University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln The Handbook: Prevention and Control of Wildlife Damage Management, Internet Center Wildlife Damage for January 1994 RATTLESNAKES (Crotalus viridis viridis) Walter E. Howard Professor Emeritus of Wildlife Biology and Vertebrate Ecology, Department of Wildlife, Fisheries and Conservation Biology, University of California, Davis, California 95616 Follow this and additional works at: https://digitalcommons.unl.edu/icwdmhandbook Part of the Environmental Sciences Commons Howard, Walter E., "RATTLESNAKES (Crotalus viridis viridis)" (1994). The Handbook: Prevention and Control of Wildlife Damage. 81. https://digitalcommons.unl.edu/icwdmhandbook/81 This Article is brought to you for free and open access by the Wildlife Damage Management, Internet Center for at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in The Handbook: Prevention and Control of Wildlife Damage by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Walter E. Howard Professor Emeritus of Wildlife Biology and Vertebrate Ecology RATTLESNAKES Department of Wildlife, Fisheries and Conservation Biology University of California Davis, California 95616 Fig. 1. Prairie rattlesnake, Crotalus viridis viridis Introduction Trapping Damage Prevention and Rattlesnakes are distinctly American Control Methods* Effective in some situations when serpents. They all have a jointed rattle properly placed. at the tip of the tail, except for one rare Exclusion Glue boards are useful in removing species on an island off the Mexican Construct a snake-proof fence around rattlesnakes from buildings. coast. This chapter concerns the genus areas of human activity. Crotalus, of the pit viper family Shooting Crotalidae, suborder Serpentes. Since Seal entrances to buildings and snakes evolved from lizards, both structures. Effective where safe. groups make up the order Squamata. Habitat Modification Other Methods This article describes the characteris- Eliminate shelter for snakes. Organized snake hunts may be tics of the common species of rattle- successful in spring or early snakes that belong to the genus Control rodents; they attract snakes. summer. Crotalus. These include the eastern Repellents Snake Bite diamondback, (C. adamanteus); the None are available. western diamond (back) rattlesnake, Wear protective clothing and be (C. atrox); the red diamond rattlesnake, Toxicants careful when climbing and walking. (C. ruber); the Mohave rattlesnake, None are available. If a bite occurs, keep the victim calm, (C. scutulatus); the sidewinder, (C. warm, and reassured. Seek medical ceraster); timber rattlesnake, (C. Fumigants attention immediately. horridus); three subspecies of the west- Generally not effective in dens. ern rattlesnake, (C. viridis): the prairie rattlesnake (C. v. viridis); the Great Basin rattlesnake (C. v. lutosus); and *Information pertains to other poisonous snakes. the Pacific rattlesnake (C. v. oreganus). PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994 Cooperative Extension Division Institute of Agriculture and Natural Resources University of Nebraska - Lincoln United States Department of Agriculture Animal and Plant Health Inspection Service Animal Damage Control F-21 Great Plains Agricultural Council Wildlife Committee There are 15 species of rattlesnakes in Elliptical eye pupil the United States and 25 in Mexico. Other front-fanged poisonous snakes of the Crotalidae family, which are not Nostril included in this discussion, are the massasauga and pigmy rattlesnakes, both of the genus Sistrurus. Also not included are two snakes that do not have rattles, hence are not called rattle- snakes: the water moccasin or cotton- Loreal pit opens forward mouth, and the copperhead, both of the genus Agkistrodon. Two other gen- Fig. 2. Rattlesnake head showing “cat-eye” elliptical pupil and location of the large loreal pit, charac- teristic of pit vipers. era of poisonous snakes in North America are coral snakes (Micrurus black, chalky white, dull red, and olive or cannot be tracked after being struck. and Micruroides) of the family green. Many have diamond, chevron, One male rattler captured in the field Elapidae. or blotched markings on their backs had consumed 123% of its weight, but and sides. young rattlers frequently die due to Identification lack of food. Domestically raised rat- Range and Habitat tlesnakes will survive when fed only Rattlesnakes are usually identified once a year, but in the field, snakes by their warning rattle — a hiss or usually feed more than once, depend- Rattlesnakes occur only in North and buzz — made by the rattles at the tip ing on the size of prey consumed. A South America and range from sea of their tails. A rattlesnake is born with snake may kill several prey, one after level to perhaps 11,000 feet (over 3,000 a button, or rattler, and acquires a new another, and of different species. m) in California and 14,000 feet (4,000 rattle section each time it molts. Rattle- When rodents and rabbits are struck, m) in Mexico, although they are not snakes also are distinguished by hav- the prey is immediately released. The abundant at the higher elevations. ing rather flattened, triangular heads. snake then uses its tongue to track the They are found throughout the Great The heads of all Crotalus rattlesnakes prey to where it has died. Plains region and most of the United are about twice as wide as their necks. States, from deserts to dense forests Digestion is quite slow and usually no Only pit vipers possess this head con- and from sea level to fairly high moun- bones remain in the feces, called figuration; coral snakes do not. tains. They need good cover so they “scats.” Hair, feathers, and sometimes Rattlesnakes belong to the pit viper can retreat from the sun. Rattlers are teeth, however, can usually be identi- family Crotalidae, so named because common in rough terrain and wher- fied in scats. Rattlesnakes use very all possess visible loreal pits, or lateral ever rodents are abundant. little energy except when active, and heat sensory organs, between eye and they probably are active for less than nostril on each side of the head (Fig. 2). Food Habits 10% of their lives. They are not very These heat sensory pits are not present active unless food is scarce. They store in true vipers, which do not occur in Young or small species of rodents much fat in their bodies, which can last the Western Hemisphere. The facial comprise the bulk of the food supply them for long periods. pits enable rattlesnakes to seek out and for most rattlesnakes. Larger rattlers strike, even in darkness, warm objects may capture and consume squirrels, General Biology, such as small animal prey, as well as prairie dogs, wood rats, cottontails, Reproduction, and larger animals that could be a threat. and young jackrabbits. Occasionally, The vertically elliptical eye pupils, or even small carnivores like weasels and Behavior “cat eyes,” are also a characteristic of skunks are taken. Ground-nesting rattlesnakes (Fig. 2). Identifying a dead birds and bird eggs can also make up When a rattlesnake strikes its prey or rattler whose rattles are missing can be an appreciable amount of the diet of enemy, the paired fangs unfold from done by looking at the snake’s scales some rattlers. Lizards are frequently the roof of its mouth. Prior to the on the underside in the short region taken by rattlers, especially in the completion of the forward strike between the vent and the tip of the tail. Southwest. The smaller species of motion, the fangs become fully erect at If the scales are divided down the cen- rattlesnakes and young rattlesnakes the outer tip of the upper jaw. The ter, the snake is harmless. The scales regularly feed on lizards and amphib- erectile fangs are hollow and work like on rattlesnakes are not divided. ians. hypodermic needles to inject a modified saliva, the venom, into the Rattlesnakes come in a great variety of Rattlesnakes consume about 40% of prey. Rattlesnakes can regulate the colors, depending on the species and their own body weight each year. amount of venom they inject when stage of molt. Most rattlers are various Many prey are killed but not eaten by they strike. shades of brown, tan, yellow, gray, rattlesnakes because they are too large F-22 Mature fangs generally are shed sev- Opening to hollow eral times a season. They may become fang is a groove on outer surface embedded in the prey and may even be swallowed with the prey. When one mature fang in a pair is lost, it will soon be replaced by another functional mature fang. A series of developing Replacement fangs fangs are located directly behind one in sheath another in the same sheath at the roof and outer tip of the mouth (Fig. 3). If a Right venom newly replaced fang is artificially gland removed, it may require weeks or longer before another replacement will Teeth be fully effective. One fang can func- tion, however, while the other in the pair is being replaced. Fangs that get stuck in a person’s boot are not very dangerous; they cannot contain much venom since they serve only as a hol- low needle. The external opening of the hollow fang is a groove on the out- side of the fang, set slightly back from the tip to prevent it from becoming plugged by tissue from the prey (Fig. 3). Fig. 3. Head of a rattlesnake in striking position. Supple- Rattlesnakes cannot spit venom, but mentary fangs are covered by a sheath of tissue. Each the impact of a strike against an object fang is located in a double socket. Replacement fangs appear in what are currently empty sockets. can squeeze the venom gland, located in the roof of the mouth, and venom may be squirted. This can happen when a rattler strikes the end of a stick long as a year. During summer, preg- scopic particles from the environment pointed at it, or the wire mesh of a nant females usually do not feed, so to sensory cells in pits at the roof of the snake trap.