Are Rattlesnakes Only Found in North America?

My father-in-law posed this interesting question to me over the holidays last year: Are rattlesnakes found only in North America?

The answer: No, although they are found only in the Americas (North and South).

There are 27 species of rattlesnake, split into two genera. (The genus Sistrurus consists of 9 speices found exclusively in Canada, the United States, and Mexico. The other 18 species are of the genus Crotalus, found from southern Canada to northern Argentina.)

Above: The Southern Pacific Rattlesnake I encountered in Dana Point two years ago; my first rattlesnake encounter! Very exciting!

That they are found only in the Americas suggests that rattlesnakes branched off of their more general pit viper ancestors in fairly "recent" times, geologically speaking. (Recent enough that North and South America had separated from the other continents; the evidence points toward that the ancestor probably originated in the region of the Sierra Madre, Mexico).

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If you have a burning question about nature or natural history, I might enjoy finding the answer for you. Feel free to email it to me.