An electric fence is a psychological deterrent that is designed to keep livestock in or nuisance animals (predators) out.
The psychological element is achieved because… well an electric fence hurts. I would stress at this point a electric fence using modern equipment will hurt but not harm any animals or humans who might be unfortunate enough to come in contact.
Whilst to some this may appear cruel it is significantly less cruel than the use of barbed wire where the barbs were designed to perice the skin and inflict pain on the animals .
Electric fences can be either temporary or permanent and through the use of modern light weight plastics can be very easily moved around a large area as required. Additionally electric fences are extremely adaptable in the application and can be used from keeping livestock (horse, sheep, cattle) contained in kent to keeping monkeys out of second-storey windows in malysia.