Three to four inches deep is the correct depth and the correct amount of cat litter to use in a litter tray according to a well know cat behaviourist. I’d more or less agree with her. However, I tend to fill the tray to around 1.5 to 2 inches, a little less than the behaviourist recommends but I always use wood based litter. My preference tallies with the recommendation of another cat expert, Arden Moore, who says cat owners should get out a ruler and measure the litter to a depth of 1.5 to 2 inches. This, she says, should meet the needs of most cats.
Too much cat litter in the tray probably won’t upset your cat but it will probably cause more waste. The argument is that more cat litter gets thrown out of the tray and more litter than normal is tracked out with the cat if there is too much litter.
Also it makes it harder to keep the tray clean and filtered. Personally I am not sure that these are great arguments but they may be correct. It could be argued that cat owners who fill the litter tray too much are more likely to clean it less often. Perhaps some people simply pour the whole bag into the tray and forget about it for a few days or longer.
Not enough litter would be a greater problem I’d have thought. The natural substrate on which a cat to goes to the toilet is earth. This has the feeling of being around 3-4 inches deep which supports the suggestion at the beginning of this article.
If the layer of litter is very thin it may cause litter box aversion. Also the litter will be less able to absorb urine and faeces and so create an odour problem. This will probably be uninviting to your cat. Also cats like to dig into the ground before defecating and urinating. Then they often cover it up afterwards. These actions require the litter to be at a reasonable depth.
The type of litter (clay or wood for instance) may also be factor. I think wood based litter can be more thinly spread that clay based and be as effective as it is a more efficient odour absorber and is not clumping.
There is one last factor. The cat has a say in this. Cats are individuals and cat owners should be observant of their habits and preferences. I would expect cats to like litter at the depth recommended above but perhaps a little experimentation may be useful. It may help get rid of an inappropriate elimination problem.
What do you do?