"Don't Tread on Me!" Crotalus atrox, the "western diamondback rattlesnake", is a venomous rattlesnake species found in the United States and Mexico. This juvenile is well camouflaged against the gravel and asphalt of a roadway, and might be a good reason to use a flashlight when traveling at night, as they seem to enjoy the residual heat of pavement on cooler evenings. This particular rattlesnake was allowed to safely retreat after posing for a few photos.