Spraying is a behavior in cats, mainly males, which many owners confuse with urinating outside the litter box. The difference between the two is that a cat will urinate on a flat horizontal surface. Spraying is most often done on a vertical surface. Female cats will spray on horizontal surfaces, but it is rare.
The primary reason a cat sprays is because felines are very territorial animals and like to mark their turf by spraying urine to let other cats know who owns that little piece of the world. If you notice things being marked near windows or screen doors where your cat can see outside it’s a pretty good chance there is a cat hanging around your house or passing by frequently.
Many times a cat will spray because of psychological problems such as anxiety, stress or a feeling of being threatened by something or someone. If personal items are being sprayed it is usually a sign that your cat has some issues with the person. The addition of a new cat or even having too many cats for the size of your house can cause spraying problems.
If the cat is put into a stressful situation like someone new moving in (a new baby) or being introduced into a new living environment they might feel the need to spray.
By taking time to examine the events going on in your cat’s life, you may be able to eliminate this behavior. There are products sold at pet stores that contain odors only your cat can smell. These are designed to comfort your cat. Another thing that often eliminates spraying behavior is to have your cat neutered. In most cases, this is the most effective method as it alleviates the territorial instinct in your cat. This is yet one more argument for neutering.