A herd of cows on Steart Marshes in Somerset have been fitted with GPS collars which act as a virtual fence.
The collars play a tune to redirect the cattle when they come close to a boundary, and then give them a gentle shock if they do not divert.
They are used to keep the cows safe from hazards such as rising tides and ravines. The collars also direct the animals away from endangered grasses and protected species.
Video journalist: Will Richards
