The spatio-temporal management of stocking density will be possible once virtual fencing (VF) becomes a commercial reality.  VF uses sensory cues (currently audio and electrical stimulation) to change an instrumented animal's forward direction of movement.  Free-ranging cattle instrumented with VF electronics wear hardware that identifies where on the landscape the animal is located, most frequently using the Global Positioning System (GPS).   In addition, Geographic Information System (GIS) hardware and software, also born by the instrumented animal, can be programmed to identify the location of a polygon (paddock) on the landscape. When an instrumented animal attempts to penetrate the polygon's perimeter audio and or electrical stimulation cues are administered autonomously to the animal's head or neck region to change its forward direction of movement. By ramping the cues from least to most irritating each animal customizes the lowest level of irritation it requires to change its behavior.  To date research has yet to determine what percent of a herd needs to be instrumented for acceptable control in all landscapes, seasons and with all breeds of animals or how best to generate and store power to keep the animal born electronics functioning for extended periods of time without human intervention.  Though conventional fencing will never be completely replaced, VF has the potential for holding as well as moving animals over a landscape in real-time.