All kinds of predators

[ukrkoz]

2 - 3 inches. Everywhere under the coop. Coop is on 4x4-s, raised and mesh along the bottom.

 

[carlf]

That's moles, chipmunks or gophers.

http://wdfw.wa.gov/living/gophers.html

 

[Rock Home Isle]

Get a block of dry ice and break it up, then stuff tge chunks into the tunnels. The dry ice will sublime, and tge carbon dioxide is denser than air. It will flow down into the depths of tge tunnels and stay there. Anything using those tunnels will be quietly asphyxiated.