I spoke to a guy recently who was considering running chickens in his woodland and it had been suggested to him that he should set up a number of poacher traps around his runs in order to scare off foxes and badgers (apparently badgers will tunnel under fences to get at slugs on feeders which allows foxes to gain access).
Poacher traps, as far as I'm aware, are trip wires attached to some sort of trigger mechanism that, once tripped, drop a metal weight with a 'cap' on the bottom creating a loud bang.