Our cat Buster has been pooping outside her litterbox but pees in her litterbox. She has never behaved like this so we were concerned. We did a search on the internet and found that we weren't alone. We found the following article helpful for us and hope it will be for you too.
Cats - Pooping Outside the Litterbox
Expert: Jessica - 6/7/2004
Question: I have had my cat for 2 years, she is 2. When I would go out of town she would poop outside her litterbox. I assumed that it was because she was mad at me. But in the past 2 weeks she has been doing that everyday, when I'm at work and once while I was home. I have never had a problem with her going to the bathroom in her box.
Answer: Defecating outside the box tends to be related to a physical ailment more often than urinating outside the box, so I'd start with a visit to the vet. Gas, constipation, impacted anal sacs, inflammatory bowel disease, and gastrointestinal parasites and infections can cause discomfort upon defecation, and this can cause the cat not to use his litter box, which she grows to associate with the pain.
Once those are ruled out, you should look to the litter box. A great majority of cats prefer to use one box for pee and another for poop. Often, adding another box will solve the problem.
If the problem persists, you may be looking at anxiety-related behavior. I've heard many, many people who feel their cat is pooping on their bed or in their laundry, etc., out of spite. Truth is, it's more likely due to anxiety the cat may be feeling about whatever you feel has angered her. Scolding, bringing in a new pet, vet trips, or leaving on vacation are common triggers of inappropriate elimination. In contrast to many experts, after years of being surrounded by dozens of cats, I do believe cats have quite a sense of vengeance. However, I think you'll find that, if you reduce the anxiety surrounding whatever the situation may be, you will see an improvement.
This can be done in a couple of ways. The first and most obvious is, don't stress the cat! Try to identify what it is you do to cause her behavior, and eliminate it if you can. I'm not sure if you scold the cat or not, but if so, stop. It's not very effective and causes anxiety.
If you're not able to eliminate the cause of her anxiety, I suggest to purchase some Feliway. Feliway is a synthetic pheromone - hormones proven to induce relaxation and a feeling of safety. It's an excellent tool to use at all times, and is essential, in my opinion, for use prior to and during vet trips, vacations, and any other situation that may cause stress. It's available at pet stores and some vet offices, too.
Because you mention the behavior worsens when you leave her alone, separation anxiety comes to mind. Defecating outside the box is a number one complaint. Feliway can help in most cases. I also HIGHLY recommend getting another cat, or even a dog, to keep the kitty company. Cats who live with other cats are much healthier physically, emotionally, socially, and mentally than cats who are single pets. Adding a companion that will be with him 24 hours a day dramatically helps separation anxiety. I wouldn't suggest doing this right now, if she's having obvious anxiety problems. Adding a pet can make it worse. But once she's feeling more at ease, it may be something to consider to prevent future episodes.
In the worst cases of anxiety, a prescription anti-anxiety medication usually works. Talk to your vet about this.
Don't forget to clean the stained areas with a pet stain remover. It needs to be an enzymatic cleaner, which breaks down the fats in cat waste that cause the stains to cling to carpets and other surfaces. Nature's Miracle and Especially for Cats are enzymatic cleaners available at pet stores. I also highly recommend Greased Lightning Orange Blast, which uses orange oil to break down fats.
Unless you remove the stain, the cat is likely to return to the accident area. A cat's sense of smell is 14 times more sensitive than a human's, so even if you can't smell the stain, the cat can. That's why it's so important to use an enzymatic cleaner to remove stains, not just cover them.
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