Like two post before snakes can live in cold weather. You have to remember in most deserts it gets very cold at night. Do you have any small spaces under you coop? Cause if you do they would love it. We have had situations where there have been snakes under the coop. And when you let them out i would look for makings on the ground around the coop. For any prints of feet or snake lines in the dirt. Hope you get whatever it is.