I heartily agree about the possible health issue. Most often, especially if
the cat has been well behaved previously, a urinary infection can cause this
change in behavior. Males, too, have a particular problem if they develop
stones in the urinary bladder---very painful!
You see, the cat associates the pain it feels when trying to void with the
BOX ITSELF, that's why the change in behavior.
I know it sounds like alot to do, but after the vet visit (whether an
infection is found or not) try buying a new litter box (diff color, maybe?) and
maybe a new location to help him get over that 'pain association' thing he
might be dealing with. Certainly, talk to your vet about the problem, whether
you take the cat to be seen or not, mine is a great fount of experience and
information!
I have 2 females and only one litter box, but they are both very good about
using it, and there has NEVER been any confusion about where we do our
business. I HAVE caught both of them, however, digging at a particular "sweet
spot" on the rug. I don't know what the last tenant spilled there, but it
drives them crazy.
Is it possible your cat was first enticed to these spots by smelling
something there, too? You could have brought in something on a shoe or
something.
I know I've gone on a bit, but I hope something I've said helps. And, I
really hope you are able to cure him of whatever the problem is, so you can
keep him AND get new carpet to enjoy. You do seem like a concerned pet owner
and it would be a shame if you had to give him up!
Take care,
-Cindy