parts of the home, multiple high sleeping spots/cat shelves/trees, dry food and water in a couple different spots. You can try to do this with any resource that could cause a conflict to start and see if that helps ease a bit of the tension.

If Tuna is specifically acting territorial over people and affection it might do to try reconditioning him, in a sense. We've had a lot of luck with positive reinforcement, and we did something similar to this when we introduced our third cat to the group and our existing cats were somewhat skeptical and standoffish. We started pretty broad, separating the cats and slowly reintroducing them in stages over the course of several weeks while doing things to make the experience positive for everyone. You may not have to go quite so extreme since they are familiar with each other, but you can try offering Tuna positive reinforcement/treats when he doesn't act territorial toward tomato. If tomato is having a snuggle and Tuna is nearby, have someone reward Tuna for staying calm or talk softly to him/play with him. If Tuna's favorite person approaches Tomato for a snuggle or a pet have someone else give Tuna a treat or play with him a bit to associate that action with a positive experience for Tuna. If Tomato will tolerate it and they eat within line of sight of each other, have someone stroke him while he eats or hold the wet food while he eats so that he has to be in their lap to eat it. It could help to further associate the positivity of food time with Tomato receiving attention. Keeping them a bit distracted or busy around each other could also help. If they're food motivated, you can maybe try some trick training to help keep them entertained and work out some of that extra energy so they're content and sleepy while inside. You can do the same thing with play if they show interest in that.

I don't know if any of what we did will work for you, but I hope you have some success with your boys.

 

[jen]

Agree with above but I think Tomato should be the one to get a check up. Cats will lash out at sick cats in the group. We all know cats don't show there is anything wrong until it is serious. When cats don't feel well they smell different.

To be honest, I would just have them both checked out. I mean bloodwork, fecals and urine, not just a quick exam. When was their last yearly check up?

 

[PassifloraFoetida]

Jen is totally right. I'd completely forgotten about that tendency in cats when I drafted my response. I would vet them both.

 

[EricDufficy]

Thank you very much for the replies and the suggestions. Very appreciated. I will come back and let you know if anything works!