Western Rattlesnake

Great Basin Rattlesnake:
Picture from the Utah Division of Wildlife Resources

Rattlesnakes are venomous and should be treated with respect.

Western rattlesnakes are habitat generalists and are widely distributed over the western United States. They tend to like rocky areas in drier regions. There are three subspecies of western rattlesnake, the prairie rattlesnake, Great Basin rattlesnake and the Pacific rattlesnake. Can you guess which subspecies occurs in the Basin and Range region? That's right the Paci...no, no, no the Great Basin rattlesnake (Crotalus viridis lutosus), of course. 

Even though rattlesnakes are called “cold-blooded”, their muscles and digestion work best at warm body temperatures, so these reptiles bask in the sun or lie on warm surfaces until they are 80-90 F.   Western rattlesnakes vary greatly in color, but tend to be camouflaged, consisting of browns and grays, but they can also have greenish and yellowish hues. They have darker rings or splotches along their dorsal or back side. 

Often, the first sign that you have come across a rattlesnake is the telltale sound they make with their rattles. I've come across them several times and to me, the rattling noise sounds similar to a running faucet. Rattlesnakes rattle their tail when they feel threatened, so typically they give hikers and other recreationalists a rattling warning before they are within striking distance--not always though and they don't always give a warning rattle.  The rattling noise comes from a series of rattles at the end of their tail. Rattles are added each time the snake sheds its skin, which is typically 1-3 times a year.  Counting rattles is not a good way to age snakes, as rattles can break off and the variability in shedding.  They give birth to live young, but the young can't produce a rattling noise until they have shed at least three times. 

Rattlesnakes have a large, triangle shaped head with a narrow neck. The size and shape of their head is due to the bulkiness of their venom glands and the large muscles that control them.  Their fangs drop and extend forward when they strike.  Venom is then dispensed through their fangs, which are hollow and have slits in the front to envenom their prey.  The venom is a toxin that subdues their prey and helps with digestion.  When not striking, the fangs fold back against the roof of their mouth.  Their jaws are very flexible and the segments are loosely connected allowing the lower jaw to "unhinge"  which then allows them to swallow fairly large prey.  Rattlesnakes typically prey on small mammals such as mice and squirrels, but have also been known to eat birds, lizards and eggs.

All rattlesnakes are in the subfamily viperidae, also known as the pit vipers.  The snakes in this subfamily have sensory pits on either side of their head. These sensory pits are heat sensitive and help rattlesnakes locate prey in low light and even in complete darkness.  

Sources and further reading:
M.L. Robinson, P.M. Conrad, and M.M Ryan. 2007. Venomous Reptiles of Nevada.  University of Nevada Cooperative Extension-Nevada Department of Wildlife Partnership Pub. SP-07-07

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