Cat Sraying

We go through this with our cat whenever we move (fortunately, this will likely be the last time) and it lasts for a couple of weeks, even though he's been neutered. Cats do that when they feel they are under stress, which is likely with another cat in the house. Best thing is just to spend more time with him. The other possibility is, with two cats, the litter box(es) may not be as clean as your cat prefers. I know our cat will urinate on the first thing he sees if I forget to scoop his box nightly.

It is also important not to clean the areas with something that smells like Amonnia or this can trigger them to remark it as they may think the other cat in the house has marked it and mistake the cleaner scent with amonia as being the scent of cat urine.. - DNatureofDTrain