Cats leave home for a variety of reasons, but the two most common are curiosity or fear. An outdoor cat may enjoy exploring a new neighborhood, or an indoor cat may slip out the door. Cats also clash with each other, with dominant cats chasing away submissive ones.
While feral cats form colonies, each cat has his own clearly marked area that is further divided into territory and home range. A cat is willing to defend his territory, which is usually smaller and located within the home range; however, a cat's home range is the area in which the cat hunts and feels comfortable interacting with other cats. Male and female cats often have overlapping home ranges. A cat may feel hostile or aggressive to an unwanted cat entering his home range and chase the intruder out; feral cats sometimes harass domestic cats in this manner.
An indoor cat is less likely to abandon his home because of his territorial urges; however, if he inadvertently escapes, he usually takes shelter as quickly as possible and may become disoriented and unable to return home. An outdoor cat may vanish because he has fallen ill or has been captured by a well-meaning person. He may also have fallen prey to another animal or climbed into a container and been accidentally transported.