X2. Electric poultry netting around your coop or run a hot wire or two around it. Consider putting an apron around your run to prevent digging under. Fortifying your coop and run is a lot easier and much more long term then trying to catch this predator, and the next one and the next one and so on, in the act. Especially fox, very intelligent and can be hard to catch. You can set traps, they may go in or they may not and may go after your birds instead. We've tried that route. I've had much better sucess at preventing dead birds in the first place with a stong coop/run. A good dog is a big plus too, as long as it does not become a chicken predator itself!
I doubt that they 'see' it, but the idea is once shocked forever educated.
