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western rattlesnake

Page history last edited by PBworks 12 years, 10 months ago


Western Rattlesnake (Crotalus viridis)

 By Jordan Loughmiller




Photo by Charles Peterson






Kingdom: Animalia

     Phylum: Chordata

          Class: Reptilia

               Order: Squamata

                    Suborder: Serpentes

                         Family: Viperidae

                              Subfamily: Crotalinae

                                   Genus: Crotalus

                                        Species: viridis

Subspecies found in Idaho: C.v. oreganus, C.v. viridis, C.v. lutosus







The Western Rattlesnake is easily distiguished from other Idaho herps.  The Western Rattlesnake may be confused for a Gopher snake, but upon


closer inspection they can be distiguished.  The Western Rattlesnake has a large triangular head that is contrasted by slenderbody at the poind of


head attachment.  The Western Rattlesnake has vertical pupils while the gopher snake has round pupils.  The Western Rattlesnake has a stout


muscular body and it also has its imfamous rattles.  The Gopher snake has a longer and more slender body in comperison to the  Western


Rattlesnake.  Western Rattlesnakes have highly keeled scales.  The Western Rattlesnake is a Pit Viper which means it has pit located near the


nostrils for infrared heat detection.





The Western Rattlesnake is found in most parts of the state of Idaho.  With the exception of the far northern parts of the state and the very high


elevations.  The Western Rattle snake is found throughout the western United States, South-western Canada and Northern Mexico. 




 Digital Atlas of Idaho




Western Rattlesnakes are predominantly found in drier regions in the state, but they can ofter be encountered in or near the riparian areas


that disect the state.  Rocky areas in the portions of the state that have sagebrush are usualy considered to be Rattlesnake habitat. 


Western rattlesnakes are not often found in areas with dense canopy cover. 





The Western Rattlesnake is well known for it alarm that is sounds off when it feels threatened.  The buzz of a Rattlesnakes' rattle is a warning to


all, back off!  The venom the is carried is used both for the procurment of food and also in defence it will strike out against a threat. 


A Rattlesnake will bite it's prey and injects a shot of venom at the same time.  They do not hold thier prey but instead they release them after


the bite.  The prey item goes off a short distance and dies.  The Rattlesnake follows the scent trail that is left behind by its prey after the bite. 


When the prey has been relocated the snake feeds apon the animal in its entirety.  The western Rattlesnake has multiple hinge points in its skull


and jaw that allow it to eat its prey whole. 





Western Rattlesnake young are born in the late summer and eary fall of the year.  The actual timing of birth depends on the area where the


snakes live.  Sexual maturity in Western Rattlesnakes is not reached until they are at least a few years old.  The areas that Western


Rattlesnakes live also affect how often they are able to reproduce, in parts of their far northern distribution they are only able to reproduce


every other year.



Scientific Study


Feeding Ecology of the Rattlesnake, Crotalus viridis oreganus, in Northern Idaho

Richard L. Wallace; Lowell V. Diller


            On the Columbia plateau in Northern Idaho is where the study to determine the feeding habits of Western Rattle snakes was preformed.   Snakes were captured by hand, with the aid of drift fences and by driving roads in order to locate snakes.  They were able to determine what the snakes had been eating by using a key to determine the remains of the prey species.  Sex and age classes were also determined.  They also determined if a female was pregnant, non-reproductive or post partum that year. 


            During their study they handled over 900 Western Rattlesnakes.  These snakes had fed upon eight mammal species, one lizard and one bird. The main species that were consumed were; voles, deer mice and mountain cottontails.  These four species were 92% of all prey that were consumed.  The main point that I gleaned from this article was that this population consumed different species then population in other areas; they were consuming what was available.   Western Rattlesnakes are a sit and wait predator and therefore they will eat what is abundant.





Digital Atlas of Idaho



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