Try large and small rock with steel chicken wire under it. For larger rodents that will eventually show up. I have wood chuck digging under mine and use chicken wire to slow them down. I never used the rock but I think it will help with them digging next the the building.
Never tried the below but hear plaster of Paris mixes work well and not to harmful to pets.
Bait:
Shallow pans or bowls baited with corn meal, brown sugar, and plaster of Paris. The mixture is most effective when it consists of 2/3 of corn meal and a sixth each of brown sugar and plaster of Paris. First, mix the corn meal and plaster of Paris to ensure that plaster of Paris is spread evenly throughout the mixture. Soft brown sugar makes mixing easier.
Or
I Just found a recipe for home-made pet friendly Rat and Mouse killer on a website from Tennessee as follows :
1 cup of flour
1 cup of sugar
1 cup of baking soda ( Bicarbonate of soda)
Mix together and place in small bowls where you notice rodent traffic.
Says it's safe around household pets.
(The bicarb will react with stomach acid and produce carbon dioxide gas, obviously in excess to create the swelling. Apparently, most of these vermin and creatures cannot pass wind, hence the internal combustion. )
