The Prairie Rattlesnake

Notes on the captive maintenance of the Prairie rattlesnake

Crotalus viridis viridis

Natural History

The western rattlesnake, Crotalus viridis, has the most extensive range of any rattlesnake in the United States. It is a polytypic species with nine forms currently recognized although there is debate as to the validity of one or two races. The nominate race, Crotalus viridis viridis, is commonly referred to as the prairie rattlesnake. This subspecies has a wide distribution including Montana, Idaho, Wyoming, North Dakota, South Dakota, Colorado, Utah, Nebraska, New Mexico, Texas, Arizona, parts of Canada and Mexico.

The specimens of C. v. viridis in my collection originate from the state of Wyoming. While the largest C. v. viridis recorded was approximately 62 inches in length, the record for Wyoming is 52 inches. Males generally exceed the females in overall body length as well as body weight. The largest male in my collection is 46 inches in length.

Coloration is quite variable in C. v. viridis. Background colors can be green, yellow, grey, or brown. The blotched dorsal pattern is generally distinct and may be black, brown, or shades of grey. Each side of the face has two light colored stripes that run diagonally.

Preferred habitat is rather variable and is seasonally influenced. During the summer months the prairie regions are the usual choice while rocky outcrops with southern exposure are preferred in the autumn.

Natural specimens of C. v. viridis prey upon a wide variety of animals including rodents, birds, reptiles, amphibians, etc. Adults primarily feed upon endothermic prey while the young are more opportunistic in their feeding patterns. Young prairie rattlesnakes also seem to be more responsive to prey movement while the adults appear to utilize their vomeronasal capabilities to a greater degree.

Rattlesnakes in Wyoming are an important food source for the many raptor species that exist in the state as well as other predatory birds. The badger seems to have an affinity for snakes of any species and they take a dramatic toll upon local serpent populations. Interestingly, I have observed two instances of predation upon C. v. viridis by rainbow trout. Both of these cases involved fish caught by sportsmen that revealed young prairie rattlesnakes in the stomach of the fish. Both rattlesnakes were males and appeared to be less than two years old. This is not so surprising as the prairie rattlesnake is an accomplished swimmer and frequently crosses the many small waterways of Wyoming. Most riparian regions of the state are small and isolated by large expanses of prairie and C. v. viridis are attracted to these areas during years of low rodent populations as well as for hydration.

Prairie rattlesnakes in Wyoming may leave the hibernaculum area from late April through mid-June depending upon the weather conditions. Their return initiates in September and they remain close to the den area during the final autumn months where they feed and bask as weather permits. C. v. viridis is a gregarious animal regarding hibernation. Many years ago it was not uncommon to discover den sites that housed hundreds of specimens together. Den sites may also be shared with a variety of other wildlife.

Mating can take place in the autumn months beginning in August. It appears that C. v. viridis can retain sperm for long periods of time that may allow for genetic diversity as well as propagation efficacy in a hostile environment. C. v. viridis deliver their young in the fall. Neonates measure from 9-11 inches in length. Size and age of the female has a definite influence upon the size and number of young delivered with six being the average. In hostile environments, such as found in Wyoming, female C. v. viridis may give birth only every second or third year. It may take a female prairie rattlesnake 4-6 years to reach sexual maturity in northerly regions.

The venom of C. v. viridis should be considered quite toxic in its makeup although there are the expected variations from one population to another. Some races of C. viridis, including certain populations of C. v. viridis, possess the Mojave toxin like that of C. scutulatus. There is currently debate as to the toxicity of young pit vipers versus that of the adults. It is believed that as the rattlesnake matures the venom may exhibit different properties. This could be in response to a changing diet during the maturation process. While the venom of the young may not necessarily be more dangerous to humans than that of the adults, it should be remembered that neonatal rattlesnakes, as well as many other snake species, are quick to defend themselves and will frequently deliver multiple strikes at any target they feel threatened by. This behaviour can be logically attributed to a survival instinct inherent in an organism that is preyed upon by so many carnivores.

Captive Management

Captive maintenance of the prairie rattlesnake is not difficult for one with the requisite experience pertinent to venomous serpent husbandry. Most specimens acclimate in a short period of time, handle well on hooks, and accept previously killed or thawed rodents as food. Captive propagation is easily realized with C. v. viridis.

Recently caught prairie rattlesnakes can exhibit an incredibly hostile attitude, however, many specimens calm down appreciably in just several weeks. There are, of course, those individuals that fail to acclimate regardless of conditions or time allowances. New additions to my collection are maintained in quarantine for several weeks to evaluate temperament as well as health. During this time the animal is kept isolated from the general reptile facility in a spartan exhibition type of cage that is thoroughly disinfected prior to use. All handling is done with disposable gloves to avoid, within reason, transmission of pathogens. If the animal does not appear to settle down in the time frame allotted, it is returned to the area of capture at a similar time of day as when it was taken. All transport containers are disinfected with a 5% hypochlorite solution. Fecal exams are done for common nematodes, trematodes, etc. No antihelminthics are administered until the rattlesnake demonstrates an acceptance of captivity.

Housing

I maintain adult pairs in enclosures that have a floor area of eight square feet, (48" x 24"). Substrate is aspen shavings at a depth of 2 inches. Heat is provided at one end of the cage via an overhead ceramic globe. This is directed down upon a pile of flat rocks that provide a naturalistic basking zone. This heater runs on a 12-hour daily cycle. When the ceramic heater shuts off at night, the rocks have absorbed an appreciable amount of heat which the rattlesnakes take advantage of. Additionally, a heating pad is located under the rocks and substrate to afford a constant source of gentle heat to the rocks and it runs continuously. A standard incandescent bulb provides supplemental lighting and is synchronized with the natural light cycles by using a photoelectric switch. Daytime air temperatures are 86 F. at the warm end and 78 F. at the cool end. Nighttime air temperatures fall to 73 F. The heating pad under the rocks allows a contact basking temperature of 80 F. throughout the night for use by specimens that have fed heavily and reproductive females.

Two water receptacles are provided, one at the cool end of the cage and one in the middle area of the enclosure. The receptacles are large plastic canine food dishes that have openings on the sides to allow finger access when picking them up. I use this style so the water receptacle doubles as a hide box for the rattlesnakes, which enter via the side openings.

Feeding

I use frozen rodents exclusively with C. v. viridis. Occasionally, a neonate may require a little teasing with its first few meals and will then usually feed freely soon afterward. Specimens are removed from multiple occupant enclosures and fed singly to avoid accidents. I use a beverage cooler to isolate the specimens while they feed. Body weight is maintained by visual inspection and subsequent dietary adjustment. Feeding schedules are adjusted with regard to age, season, and reproductive activity as well. Captive rattlesnakes easily become obese which probably shortens their lifespan and may inhibit reproductive activity.

Captive Propagation

The prairie rattlesnake, when properly acclimated, reproduces regularly in captivity. I have not found it necessary to implement a formal hibernation in order to stimulate sexual behaviour. My specimens are fed through October with the first two weeks of November being used for final digestion and elimination. In mid-November the animals are removed from the enclosure and placed singly in secure tubs with aspen bedding. They are then placed in a room that has a temperature range of 58-62 F. Water is offered every two weeks. This continues through the end of March. The tubs are then brought out of the cool room and allowed to warm up to the normal room temperature of 73 F. After a few days of room temperature, the animals are placed within their respective enclosures. Males are fed weekly and reproductive females are fed twice per week. Co-habitation is allowed throughout July.

In early August, I remove the males and leave the females in their cages. The males are placed singly in a separate enclose that is for breeding only. This segregation allows me to track genetics to a degree. Courtship initiated by the male usually occurs rapidly with exploratory tongue flicks, venter investigations, and spastic locomotion. Subsequent copulation generally lasts for several hours. After copulation, the female is placed in a "gravid" enclosure that houses other impregnated females and is set up in the same manner as the co-habitation cage. C. v. viridis seems to pay little attention to photographic documentation during copulation, even when powerful flash equipment is involved.

Young are generally born in August or September. Females are fed small prey items at 48-hour intervals following delivery to regain body weight. Well-maintained females will reproduce annually after they are in captivity for a few years. Litter sizes from captive specimens are usually greater in number than those of their natural counterparts and the neonates are somewhat larger as well.

Neonates usually shed within one week or so and are then offered thawed pink mice. The initial feedings are done in a small plastic tub style container with the snake and pink mouse left overnight undisturbed. I do not cool my young prairie rattlesnakes for the first two years in order to expedite sexual maturity. "Power" feeding is avoided.

During those years that reproductive activity is not desired, supplemental lighting is discontinued entirely. Cages are oriented to disallow any influence of facility windows regarding light cycles. Gender separation is, of course, the most effective means of preventing unwanted offspring.

In Summary

C. v. viridis is a very successful pit viper that is found in a variety of habitats and exhibits a great deal of color variation. A medium sized rattlesnake that adapts well to captivity, the prairie rattler has lent much to our science in the way of behavior studies. It is an excellent species to use for public demonstration as it is easily manipulated yet aggressive enough to hold its ground in a defensive manner for exhibition purposes. Captive propagation is reliable enough to justify wild capture only for scientific study or genetic diversification. It is a most beneficial animal within its environment both from a pest control aspect as well as an important food source.

Suggested Reading

Rubio, M. 1998. Rattlesnake. Smithsonian Institution Press. 240 pp.

Ernst, C. H. 1992. Venomous Reptiles of North America. Smithsonian
Institution Press. 236 pp.

Schuett, G. W. 1992. Is long-term sperm storage an important component of the reproductive biology of temperate pitvipers? Biology of the Pitvipers.
Selva. pp. 169-184.

Seigel, R. A. and Collins, J. T. 1993. Snakes: Ecology and Behavior.
McGraw-Hill. 414 pp.

Klauber, L. M. 1956, 1972, 1997. Rattlesnakes: Their Habits, Life Histories, and Influence on Mankind. 2 vols. University of California
Press. 1533 pp.

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