Over 50 years ago, Noble (1939) defined a ter ritory as “any defended area.” This deceptively simple definition has stood the test of time, because it incorporates three of the key elements in any territorial system. First, defense is impor tant: in some fashion, the behavior of a territory owner discourages other individuals from using an area. Second, space is important. In contrast to dominance relationships, which do not vary as a function of location, the hallmark of a ter ritorial species is that the type and outcome of social interactions are location-dependent. Fi nally, Noble’s definition implies that animals need not defend every area used on a regular basis; that is, Noble’s definition presages the later distinction between a home range, or the area used for an individual’s daily activity, and a territory, the portion of a home range that is defended against other animals.