So, I researched for probably a year before building my coop/run, and I have always thought it was as secure as Ft. Knox. The floor has hardware cloth, all of the walls are hardware cloth, all of the windows and vents are hardware cloth, all of the trim is caulked, etc. Never had any issues until my neighborhood recently started clearing a nearby field for new construction, and now the field mice are everywhere. Started seeing mouse poop in my run, so I repointed my night camera to that area, and we're seeing several mice running around in the run every night. I've gone back through the whole coop/run looking for anywhere that they could be getting in, but can't find anything. There is no sign of digging/tunneling; there is no sign of wood being chewed. They are avoiding the snaptraps that I've set (I put them in the run after our girls have gone to the coop for the night, and remove the traps before the girls wake up). They've avoided all of the snaptraps that I have set around the the outside of the coop/run. The only way that these things can be getting in is by going through the 1/2" x 1/2" hardware cloth, which just doesn't seem possible. Anyone else experienced this? I don't know what to try next. To change to 1/4" x 1/4" hardware cloth would be a major task...nearly impossible.