Northern Pacific Rattlesnake - Crotalus oreganus oreganus

A study published in February 2016 used head shapes and genetic analyses to determine that there are 6 full species of western rattlesnakes found in the former Crotalus viridis complex and suggested the following names, with the three species found in California shown here at the top of the list.
If this taxonomy is accepted, the ranges and common names of western rattlesnakes found in California will remain the same, but they will be full species instead of subspecies.

Crotalus helleri - Southern Pacific Rattlesnake
Crotalus lutosus - Geat Basin Rattlesnake
Crotalus oreganus - Northern Pacific Rattlesnake

Crotalus cerberus - Arizona Black Rattlesnake
Crotalus concolor - Midget Faded Rattlesnake
Crotalus viridis - Prairie Rattlesnake

Mark A. Davis, Marlis R. Douglas, Michael L. Collyer, Michael E. Douglas. Correction:
Deconstructing a Species-Complex: Geometric Morphometric and Molecular Analyses Define
Species in the Western Rattlesnake (Crotalus viridis). PLOS ONE, 2016; 11 (2): e0149712 DOI:
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0149712

A 2002 study* split C.viridis into 7 distinct species:

Crotalus oreganus oreganus becomes Crotalus oreganus,
Crotalus oreganus helleri becomes Crotalus helleri
Crotalus oreganus lutosus becomes Crotalus lutosus.

The common names remain the same.

* Douglas, Douglas, Schuett, Porras, & Holycross
[2002. Phylogeography of the Western Rattlesnake (Crotalus viridis) Complex, With Emphasis on the Colorado Plateau]. Pp. 11-50. In Biology of the Vipers [Schuett, Höggren, Douglas, and Greene (editors). Eagle Mountain Publishing, Eagle Mountain, Utah]


According to Todd Battey, author of SoCal Herps, an electronic field guide to the reptiles and amphibians of Southern California, Northern Pacific Rattlesnakes that occur from the Carrizo Plains south along the western side of the San Joaquin Valley differ from others of the subspecies in having a yellow dorsal coloration, a large dose of mojavetoxin in the venom, and fewer large scales between the supraoculars. This form is called the "Carrizo Yellow" form and may be distinct enough to be considered a separate subspecies.

Alternate and Previous Names (Synonyms)

Timber Rattlesnake (It is not uncommon for a rattlesnake found in a forested area in California to be called a Timber Rattlesnake. The true Timber Rattlesnake (Crotalus horridus) is not found in California. It occurs from southeast Minnesota down to central Texas and east to northern Florida up to south-central New Hampshire.)

Mojave Green (Probably due to the green coloring on some Northern Pacific Rattlesnakes, they are sometimes called a Mojave Green, especially in the southern Sierra Nevada Mountains. The Northern Mohave Rattlesnake (aka Mojave Green) occurs only in the deserts south and east of the range of the Northern Pacific Rattlesnake.)


Crotalus oreganus oreganus - Northern Pacific Rattlesnake (Stebbins & McGinnis 2012, SSAR 2012)
Crotalus viridis oreganus - Northern Pacific Rattlesnake (Stebbins 1966, 1985, Klauber 1982, 2003)
Crotalus viridis oreganus - Pacific Rattlesnake (Black Rattlesnake) (Wright & Wright 1957)
Crotalus viridis oreganus (Stebbins 1954)
Crotalus viridis oreganus (Holbrook 1840)
Crotalus viridis (Rafinesque 1818)