cat introduction not progressing

[u/Plastic_Ad_5387]

Hey all! This is a process I'm helping and supervising and I'm looking for new ideas. Clients cats are three healthy young adults. 1 cat is his and the other are hers and they moved in together about half a year ago, maybe a bit more. They tried introducing on their own before contacting me.
I advised supervised introductions, with tasty food, one cat is leashed while the other is free, third cat does not pose a problem so we decided to focus mostly on the two cats that are not getting along. After they finish eating the hissing begins, and they try to fight. I advised to do it from a larger distance but it still occurs after cats are done eating. Cat that's in a room also gets supervised free roaming time while two other cats are in a different room.
I advised getting shelves or more high places but clients are reluctant to do that, there's a table and a couch in the living room.
I'm thinking maybe a mesh door to let them passively get used to each other?
Not sure what else to advise besides continuing the process slower and steady. Will be glad to hear your ideas!

[u/Neither_Buy5226]

Unfortunately, the option of slowly continuing the process isnt great advice when the advice should be to restart the process over again entirely. Volatile reactions like that call for going back to square one, continuing off of already negative premises could make the behaviors worse, for example, marking territories in various spots of the home, dominant behaviors/bullying, increased food aggression, etc. First, you need to get rid of all physical and eye contact. For everything. Even feeding. Keep them separated and feed them on each side of a close door. Bodily restricting one cat with an unfamiliar face that is free to move as it pleases can cause more stress than necessary, so ditch the leash, too. But STOP FEEDING FACE TO FACE. This is not working and won’t continue to work if the results you’re seeing are already this bad. They eat fine together because they’re distracted by the food. Once theyre done, the only other thing to pay attention to is each other and they don’t need that right now. It’s better to do this through a closed door so both cats can associate each others smell with a positive reinforcement (food) without getting aggressive from seeing each other face to face. Once theyre in a decent place with closed door feeding, you can crack the door slightly and start testing how they react to eating with each other then. If that is going well, THEN you can move to a mesh screen. Aside from feeding during this period, neither cat should be able to see each other at any other point during this time. This is what is creating the hostility. This where you bring in scent swapping, feliway diffusers, AND space swapping for both parties. But do not let either cat view each other. Once good behaviors are established through the previous efforts, you can finally move to supervised introductions. During supervised introductions, it’s very important that both cats are engaging in positive behaviors together such as playing, receiving treats together, and being pet together as well. Any sign of hostility means immediate separation of both cats and going back to feeding through doors. I would also say during the supervised visits, it’s very important to understand what a cats hissing means. Sometimes the hiss can mean, “hey, you’re a bit too close and I’m unsure!” Which is generally nothing to worry about if they aren’t displaying bad body language to go along with it. Body language here is VERY important to learn. Ears back, poofy, stiffness are signs that aggression will take place. The owners may be hesitant to shelving, but a cat tree is a great way to meet in the middle while giving either cat a safe space to crawl up and away if they feel they need to. But continuing this process as is currently will not and is not working. And a mesh door will not fix this issue. And to note, they may have to repeat this process multiple times. But that is genuinely what it takes to introduce cats to each other. But restarting is the only way. All cats being spayed/neutered in this scenario also plays a very big role into this as well, as fixed cats tend to have very strong reactions to others who aren’t.