Rattlesnake (Crotalus), Golden Spike National Historic Site, 2016.

The genus Crotalus includes venomous pit vipers found only in the Americas. You probably know them as rattlesnakes. Crotalus stems from the Greek word 'krotalon' meaning rattle, referring to the well-known and conspicuous rattle on the end of the snake's tail. No Crotalus species is considered aggressive and will actually retreat quickly when threatened. However, do not corner a rattlesnake or it will readily defend itself. All rattlesnakes are venomous, some very highly-venomous.