We only had two this year. Thankfully. I kept trying with the .22 but they were always looking up towards the house and they run and are fast. Asked a friend whose son is a farmer. Groundhogs can cost him 20K a year in lost soybeans. He sets 5 traps a day each right inside the hole entrance. When the varmint comes up it trips it and in killed at the neck. He is over 95 as of last week from those 5 holes. Probably has hit 100 since we talked last. His dad brought a trap over and within a week had gotten them both.
The farmer is probably using Conibear body traps. You can put them in a hole, blocking it, & it can get them by the neck or body as they go through. These traps are dangerous to handle & you have to make sure domestic (pets) dogs & cats don’t have access, or any other animal you don’twant to kill. There are also laws in some places that apply to these kill traps.
I wish I could use them, but the neighbors have cats that visit & while they aren’t likely to go in a hole, I don’t want to chance it.