The Pacific Mountain Rattler, Crotalus viridis oreganus , belong to the family Viperidae, subfamily Crotalinae, and genus Crotalus . Species classification is dependent upon scale morphology and patterns . Pacific Mountain Rattlers are pit vipers.
Pit vipers are a group of venomous snakes that have depressions in the front of their eyes.
These pits serve as heat sensing organs that aid in the detection of warm-blooded prey. These pits regulate the amount of venom injected into their prey to kill the animal. Their two parted tongue enables the rattlesnake to smell. The delicate tip of the tongue carries particles to Jacobson's organs. The color of the Pacific Mountain Rattler, Crotalus viridis oreganus , can be a dark gray, olive brown, or black.