Cats in the wild use marking as a way to communicate with one another. The actual process of marking can take a few different forms. Cats most commonly spray urine over areas to ‘mark’ them. Cat urine has a fatty component to it which helps the urine ‘stick’ to objects. This is also the component that makes cat spray have its distinctive and potent odor. Marking with feces can also occur, although this is seen less frequently.
Cats also have scent glands on their chin, on the sides of their forehead, around their eyes, below their ears, around their anus, at the base of their tail, and between their toes. Scents can be released from all of these areas as well. A good example of this is when cats scratch. This action not only leaves their scent behind but are also creates a visual marker for other cats to see and be aware of.
Cats of both sexes (although males tend to mark more than females) mark as a sign to other cats that a certain territory is theirs and/or that they are the dominant cat in the area. Cats in heat and males responding to a cat in heat will do a lot of marking as they go on their quest to find a mate.
It is fairly simple to break a cat of bad scratching habits and urine or fecal marking behavior (both however do require time and patience). In most cases spaying or neutering the cat will be enough to stop him/her from marking. If that doesn’t fix the situation try to reduce your cat’s need to mark by making sure your cat feels his/her territory is sound and that his/her dominant position (or position in the hierarchy) is safe. This means you will need to figure out why he/she is marking (is there a new cat in the home, can he see another cat from a window, did you just get a new pet, are you favoring another cat who isn’t the ‘dominant’ one) and then try to combat the problem from that route.
If your cat has marked quite a bit in the past you will need to remove all signs of the mark using a special odor controlling solution. Although you may feel you have cleaned the area thoroughly and that it smells fine, cats have a keen sense of smell and will most likely still designate the area as being marked unless you have used an odor neutralizing solution designed for cat urine and spray. Until the area is truly clean your cat will continue to go back to it and re-mark. You can purchase such products at your local pet store. You can also help your cat stay away from the spot by spraying it with a vet-approved cat repellant which can also be found at your local pet store.
Note: Cats can mark due to illness. So before you start trying to correct marking from a behavioral standpoint take your cat to the vet to rule out any sort of health problem that could be the culprit.