A Western Pigmy Rattlesnake, Sistrurus miliarius, a venomous North American pit viper, reacts to a perceived threat with head movements and finally moves backwards

animal small animal reptile snake pit viper western pigmy rattlesnake venomous caution dangerous warning sistrurus miliarius wild wildlife closeup predator serpent coldblooded reptilia nature beautiful defensive behavior united states north america daytime outdoors wary alert vertabrate fauna pattern close up low angle view