How to Determine Which Cat is Peeing Outside The Litterbox

When a cat owner discovers that their precious kitty has peed on the carpet or rug, the first reaction is usually to jump to conclusions about exactly who the culprit is.

In a home with just one cat, it’s obvious who did it.

But what about a home with multiple cats? Or a dog? Don’t assume you know who it is, urges the book Cat Scene Investigator. You might be surprised so gather some evidence rather than rely on intuition. Here are some ways to figure out just who is going where he shouldn’t.

Catch a Cat in the Act

This method leaves no doubt as to which of the cats is the perpetrator, but it’s not very practical. For those that have a job outside the home and kids to take care of, watching a cat go about their lazy day for hours on end is probably not a reasonable solution, but you might just get lucky. If not, try some of these other tried and true methods.

Video Surveillance

Cats tend to return to the scene of a previous pee incident over and over. This makes video surveillance a relatively easy and surprisingly inexpensive (several models in the $50-$60 range) way to identify the offending feline. These cameras can then be paired with your smartphone so you can review the footage, making this option the most accurate and reliable method. Cat Scene Investigator urges us to not stop surveillance once one cat has revealed himself as the offender. There might be multiple wayward pee-ers in your midst.


Cat behaviorist Pam Johnson-Bennett, author of the book Catwise, suggests using Fluorescein, a fluorescent dye that  in ultraviolet light. Also used by ophthalmologists to detect eye injuries, this solution requires your vet to administer fluorescein capsules to one cat at a time for a multi-day cycle. After your cat has ingested the harmless organic agent and has had some time around the house, use a UV light to locate pee spots. Start with the litterbox. If the box lights up in a light-green color, then the cat in question has been urinating in the litterbox. If you see this color when lighting up the carpet, a rug, or furniture, then you’ve found an improper eliminator.


For those who are looking for a cheaper solution, try confining one of the cats to a small room equipped with a litterbox.  Keep the cat in the room until he pees (keeping in mind this could take several hours) and once he does, determine if he made it to the litterbox or not. If he didn’t, then you probably have at least one of the culprits, but you’ll have to isolate each cat in turn in order to eliminate all non-offenders. This method is not as accurate as removing a cat from his normal environment changes the overall dynamic and could impact behavior as well.

Visit the Vet

Once you’ve determined the wrongdoer, get that kitty to the vet. The problem may not be behavioral and instead might be something that requires treatment, such as a urinary tract infection or idiopathic cystitis.

If you have a multi-cat, multi-pet home, determining which of your cats is peeing outside the litterbox could be a daunting task. However, the use of these solutions, used separately or in tandem, can help you to quickly pin down the perpetrator and take timely, corrective action.

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