We don't have groundhogs around here, but my dog hunts squirrels instead. The first time he latched onto one, it turned around and bit onto his lip. He tried shaking it off but the squirrel hung on. He got a little bloody. Since then, my dog has learned to do the "fast crunch".
Reminds me of one morning walking our Soft Coated Wheaten Terrier and Giant Schnauzer. The SCWT spotted a ground hog and true to her terrier breeding went after it. Some how the groundhog got his upper front teeth caught in the metal loop on her collar. About that time the GS decided to join in and got the GH by the tail. So there they were the SCWT trying to back away, the GH hooked on the collar and the GS pulling his tail in the opposite diretion. Eventualy they got untangled and the SCWT finished the job.
we had a pair of mutts one was a doberman/blue tick mix, the other a long leg beagle lasaopso mix. Rex the dobbie mix could catch/corner them then the beagle mix would catch up & GRAB the chuck in the rear. rex then would grab them from the back cruch crunch and dead....
this was 20 years ago now... the were good hunters..