Pooping next to box and getting aggressive

[jjsheiner]

We have a brother & sister 4yrs old from the same litter. They used to play nicely, cuddle and clean each other. My ex boyfriend moved in for about 6 months with his female cat and dog. My cats didn't really care about the dog but my female cat didn't not like his cat at all. He no longer lives with us but ever since then my female cat has gotten aggressive with her brother, hisses/growls when he comes too close, when he tries to play or chase she looses it. She's also going number 2 next to the litter box everytime but will always use the box to go number 1. She's also won't go to eat until her brother leaves the area. I'm currently recovering from leukemia and can't have her going potty on the floor all the time (it's just too dangerous for me) . I've taken both cats to the vet and they said there's no physical reason for her to be doing this. I've put out extra litter boxes but they will only use the same box and won't touch the others. I've tried moving their food bowls away from each other. I've tried cleaning the whole area around the litter box with an enzyme cleaner to remove any smell in hope that she wouldn't smell it and continue using the floor to go number 2. She's very friendly with our human family members but is aggressive enough with her brother that I'm concerned. She's never hurt him but definitely lets him know she dislikes him. I'm assuming it is some kind of behavior issue from when my ex's animals were living with us but I don't know how to help her. Please any advice is welcome!

[fjm]

Do you use a covered litter box? That might discourage her from pooping over the edge. If she continues even when the box is covered she may be middening - using her faeces as a territorial marker. Putting a large puppy pad or similar under the tray may make it easier to clean up until you sort the issue.

It does sound as if the introduction of a strange cat into her home has triggered a lot of anxiety and possibly redirected aggression. I would feed the cats in separate rooms, if that is possible, and make sure there are plenty of beds and high spaces for them to be apart from each other. Some people find hormone diffusers like Felliway helpful, for others they make no difference. Unless she is actually attacking her brother and drawing blood I would not worry too much about his safety - cats tend to posture and curse a lot in order to avoid actual physical contact. I would concentrate on making both of them feel safe, secure and loved, reassuring her that this is her home and rebuilding her confidence - getting cross with her for either the pooping or the aggressive behaviour is likely to be counter productive and just make her more anxious. You don't say how long it is since your boyfriend and his animals moved out, or for how long she has been behaving this way.

[jjsheiner]

I'm using very large uncovered boxes. I never get angry with her about it, just sad that she's so upset that she's doing this. My ex has been out of the home for about 7 months. A vet just suggested giving her cbd oil for pets and or trying feliway. At this point I'm willing to try anything that might help. Thank you for your suggestions.