What about the cat that has stopped using the litterbox? There could be a number of reasons for this behavior. Some cats may not like the type or brand of litter that was put in the box.
Have you changed brands lately? If so, switch back to the brand you were using before the house soiling started. Remember that the texture and scent of a litter are two factors that can influence your cat’s reaction to it.
Some cats become upset if too much litter is placed in the box. Cats should be able to reach the bottom of the pan when digging. If you have one of these fickle cats, restocking the box with just a 1-inch layer of litter might do the trick.
Still other cats will refuse to use a litterbox that, in their minds, is dirty. Check your frequency of litter changes. If the litter is not being replaced every day, this could be the problem. If so, step up the frequency.
Also, do not use strong cleansers when doing your weekly litterbox cleaning, as the residual scents from these might be just enough to send your cat off searching for another place to do its business.
Refusal to use a litterbox may also be linked to some traumatic incident, emotionally or physically, that occurred while your cat was using the box on a previous occasion. Because of this, it now associates the box or its location with the unpleasant incident.
Obviously, the best way to find out if this is indeed the cause is to move the litterbox to a different location, one that is quiet and away from disturbances. For those cats that are especially emotional, buying new litterboxes might be required. Not all causes of house soiling are psychological in nature.
For instance, the presence of feline lower urinary tract disease can be the underlying cause of abnormal elimination behavior in felines. Since some of the diseases causing abnormal elimination can be life-threatening, always let a veterinarian rule out any medical causes before concentrating on behavioral causes.