Imagine the virtual field – but with real cows. That’s what scientists in Australia have been doing. They’ve spent three years developing a project with the wonderful name ofBovines Without Borders, intended to make sure cattle don’t stray from their fields. The system creates virtual boundaries in a field using GPS technology. As a cow approaches theboundary, the battery-powered collar it wears emits a hum. If they continue, then sound becomes a low hum. When they reach the limit, the chip-fitted collar gives the cow a mild shock. Testshave shown that the cattle learn to adapt within an hour, mostly from the sound. The collars only emit a 250 milliwatt shock, approximately the same as that from static electricity. “It’s an invisible electric fence,” explained Commonwealth, Scientific and Industrial Research Organisation spokesman Andrew Fisher. “Theboundaries are drawn by GPS and exist only as a line on a computer. There are no wires or fixed transmitters at all. It achieves the same result as a conventional fence without posts and wire.” However, it’ll be a while before Bovines Without Borders reach a farm near you. Since the current collar battery life is just a week, practical commercial versions are still severalyears away.