Pacific Gopher Snake (Pituophis catenifer catenifer)
Forgive the very small image size… it's a small snake, and the 80-400 is by no means a macro lense.
We weren't certain at the time that this wasn't a rattlesnake, because although probably a full-grown adult in fact, that happens to be about the same size as a very young rattlesnake.
The two characteristics we didn't realise at the time, that each clearly mark it as not a rattlesnake, are (apparently):
a) The round pupils. Rattlesnakes have the stereotypical narrow vertical slit pupils, a la cat's eyes. Gopher snakes have much rounder if not fully round pupils (as this one does).
b) Juvenile rattlesnakes don't have a full rattle, but they do still have a 'scale' or 'button' at the end of their tail, which is noticeably stubby. Gopher snakes have long tappering tails, to a sharp point.
It's lucky that it isn't a baby rattlesnake, as some completely oblivious guy with headphones on stepped fully on it, and then *stopped* and stood on it for a few moments, before he finally realised why we were waving our arms wildly at him and motioning for him to stop. Sigh.
Luckily the snake appeared unharmed, though the poor thing was probably terrified. 😣