This is a question about “inappropriate elimination”. That’s a euphemism because from the cat’s perspective the elimination is appropriate because he or she is probably anxious, fearful and stressed because of a specific reason. Anxiety and fear are often the main factors driving cats to defecate indoors outside the litter tray.
Dr Bradshaw in his book Cat Sense, writes that some cats defecate on their owner’s bed sheets in a desperate attempt to try and mingle their own odour with their owner’s to establish ownership of the ‘core of the house’. Both bed sheets and bathtubs smell of the cat’s owner.
I can remember my former wife’s cat doing just this. She was absent for long periods from her flat. Her cat was stressed because of this absence. Perhaps it was separation anxiety. I think we can say with some confidence that anxiety is the most common cause of a cat pooping in the bath tub.
So what’s the solution? Well, the owner has to find out why their cat is anxious. It may be a cat outside coming inside the home. Or there may be disputes within a multi-cat household. Those are the usual causes.
There may also be feline medical reasons but this is much less likely. Another possible cause would be that the litter tray is in the wrong place, badly maintained or shared. However, the most likely cause of anxiety in domestic cats is quite possibly the worry that their territory is going to be invaded by other cats. These ‘invading’ cats might be in the neighbourhood or inside the house.
Dr Bradshaw did a survey in 2000 in rural Devon and in Hampshire, UK. Half of the 90 cat owners reported that their cats regularly fought with other cats. 40% of the cats were fearful of other cats in general. The point being made is that there is a lot more anxiety amongst domestic cats than many cat owners realise and one symptom is ‘inappropriate elimination’.