Western Rattlesnake (Crotalus viridis)
By Jordan Loughmiller
Photo by Charles Peterson
Taxonomy
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
Identification
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.
Distribution
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
Habitat
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.
Behavior
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.
Reproduction
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
Methods
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.
Results
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.
Refrences
Digital Atlas of Idaho
http://imnh.isu.edu/digitalatlas/
Feeding Ecology of the Rattlesnake, Crotalus viridis oreganus, in Northern Idaho
Richard L. Wallace, Lowell V. Diller
Journal of Herpetology, Vol. 24, No. 3 (Sep., 1990), pp. 246-253
doi:10.2307/1564390
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