Water pistol pfr. Better still, one of those large powerful squoosher things children play with. Very effective (voice of experience with Psycho-Cat and his evil mate Ronnie, who are terrorising the neighbourhood round our way)

Foxes can be heard screaming in a blood-curdling fashion during the mating season. The females particularly sound like murder is being committed. Good job we humans don't do that - could be a bit embarrassing!