I caught mine in the spring, just out of burmination, so they probably were in contact with a damp environment (in holes around the pool and under the solar heater) for quite a while. That may have something to do with it. Snakes have a petty tough life on the outside. The snakes that were in my sunroom did not show any signs of it, but they were probably in a dryer environment (under the floor) all winter. Just a guess on my part.
BTW: That is a gravid female if that helps anyone with sexing.