Animals and humans are 'territorial' - they mark a piece of ground and defend it against intruders. Fish, worms, gazelles, and lizards stake out particular areas and put up fierce resistance when intruders encroach on their area.
Many species use odorous secretions to mark the boundaries of their territory.
For example the wolf marks its domain by urinating around the perimeter. The dog barking at you from behind his master's fence acts for a motive indistinguishable from that of his master when the fence was built'. In a library you protect your space with a book, coat, or note-book. You 'save a place' in the theatre or at the beach reserving a spot that is 'mine' or 'ours'. Juvenile gangs fight to protect their turf.