Bringing a new cat into a home with other felines is always tricky. In the presence of an unfamiliar cat, you may find your pet's innate territorial side coming out -- in full force. She may even start urine marking your home to show the newbie who is in charge.
One way to remedy your cat's territorial urine spraying habit is by getting her spayed, pronto. Although some cats do indeed spray even after getting fixed, the surgery usually either eliminates -- or at least greatly minimizes -- the pesky behavior. If you spay your territorial fluff ball, remember that it may take a couple of weeks or months for her hormones to fully calm down, though her spraying eventually will cease -- phew.
Curb your cat's territorial spraying by keeping previously sprayed areas immaculate. If your cat has marked a specific place in your home before, say the den sofa, be sure to meticulously clean the area so she doesn't have any "scent reminders." Avoid cleansers that have particularly aggressive fragrances, however. In some cases, especially harsh smells can encourage cats to spray in an even more overzealous manner -- no thank you. Try an enzyme cleaner to completely remove the urine stench.
Cutting Off Access
If you notice that your jealous cat has a preference for where she likes to spray, try to make it so that your pet just can't access the spot anymore. If it's the basement, temporarily lock the basement door, at least until the chaos of the new cat subsides. In cases where cutting off access just isn't possible, try to alter your cat's association with the place. Perhaps give your cat a few yummy treats there so she mentally links it with food instead of the urge to mark.
When it comes to urine marking, there are no guarantees that a cat will stop the habit, unfortunately. If you notice, however, that your precious pet's spraying is particularly persistent, consider the possibility that it may not be related to the new cat at all. In some instances, spraying is actually a symptom of various medical conditions, including bladder stones, urinary tract problems and incontinence. Incontinence is especially problematic in senior cats. Don't simply blame your cat's spraying on jealousy -- get her behavior checked out with the veterinarian as soon as possible.
To prevent territorial issues between an older cat and a new cat from beginning in the first place, take the initial introduction process slowly. Before introducing your new addition to your resident kitty, isolate her in a private sanctuary for a few days. Give her time to get used to her environment, from the smells to the sounds. When you feel like she's ready, allow her to interact with your previous cat -- with close monitoring, of course. If both parties behave calmly and without aggression, reward them both with tasty treats.