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A Guide to the Amphibians
and Reptiles of California





Identifying subspecies of Adult Western Rattlesnakes
(Crotalus oreganus) in California

 









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Venomous and Potentially Dangerous!
Usually you can determine the subspecies of a western rattlesnake found in California by looking at where it was found on a range map such as the one below.
map
Range of Western Rattlesnake - Crotalus oreganus
Blue: Crotalus oreganus helleri -  Southern Pacific Rattlesnake

Orange: Crotalus oreganus lutosus -  Great Basin Rattlesnake

Red: Crotalus oreganus oreganus - Northern Pacific Rattlesnake

Below are some of the key markings on the three subspecies of Crotalus oreganus that are also supposed to help to differentiate the subspecies (following the texts referenced below) however they are not always conclusive.

The most reliable mark in the majority of C. o. oreganus and C. o. helleri that I have compared is the width of the terminal dark tail ring. (The difference in contrast of the tail rings is often unconclusive, as is measuring the location where the blotches transition into body and tail bands.)

C. o. lutosus
can usually be identified by the light ground color and the light spaces in the dark blotches.

Southern Pacific Rattlesnake - Crotalus oreganus helleri

The last dark ring by the rattle is at least twice as wide as the preceding bands.

(Sometimes this ring is brown or yellowish)
southern pacific rattlesnake© 2006 Steve Broggie southern pacific rattlesnake© Koby Poulton rattle

rattle

rattle

rattle© Chris Gruenwald
     
Dark blotches on the back and sides of the body transition to
bands and tail rings at approximately the last fifth (20 percent) of the body length.

(Generally there is not much contrast between the dark and light tail rings - but this is not always a great field mark to use.)
southern pacific rattlesnake
© 2006 Steve Broggie
southern pacific rattlesnake

southern pacific rattlesnake© Patrick Briggs
Dorsal and side blotches transition to bands at about the last fifth (20 percent) of the body.

This is a juvenile snake, but the number of blotches and bands will not change as it ages. The full-body shot here lets you see where the dorsal blotches transition to bands.

The dorsal and side blotches to transition to bands at about the last fifth (20 percent) of the body.
Northern Pacific Rattlesnake - Crotalus oreganus oreganus
 
The last dark ring by the rattle is not noticeably wider than the preceding bands.
rattle rattle rattle
rattle rattle rattle
     
Dark blotches on the back and sides of the body transition to
bands and tail rings at approximately the last third (33.33 percent) of the body length. 

(Generally there is a high-contrast between the dark and light tail rings - but this is not always a great field mark to use.)
northern pacific rattlesnake northern pacific rattlesnake northern pacific rattlesnake
     
Great Basin Rattlesnake - Crotalus oreganus lutosus
 

Tail is ringed with the last dark ring by the rattle wider than the other dark rings and almost black.

rattle
rattle  
     

Dark blotches on the back and sides of the body usually have light centers.
(Those on C. o. oreganus and C. o. helleri do not.)

Ground color is lighter than on other subspecies - light gray, pale yellow, buff, or tan.

great basin rattlesnake great basin rattlesnake great basin rattlesnake
     
References

Klauber, Laurence M. Rattlesnakes. University of California Press. (Abridged from the 1956 two volume Rattlesnakes: Their Habits, Life Histories, and Influence on Mankind.) University of California Press, 1982.

Stebbins, Robert C., and McGinnis, Samuel M.  Field Guide to Amphibians and Reptiles of California: Revised Edition (California Natural History Guides) University of California Press, 2012.

Stebbins, Robert C. California Amphibians and Reptiles. The University of California Press, 1972.

Hubbs, Brian R., & Brendan O'Connor. A Guide to the Rattlesnakes and other Venomous Serpents of the United States. Tricolor Books, 2011.

Bartlett, R. D. & Patricia P. Bartlett. Guide and Reference to the Snakes of Western North America (North of Mexico) and Hawaii. University Press of Florida, 2009.



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