Big Chicken, if you are having trouble in and around the pens, and can't catch up with it, maybe try a wire? Works even when you sleep, and if you can find its run. . . . jobs a good un.
However, when shooting or trapping foxes at this time of year, if its a milky vixen, we always track down and deal with the cubs, not very fair otherwise. But funnily enough a job most shooters just conveniently ignore. . . .