One reason is that they dig under the foundations of my farm buildings. When my granddad was farming I cannot tell you how many cows were put down because of broken legs from cows stepping or falling into a groundhog hole. Just last year I had 30 feet of bank of a creek that runs through our property wash out and it cost the local county over $30k to repair the damage and replace a drain tile becuase groundhog holes had weakend the bank.