Not long before I spotted this snake, I had passed a "snake track" (also perpendicular to the trail), which was unusual in that it was nearly a straight line. Not the S curve I expected. The 3rd photo shows this Gopher Snake when I spotted him farther down the trail, moving slowly, and noticed his method of propulsion was to stretch his head forward and then compress sections of his body, accordion-like. Once he reached the slope he began using loops of his body for leverage in S curves as you would expect. I photographed the track this time for personal reference.