Well, it appears that you have "handled" this particular dilemma pretty well. Around these parts, woodchucks are just like dope dealers in Washington, D.C. When one of them gets shot his cousins move into the house the very next day!!!! It is about impossible to wipe them out of this area, but I am sure there are areas that it can be done. One thing we do when they get thin is to refrain from killing them in the early spring when they first come out of their dens...if it's a big female and you kill her you probably killed the entire litter. One other thing I have read about them is that in the wild just about all of them only live three or four years because they get a form of "woodchuck hepatitis" that is extremely contagious, but thankfully only to woodchucks. When that comes around it really knocks them back.