Quite often John will take Buddy down to the church and let him run around the softball field there. Since the field is surrounded by open land there are a number of groundhogs that go to the field and apparently buddy got wind of one that had just dug a hole. He loves chasing and decided to start digging to find the critter. 
It was interesting to watch how long he stayed motivated to get one. A while back he caught one in our backyard and must have really been impressed with himself because he wasn't about to give up until John grabbed him by the collar and drug him back to the car.