Crotalus oreganus oreganus near its southern range limit is variable in appearance, often looking very much like C. o. lutosus. An example is the Kern County snake seen in the row above. Identification of rattlesnakes found in this region can be confusing and open to debate. Some of these controversies should be resolved when the results of further studies on these species are published.
According to Robert Hansen who has studied the area in depth: "Among populations of "oreganus" inhabiting arid landscapes near their southern range limits (e.g., southern San Joaquin Valley, Carrizo Plain), there is a tendency toward small size, light ground color, and reduced dorsal blotch size...features that cause these snakes to superficially resemble lutosus."..."The southern extent of the range of lutosus in eastern California (e.g., the Mono/Inyo counties region) has been mapped in reasonable detail, and thus far, there are no known instances where the ranges of oreganus and lutosus come into contact.
However, farther north, where the Sierra Nevada crest is much lower and the potential for populations of oreganus and lutosus to meet is likely greater, careful field studies are lacking. Ultimately, reliance on features of coloration and pattern to distinguish one form from the other in areas of potential contact is not advised."
Click on the picture to see more rattlesnake signs.
Rattlesnakes are important members of the natural community. They will not attack, but if disturbed or cornered, they will defend themselves. Reasonable watchfulness should be sufficient to avoid snakebite. Give them distance and respect.
"Rattlesnakes are also among the most reasonable forms of dangerous wildlife: their first line of defense is to remain motionless; if you surprise them or cut off their retreat, they offer an audio warning; if you get too close, they head for cover. Venom is intended for prey so they're reluctant to bite, and 25 to 50 percent of all bites are dry - no venom is injected."Leslie Anthony. Snakebit: Confessions of a Herpetologist. Greystone Books, 2008.
Rattlesnake bites can be extremely dangerous, but rattlesnakes should not be considered as vicious and always ready to attack without provocation. They will not strike without a reason, but they will aggressively defend themselves. They are often portrayed with the body partly coiled, the tail rattling loudly, and the head up ready to strike. This display is a warning not to come any closer or they will strike; a defensive behavior that some rattlesnakes use when they sense that crawling away would put them in danger. If they are given some space and some time to escape to a safe place, they will usually crawl away as fast as possible.
Because they cannot crawl to safety as fast as some snakes, rattlesnakes often use their cryptic color and pattern to blend into their surroundings in order to hide from their prey and from other animals that could threaten them. They often hunt by sitting still and waiting for a warm-blooded prey animal to pass close enough for the snake to strike it. Sometimes a passing human will be struck instead, mistaken for food. When they sense the presence of something that might threaten them, rattlesnakes often lie still to avoid detection and do not rattle, because that would give away their location. At other times they rattle loudly, sometimes from a good distance, to warn potential enemies of their presence. In both cases they are doing everything they can to avoid confrontation and to avoid striking and biting and using up their valuable supply of venom which they need to kill and digest their food.
The venom of this snake is potentially dangerous to humans.
Adults of this species range from 15 - 65 inches long, ( 38 - 165 cm) but typically the adults seen are 3 - 4 feet long. Newborns are around 10 inches long.
A heavy-bodied, venomous pit viper, with a thin neck and a large triangular head. Pupils are elliptical. Scales are keeled. Two light stripes extend diagonally across the sides of the head, but they are sometimes faded and not evident.
The ground color is variable, matching the environment - pale grey, tan, light yellow, buff colored. The back is marked with dark blotches with light centers, usually in the shape of bars or ovals, about as wide as the spaces between them. The underside is pale, sometimes weakly mottled.
The tail is barred, and without white rings. A rattle, consisting of loose interlocking segments, usually occurs at the end of the tail. A new rattle segment is added each time the skin is shed. Newborn snakes do not have a rattle - just a single button which does not make a sound.
Heat sensing pits on the sides of the head help the snake to locate prey by their warmth. Long, hollow, movable fangs connected to venom glands inject a very toxic venom which quickly immobilize prey. The snake can control the amount of venom injected and the fangs are replaced if broken. Bites on humans are potentially dangerous without immediate medical treatment. Even a dead snake can bite and inject venom if the jaws reflexively open when they are touched.
Primarily nocturnal and crepuscular during periods of excessive daytime heat, but also active during daylight when the temperature is more moderate. Not active during cooler periods in Winter.
Prey is found while the snake is actively moving, or by ambush, where the snake waits near lizard or rodent trails, striking at and releasing passing prey. The snake then follows the trail of the envenomated animal and swallows it whole.
When alarmed, a rattlesnake shakes its tail back and forth. The movement rubs the rattle segments together producing a buzzing sound which serves as a warning. Juveniles are born with only a silent button at the end of the tail.
Eats small mammals, including ground squirrels, mice, rats, rabbits and hares, birds, lizards, snakes, frogs, and insects.
Bears live young.
This subspecies, Crotalus oreganus lutosus - Great Basin Rattlesnake, is found in California in the far northeastern corner and in a small region east of the Sierras near the Mono Lake area. It continues outside the state north into eastern Oregon, and east to western Utah, southern Idaho, most of Nevada, and barely into extreme northwestern Arizona.
The species Crotalus oreganus - Western Rattlesnake, occurs from the Pacific Coast of northern Baja California north through most of California except the southern deserts, through Oregon and eastern Washington into British Columbia, Canada, and east into Nevada, Idaho, Utah, northern Arizona, extreme southwestern Wyoming, and extreme northwestern New Mexico.
Elevation record of 12,112 ft. (3962 m.) Wheeler Peak, Great Basin National Park, White Pine County, Nevada. (Herpetological Review 41(1), 2010)
The taxonomy of Western Rattlesnakes is controversial and still being studied.
Some researchers still use the former species name Crotalus viridis and for them this snake remains Crotalus viridis lutosus .
In a 2002 study, 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]
split C.viridis into 7 distinct species:
Crotalus - Greek - krotalon - a rattle - refers to the rattle on the tail
oreganus - belonging to the state of Oregon - referring to the type locality, "banks of Oregon or Columbia River" lutosus - Latin - muddy, full of mud - referring to the brownish dorsal color
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.)