John Cancalosi / Western diamondback rattlesnake (Crotalus atrox). Arizona, USA

John Cancalosi / Black-tailed Rattlesnake (Crotalus molossus) "Smelling" or "tasting" the air with its tongue. Chiricahua Mountains, Arizona, USA

John Cancalosi / Black-tailed Rattlesnake (Crotalus molossus) "Smelling" or "tasting" air with tongue, Arizona, USA

John Cancalosi / Close up of rattle of Timber rattlesnake {Crotalus horridus} USA