My cat had kittens recently. They’re now over 2 months old, and I have had to clean up behind them exactly two times, ever.
I have never spent any time training them to use the litter box or newspapers or anything like that, but they always go to the box to use the bathroom.
So, do cats instinctively poop on dirt if it’s available, or is my cat Super-Cat-Mom, who trained her kittens to use the box so that I wouldn’t have to?
I guess it’s worth noting that she didn’t take to the box naturally, and I did have to clean up after her quite a few times.
What’s the deal? The third possibility is that they have a secret place behind my couch where they’re doing their business, and I just haven’t found it yet. 
But nothing smells funny, so I guess that’s not it.
Cats have an instinct to dig and bury their doings, which is reinforced by their mothers. Sometimes if a kitten is taken from its mother much too early, you have to teach it to dig, but they usually catch on quickly. Even in the wild, they’ll go for sand or loose dirt where they can dig, which is why children’s sandboxes and the neighbor’s garden are so appealing to them.
Mama cat teachs her babies to use the litter box. It’s instinct in cats.
Isn’t that neat?
And that is one reason why cats make such great pets.
I have two cats that I got as 6-week old kittens. They were outdoor farm cats. AFAIK, they never even HAD a litterbox to use before I got them.
The advice I got on how to train them, which I followed, was: put them into the litter box at first so they can tell they can dig in it. Shut them in the same room with their litterbox for the first night or two, so they know where it is.
That was it. In more than 5 years, they’ve never “missed”. If I could only train them to run onto the tile floor when they barf up the odd hairball…