The Prairie Rattlesnake

“Crotalus viridis”

Wyoming’s Pit Viper

The Prairie rattlesnake is the most widely distributed rattler in the Western United States and Canada with nine varieties or subspecies.

Two of these subspecies reside in Wyoming.

The traditional Prairie rattlesnake is found over most of Wyoming while it’s cousin, the Midget Faded rattler, lives in southwestern Wyoming. The common Prairie rattlesnake may reach a length of about 3.5 feet while the smaller Midget Faded grows only to 22 inches.

Both varieties can be found in a variety of geographical terrain including; woodlands, scrub areas, prairie grasslands, sand dunes, and rocky outcropping that afford a southern exposure. Many rattlesnakes will take up residency in a prairie dog town for the summer months.

All rattlesnakes are pit vipers, which means they have the ability to detect heat from other animals. If you were to blindfold a rattler it would still be able to strike accurately as it can see an infrared image of you. This is how they hunt at night, much to the dismay of the rodents that are also active during the twilight hours!

Wyoming rattlesnakes will usually begin to emerge from their den or hibernaculum between April 23 and June 25 each year. The average date of emergence is May 28. Most rattlers remain close to their den for a few weeks before leaving for the summer, but Wyoming snakes frequently leave at once since we have such a short warm season. Upon departure, their primary goal is locating food. Their body weight is down 20-40 percent from their time spent hibernating. Rattlesnakes cannot reproduce properly if they are underweight. They may travel as far as five miles from their den in the search for a good feeding ground, however most rattlers remain within 2-3 miles of the hibcrnaculum. Once such an area is located, the snake will settle down and prowl it’s range. Unless prey animals become scarce, the snake will stay in it’s selected area until it returns to the den in the fall. This usually takes place in September. Upon their return, the snakes will stay near the mouth of the den to bask and feed when the weather permits. Once the ground temperature falls far enough, the rattlesnakes go into the hibernaculum and begin the long hibernation.

During the spring and fall months, most rattlers prowl and forage in the morning and afternoon hours. The midday hours are spent either basking or cooling in the shade depending on the air temperature. In the summer months when the days are very hot, the rattlesnakes usually take to nocturnal, or nighttime hunting. The mornings and evenings become the time of choice for basking.

The preferred food of Wyoming rattlesnakes is primarily rodents of one kind or another. This would include the various species of mice, gophers, squirrels, and shrews. Baby rabbits, rock chucks, and birds are also taken. On a lesser scale, amphibians and other reptiles are occasionally eaten. The Prairie rattlesnake is not immune to it’s own venom and there are documented cases of cannibalism. Predators of Wyoming rattlesnakes include badgers, coyotes, hawks, owls, and man.

When a rattlesnake locates a meal, it strikes the animal to envenomate it. The snake releases the prey and remains where it is at while the victim runs off to die. The venom actually starts the digestive process while the rattlesnake waits in complete safety. After a few minutes the snakes begins to flick it’s tongue rapidly and the search begins. Using it’s tongue and some very specialized organs located in the mouth, the rattlesnake follows the trail of the dying rodent. This trail may be interspersed with many other animal trails and odors but the snake has no difficulty in finding it’s victim. Once located, the snake will swallow the animal whole, usually starting at the head. It is now time for a basking session to aid the digestion.

Wyoming rattlesnakes give birth to live young instead of laying eggs like most reptiles. They’ll have 6-16 babies depending on the size of the female. The babies are usually born between August and October each year. The major cause of rattlesnake mortality in our state is the harsh winter months which causes the death of many baby rattlesnakes.

The defensive behavior of the Prairie rattlesnake generally goes like this: first, it remains motionless and depends on it’s cryptic coloration to escape detection. You cannot begin to imagine the number of rattlers you’ve walked right by due to this initial response! If this doesn’t work and the snake realizes it has been discovered, it will then attempt to crawl away from the threat. If it is further hassled, the snake will then coil, raise the upper portion of it’s body to a strike position, and try to back away from the threat while in a defensive position.

Did you know?

1. Approximately 1/3 of all rattlesnake bites in the field are “dry bites”, that is, no venom is injected. The rattlesnake has full control over the use of it’s venom. It prefers not to use it for defense as it’s primary function is for capturing prey.
2. A rattlesnake can strike at a distance equal to one third to one half of it’s body length. In Wyoming a person is safe from the largest of rattlesnakes by being only 24 inches away.
3. A rattlesnake can live up to 29 years in captivity and 15-20 years in the wild.
4. Baby rattlesnakes are not more venomous than the adults. The venom has the same toxicity on a drop for drop basis. Baby rattlers are very prone to bite due to the survival instinct imprinted in most young wild animals.
5. Removing a rattler’s fangs is of no use — it has back up fangs ready to go. It will go through several sets of fangs each season.
6. Rattlesnake are very good swimmers.

 

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