Cat Digging other Cat's litter everywhere...

Hello- We have had mirabelle for a little over a month, Im sure some remember me talking about her- im wondering wether or not Otis, my 1 yr old resident cat will ever get along with her- He is just in a bad mood still around her- and his tail is always down now!

So last week i came home and found mirabelle's litter all over the floor- there was nothing in it however. Now, I caught him doing it again! Is this a sign of aggression? I know otis can be such a grump somtimes, we really like mirabelle and we dont want to give her up. Anyone have any suggestions?

I thought I would post one more thing- I just saw Otis pooping in mirabelle's litter box.

Does anyone think that feliway can help?

I think that Feliway is definitely worth a try. Also, cats often prefer 2 litter boxes, anyway, 1 for pee and 1 for poop, so it could be that Otis is claiming a 2nd box for himself - if you had added another box even without getting another kitty, he'd use that 2nd box. If at all possible, you could try adding at least one more box, and even add an alternative litter in the box, say clay litter if the other boxes have clumping. And locate the boxes in different locations, as well as the food - for some reason, that seems to reduce the tension level considerably (I think it has to do with a feeling of territory). You could also try to give Otis more play time, and maybe add some temporary "cat caverns" (I cut hole in large boxes - cheap, but the cats love it) - the newbies enjoy the hiding spot and/or the "locals" like the diversion of a new play area.
Sending {{{harmony prayers and vibes}}} to Otis & Mirabelle. And an exta cuddle for Otis :hug:

Thanks for your suggestions, I will definitely try them. We gave mirabelle her own box, and as soon as I get some more, I will give otis one as well.