I personally wouldn't use poison, but If you think it's a mink and you don't have dogs or cats around, here is a sure fire way to catch pretty much any critter. I used to trap many years ago and my best results always came from this method. First you'll need a steel leg trap (bigger then a muskrat trap), dig a hole angled into the earth, not straight, make it about a foot deep. Place the bait at the back end, could be road kill, maybe a dead crow or what ever you can find. Place the steel trap at the entrance just covered lightly with leaves. mask the front of the hole with small sticks so the critter has to step in front of the hole to move the small sticks out of the way to enter the hole. Mink and weasels are very smart so you have to take into consideration not leaving anything out of place or they will avoid the trap. Don't be surprised if you have a coon, fox or opossum, all critters you don't want around your cop anyway. Then you can use the .22 to dispose of the critter, when that time comes. Always check your trap so the critter is not left suffering for to long. Good luck!!!
He has already dug tunnels everywhere around and under my coop floor...can I use one of his existing tunnels and put the trap in that way? And will fresh deer meat work for bait?
It's definitely a weasel or a pine marten, the tunnel is small and I have seen them around here the past few years, the run back and forth along the lake ice in the winter. In any case he's very smart and very sneaky!!