If the snake has a speckling of red on its side, then it is a Coast garter snake (Thamnophis elegans terrestis). The Coast snakes eat almost any small thing that moves, including insects, snails ...

Brian J. Halstead, Glenn D. Wylie, Michael L. Casazza, Habitat Suitability and Conservation of the Giant Gartersnake (Thamnophis gigas) in the Sacramento Valley of California, Copeia, Vol. 2010, No. 4 ...