The gopher snake will vibrate its tail when alarmed, as do many snakes, but the gophers tail is banded in yellow and black. This banding makes the tail look like a rattle when it vibrates. Nervous gopher snakes will flatten the head in a way that makes them look like a rattlesnakes head. The dark stripe from the eye to the back of the jaw helps in the deception. The final, and possibly most effective, trait is the hiss.
Gopher snakes have a piece of cartilage in the mouth that vibrates when the snake hisses.
This vibration adds to the sound of the hiss in a way that makes it sound like a rattlesnakes rattle.