7yr old siamese aggression & urinating

Question
Hi Madonna, this is quite a lengthy question, but here goes: in January last year we introduced two 4 month old Maine Coon sibling kittens to our then two 6 yr old Siamese cross females (sisters). All 4 cats were spayed as kittens. There were some problems with the introduction and the female Coon, who was the runt of the litter, was always being picked on by one of the adult Siamese (T). These fights would get very noisy and lots of fur would fly! The 2 Siamese seem to cope okay with the male Coon (he is now twice as big as them) as he doesn't really react to any of their aggressive outbursts. However, one of the Siamese (call her T) began urinating on the kitchen benches, beds and lots of other places! We have taken her to the vet several times and have tried Prozac (which worked initially but she was so stressed about taking the medication that things got worse) and the Feliway plug-ins. We now separate the female Coon from both Siamese at all times, staying in our bedroom during the day and coming out at night when the Siamese girls come in to sleep with us. The male Coon goes where he wants! Recently, T (the Siamese) has started urinating on clothes and table tops in our bedroom at night even though there is a clean, covered litter box there for her to use. When it was raining for several days, she urinated on the dining table (!!!) and on the floor because she couldn't get out into the garden to go, again even though there were 2 other clean litter boxes for her to use. She is also now more aggressive towards her sister (the other Siamese C) and 2 days ago they had a full on fight, which they have never done before. What can I do? We have tried so many things and the vet has told us they can't do anything more. Our little household is now so stressed because of this aggression and inappropriate behaviour, and as neither of the Siamese have coped well with the introduction of the female Coon, I don't know what we can do to improve the situation. I would like all 4 cats to be able to wander freely inside our house and out into their huge outdoor enclosure! I am really hoping that you have some ideas. Sorry for the really long question, but this has been going on for almost 18 months now and our stress levels are very high! Kind regards, Cheryl. PS: I am in Australia and therefore may not be able to get some of the products that I have seen recommended on this site.

Answer
Female cats, once fixed, tend to get along with male cats better than other females.

It seems to me that T needs to become an outdoor only cat, with brief times inside. She clearly feels that her territory has been invaded and is displaying aggressive scent marking behavior. Since she is already partially an outdoor cat, the transition should be easier for her. I suggest getting a doghouse with a catnip blanket at the bottom for her bed and a litter pan next to it as well. When it rains, bring the cat inside with that same litter pan, and do not let any other animals use it.

Spraying can be an infuriating, frustrating problem with few answers. If the feliway isn't working, it's clear that typical chemicals won't affect this feline. Get her outside into her own space, and she may cease the marking on her own after a while.