In my younger days, groundhogs were so thick they would eat five or ten acres of a bean field that had woods nearby.  Used to carry a pistol when cultivating to help eradicate them, never thought they would almost be extinct as they are now.  When deer were introduced in our area, coyotes were introduced also, and the coyotes eradicated the groundhogs to the point that one is seldom seen.

When they were thick and did so much damage, I was bushhogging a pasture.  While backing up to mow a corner with a semi-mounted 7" bushhog mower, I saw a groundhog standing up chattering at the mower, he was mad and going to fight.  I kept backing, thinking he would run away, but he continued to fight until he went under the deck of the mower.  Moral of the story, don't fight something bigger and tougher than you!

Before carrying pistols, we used to grab the crank off the tractor (shows you how long ago that happened!) and chase down the groundhogs to kill them with the tractor crank.  Groundhogs are fast runners, and I was always slow, but the groundhog never seemed to zig-zag, just run a straight line.  If you ran at an angle to the groundhog, you could cut him off and clobber him with the crank or a 15" Crescent wrench, either would do the job.