Territoriality is a behavioral drive causing animals to set up distinct territories defended against other members of the same species (conspecifics) for the purpose of establishing a breeding site, home range, or feeding area. It is an important factor in the spacing out of animal populations. Territoriality is shown by animals of all kinds: birds, mammals, fishes, and insects, and may involve physical displays, noise-making, aggression, or the scent-marking of boundaries. A territory may be held by individuals, pairs, or even family groups.