After looking for a while, I started to wonder. Then I took a separate trail and almost immediately found what we were looking for. His first ever live rattle snake was a Great Basin Rattle Snake. The rattle snake was very calm. It never rattled and only held this defensive posture for a few seconds after I kept blocking it's escape.
When the rattle snake was on the ground, it was hard to see it, but it had 2 distinct prey lumps. They were easier to see with the snake suspended over a stick.
Kangaroo rats were most likely what the snake had eaten. We saw quite a few of these guys hopping around. Kangaroo rats never need to drink water their entire lives. They have special kidneys that allow them to survive on only the moisture from things that they eat. I have no idea what purpose the super-long tail serves. Really, the tail encumbers the rat (mouse) and makes them easy to catch.