A gopher snake, Pituophis catenifer.

A harmless gopher snake will sometimes mimic a rattlesnake by vibrating its pointed tail and shaping its head into a triangle. However, gopher snakes never have a rattle on their tails, are usually thinner throughout the body, have a glossy body, have round pupils in their eyes, and their heads are only slightly larger than their necks.; Credit: Tyler Young
Credit: Tyler Young