Sister Cats not Getting Along

Question
I have had two sister cats since their birth, and they have lived with me together since.  They are now about 2 years old and they are not getting along recently.   They are both outdoor cats and have always come inside as they please.  About 6 months ago I also got a dog, who they both did not get along with well, but after some time and training the Dog, they are ok with the dog (i wouldn't say they are best friends, but they are not afraid to come inside).   Everything was going smooth until a few weeks ago when one cat just wouldn't come home and the other cat just stays inside.   I had to chase the cat who wouldn't come inside around the neighborhood and grab her to get her to eat.  She is now inside with her sister but she hisses at her sister and they don't seem to be getting along.

I've also remodeled recently and had to reduce from 2 littler boxes down to 1 large one.   Is this the cause of the issue?  I did that about 3 months ago, and they seemed fine with it at first.

Any thoughts?  I appreciate your help and I love my girls

Thanks!
Andy P

Answer
Andy,

Cats are creatures of habit and do not do well with change.  It sounds to me as if too much has changed and they are having trouble coping.

Cats can get incredibly territorial about litter pans, so I would try to find a way to go back to two litter pans.  Then you will just have to see if they adjust after a few weeks.

You may also want to consider making them both indoor cats and give them plenty of time to get along.  Upon doing this you may need to put one litter pan in another area of the house.  One caveat is that some dogs think cat poop is candy and will even bother the cat trying to do its business, so having at least one litter pan where the cats can get to it, but the dog cannot may be helpful.

Please let me know how it goes.

Best regards... Norm.