I agree to separate the two "suspects" first. As the first step has to be to find the culprit. Heck, keep EVERYONE separated until you find the right one! I know, that's not doable.

You are singling out males and calling this "marking." So let me quickly tell you what happened here this week:

Vita peed on a cat bed Wednesday evening, right in front of me. She has lived with me 9 years, never did such a thing. I was too shocked to move.

Thursday evening at about the same time, she marched into the Family Room where we are sitting, got on the blue cat sofa, turned, stood up on her tippy toes, raised her tail, and "marked" the sofa.

I was SO SURE this was behavioural, and due to Sugar's arrival 3 months back. But when I posted in Cat Behaviour, everyone (well, all 2 of them) said get her to the vet for a UTI check. First thing Friday morning I was on the phone, half an hour later Vita was unhappily providing a urine sample. (Needle couldn't get any, bladder was too small, so then she conveniently peed all over the exam table. The vet was laughing and saying "where's it all coming from? There wasn't ANY in there!" ) The vet said it was much too late for Vita to start reacting to Sugar - that jealousy or upset would have happened within a week of the dog's arrival.

Got the phone call late morning today. Vita has a bacterial bladder infection, crystals - not the struvite, the other ones, calcium oxalate. And her urine is more diluted than the vet would like. Her white blood cell count is high, and her temperature is low. We are using Baytril for 10 days, then we re test.

I'd never heard of a FEMALE marking, and wouldn't have believed it if I didn't see her do it!

This morning, Vita again marked a cat bed. She is slowly destroying all the pet furniture! I hope the meds take effect quickly.

Moxie and Decker have been with you, living large in the full house (not confined) for some time now. So based on what my vet told me, it is too late for that to be the cause of the upset.

I hope this helps.