Bike Goddess beat me to it - my guess is a marmot too, but they have tails. Maybe he lost his?

Yesterday I came upon a 4' rattlesnake stretched across my path! Stopped me dead on the trail...er...fireroad. I threw a rock at him and he turned around and slithered off. When his tail end left the road I passed, but he curled up and rattled at me!

You did great on that ride! Keep it up!