Man, I feel your pain!! I've got groundhogs all over my Ohio farms. Usually use a .22LR and that works pretty good (and is also a lot of fun) but you have to catch them out in the open so it's a "hit or miss" solution (hee hee).
I'm definitely going to try the dirty cat litter option! My daughter has a cat so I'll have her save a few bags of Ninny's poo and give that a try ... I'm sure my daughter will be thrilled to keep a few stinky bags of dirty litter in her garage until I can pick it up!
They used to sell these vibrational doodads you stick in the ground. Might be your first option.
I'm not a groundhog psychologist so I don't know why they would burrow under buildings. Are they dirt floor buildings? Looking for food probably. Used to have them in pa but didn't cause any issues. Depends on where you live but you could do sacrificial plants of food they eat away from the buildings, would be the easiest/cheapest way to do it. Maybe carrots would do it just gotta make sure they grow.
Nope. Sacrificial foods is not a solution. They actually eat a pretty healthy diet ... usually clover, grain, berries, etc., but I've never noticed grubs as being a major diet feature.
The problem isn't that the groundhogs damage so much by eating, (although they will play hell with a vegetable garden), it's their burrowing that is the problem. Those damn things will dig a burrow nearly anywhere ... under stumps, INSIDE of dirt floor sheds, under sheds, under concrete floors, or out in open fields (suffered lots of farm implement damage from a wheel suddenly dropping into a burrow I didn't see!!). But, for some unknown reason they do have a affinity for burrowing in and around buildings.
Charles,
Today, as I was working on my lawnmower, the wonder of one's subconscious was made apparent when the word "Cyanogas" popped into my head.
Your description (below) matches my recollection of the "powder" and when I clicked on the link, the article mentioned a liquid form that my dad mentioned when I asked him about the "groundhog killer" we had used.
After I looked at the Wikipedia article I did a Google search for cyanogas and found several references. Scott
Nice research, Scott!! Cool old advertisement!
Also, bare in mind there's almost always two burrow holes, a primary and a secondary, so both have to be plugged if you are going to use a suffocation method. And be careful with gas/fire methods that back-blow from the secondary entrance doesn't set your shop on fire!