Outdoor cat suddenly stopped using litter box

My guess is your cat is acting on feline instinct to go to the bathroom outside. Admittedly, my experience with cats is limited to the one I got at age nine months last fall (now 15 months), and I don't know his history, since I got him at the shelter. But I notice him changing and developing new habits as he gets older, just like a human child developing over the months and years.

He always uses the litter box, like you describe, but also used flowerbeds when I first had him outside on a leash. However, I live in an apartment building and was told that letting a cat defecate in the flower beds is not okay. Next time he wanted to do it, I didn't let him but quickly took him inside. Now he knows not to use the flower gardens but to use the litter box.

Did he learn from other cats to use the flower beds? I don't know. Considering how easy it was to wean him from the habit, one would think it was just an instinct he was trying to act on, but when it didn't work out he gave up on it. All of this is just guess work on my part.

However, he figured out how to climb up and down trees. I kept him on the leash and only let him go as far as I could reach until he knew how to get down on his own. He didn't learn from his mother, just from his own instinct. He is teaching himself to hunt as best he can when on a leash; he stalks squirrels, he watches the birds. When I showed him cat videos of birds and squirrels on my computer screen, at first he kept looking behind the monitor to see where they went. But now he knows that it's like watching out a window--he can only see what's in the little square of the monitor.

All of this tells me that young cats act on instinct and learn by experience with their environment what works, what is comfortable, etc. If you can't smell or see anything amiss, my guess is that nothing is amiss. But, as stated, this is all guess work on my part.

how likely is it that a young cat, from one day to the next, learns to go to the toilet outside and starts preferring it to the point she doesn't use the litter box?

What you describe suggests it could have happened over a number of days, even if you didn't notice right away. But you can see from my cat that they do try different things. If you are worried about your cat's health, by all means talk to your vet. Even in lockdown, I have been able to communicate with the vet's office and get routine prescription and other advice.

When I still lived with my parents I got them a cat which grew up on a farm (it was about 6 months old). He quickly learned to use the litter box and only peed once on the carpet in the living room. When he was allowed to go outside he rarely used it, only when he was inside for a longer time period and then mostly for peeing. Some time after that he completely stopped using the litter box inside and even woke us at night if he had to go to the toilet, so we could let him outside. He now is about 8 years old and his health is fine. He did not use the litter box for the last 6 years.

His litter box is now in my appartement for my little kitty I got 6 weeks ago. This one also grew up on a farm but knew the litter box from the beginning and learned it from his mother. He is allowed to go outside for about 2 weeks now and still comes back inside if he needs to go to the toilet ;-) But I guess he will stop using it too after some time.

Its the most natural thing and if the cat is allowed to roam freely outside it will also pee and poop outside if it finds a place to bury it :-)

Cats prefer to keep their living space clean. This means doing the... ahem "business" somewhere far away. If your cat is free roaming, she is most likely following her instincts and going to alternative locations. Places with loose ground, with sand, whatever works.

Even if she has never seen other cats do it, her instincts will tell her how to do it. It is how cats learn to use litterbox, they associate it as the place to defecate and their instincts tell them to bury the results. However, having ability to freeroam means that your cat now has somewhere further she does her business at.

If your cat shows no signs of distress of feeling sick, you should assume that scenario 1 is in the play: She wants to keep her home clean and for that reason, she will head out somewhere else to do her business. Out of sight, out of mind after all.

As for the possibility of your cat relieving herself outside: she might have picked that up from other cats in the neighborhood, who might also have taught her the spots to use. By instinct, cats usually do that sort of business at the “edge” of their territory, as far as possible away from their living space. If your cat’s territory extends beyond your garden, it is quite likely that your neighbors are getting gifts from her.

It is quite normal for outdoor cats to stop using the litterbox in favor of a place outside: my old cat used the litterbox when she was young, but hardly ever as she grew up. I have also heard reports of people who eventually got rid of the litterbox for their cat.