Definitions of this term vary depending on whether it is being used by geographers, specialists in animal behaviour or anthropologists. In the context of prehistory, it is often used in the narrow sense of referring to the area of space that a group of hunter-gatherers would travel across annually in order to provide for its dietary and material needs. Each human group had its own system for the perception of the space that it travelled through: as well as perfect knowledge of the available resources, these prehistoric societies must have had some symbolic perception of the territory they inhabited and travelled across.