While there is obviously no question who is not using the box if you only have one cat, when you have two or more, finding the culprit could take a bit of sleuthing.
You may have a fairly good idea of who the malefactor is, and a trip to the vet to rule out a medical problem is the first step – if you only have two cats, take both, otherwise stick with the most likely candidate to begin with.
Pinpointing the Culprit
Finding out which cat is urinating and defecating other than in the box is not an insurmountable task, and here are some hints that will help you find the culprit.
A nanny cam, set up near the scene of the crime (remember the criminal often returns to the spot) can show you who exactly is not using the box.
Small cameras that attach to a cat’s collar can also help. These won’t show the actual deed, but will show the area where the cat has been eliminating.
The cats can be sequentially isolated from the rest of the clowder, which will show the box-avoider by a process of elimination.
Your vet can give you a harmless dye that will show up in your cat’s urine when using a black light lamp.
If pooping is the problem, you can put some small pieces of red or yellow crayon in the suspect’s food, but only when given the go-ahead by your vet.
Overcoming the Problem
The problem can simply be that there aren’t enough boxes for the number of cats; each cat should have his or her own box, and there should be an extra as well.
If a dominant cat is causing the problem, place the target’s litter box at some distance from that of the top cat – usually moving it gradually is the best approach.
A cat that has been declawed will often experience heightened sensitivity in the paws.
Your choice of litter might simply have been too harsh, and often a softer litter will solve the inappropriate elimination.
Changing the type of litter box could also have a positive effect. Some cats don’t like enclosed boxes, and some are afraid of motorized boxes.
Litter box liners can also bother cats, so if all else fails, get rid of the liner. And, always make sure that the box is clean; no cat likes to use a box filled with feces and urine-soaked litter.