Urine Spraying
When your cat rubs against your leg with his face, or scratches his scratching post, he is also depositing his scent from the glands in his cheeks and paws. Another equally normal but less pleasant marking behavior is urine spraying--the deposition of small amounts of urine around a given area. Spraying announces a cat's presence, establishes or maintains territorial boundaries, and advertises sexual availability.
Cats usually spray on vertical surfaces, like the backs of chairs, or walls. They don't squat to spray (as they do to urinate), but the tail lifts and quivers, and small puddles of urine are left in several consistent locations. Cats that spray are usually unneutered males and, to a lesser extent, unspayed females, but 10% of neutered males and 5% of neutered females also spray. In households with more than seven cats, the likelihood of spraying is high.
Cats may spray when they perceive a threat to their territory, such as when a new cat enters the home, or when outside cats are nearby. New furniture and carpet smells can prompt spraying as well. Cats may also spray out of frustration resulting from factors—like restrictive diets, or insufficient playtime—often wrongly perceived by humans as revenge.