Mine are in a chicken tractor. I have not had any issues with snakes (yet) since ethey have been in there. The only time I had a snake get into a coop
was one that was rather large, and non moveable. It didn't eat the chickens, but it would sometimes eat an egg. Even though I am not a huge fan of snakes, it was nice tht it kept the mice at bay. HOwever, with the coop I have now, I have not had an issue with mice or snakes. It has a 2 by 4 wire in the run(portable run) and in the floor of the coop (portable) so that droppngs will fall through. Also, on the floor I have a plastic mat that I place over the wire, so their feet are more comfortable, The mat is porous so things can fall through. Howver, it is closer woven than the 2 by 4 wire. A snake would not go through it.