rattlesnake

Rattlesnake
Crotalus cerastes
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Suborder:	Serpentes
Family:	Viperidae
Subfamily:	Crotalinae
Genus:	Crotalus Linnaeus, 1758
Genus:	Sistrurus Garman, 1883
Species
27 species; see list of rattlesnake species and subspecies.

Rattlesnakes are a group of venomous snakes, genera Crotalus and Sistrurus. They belong to the subfamily of venomous snakes known commonly as pit vipers.

Overview

There are approximately thirty species of rattlesnake, with numerous subspecies. They receive their name for the rattle located at the end of their tails. The rattle is used as a warning device when threatened. The scientific name Crotalus derives from the Greek, κρόταλον, meaning "castanet". The name Sistrurus is the Latinized form of the Greek word for "tail rattler" (Σείστρουρος, Seistrouros) and shares its root with the ancient Egyptian musical instrument, the sistrum, a type of rattle. Most rattlesnakes mate in the spring. All species give live birth, rather than laying eggs. The young are self-sufficient from birth. Since they do not need their mother after birth, the mother does not remain with her young. However, at least one captive study has demonstrated that females and their neonates show some level of affinity for each other's company and will cross barriers to reunite if separated.^{[citation needed]}

Contrary to popular myth, rattlesnakes are not deaf. In fact, the structure of their inner ears is very much like that of humans. They do, however, lack external ears. Sound (whether from air or ground vibration) is transmitted to the snake's inner ear via bone and muscle.^{[citation needed]}

Prey

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Rattlesnakes consume mice, rats, small birds and other small animals. They subdue their prey quickly with a venomous bite as opposed to constricting. The venom will immediately stun or kill typical prey. Rattlesnake venom can kill in 20 seconds, but a rattlesnake will follow prey that does not quickly succumb to the venom and attempts to escape. Rattlers are known to strike at distances up to two-thirds their body length.

Reproduction

Although many kinds of snakes are oviparous (lay eggs), rattlesnakes are ovoviviparous -- the female retains the eggs in her body and they hatch as they are laid or soon afterwards; or viviparous (give birth to live young). Baby snakes are ready to go as soon as they are hatched or born. There is little to no parental care of the newborn snakes.

Rattle

The rattle of a rattlesnake

Drawing of the rattle

The rattle is composed of a series of nested, hollow beads which are actually modified scales from the tail tip. Each time the snake sheds its skin, a new rattle segment is added. They may shed their skins several times a year depending on food supply and growth rates. Newborn rattlesnakes (pre-button) do not have functional rattles; it isn't until after they have shed their skin for the first time that they gain an additional bead, which beats against the first bead, known as the button, to create the rattling sound. Adult snakes may lose their rattles on occasion, but more appear at each molting. If the rattle absorbs enough water in wet weather, it will not make noise.

Safety and identification

Juvenile Southern Pacific Rattlesnake in California

Different species of rattlesnake vary significantly in size, territory, markings, and temperament. If the rattlesnake is not cornered or imminently threatened, it will usually attempt to flee from encounters with humans, but will not always do so. Bites often occur when humans startle the snake or provoke it. Those bitten while provoking rattlesnakes have usually underestimated the range (roughly two-thirds of its total length) and speed with which a coiled snake can strike (literally faster than the human eye can follow). Heavy boots and long pants reinforced with leather or canvas are recommended for hikers in areas known to harbor rattlesnakes.

Guides are available through booksellers, libraries, and local conservation and wildlife management agencies that aid hikers and campers in identifying rattlesnakes. The advice given is to avoid contact with rattlesnakes by remaining observant and not approaching the animals. Hikers are advised to be particularly careful when negotiating fallen logs or boulders and when near rocky outcroppings and ledges where rattlesnakes may be hiding or sunning themselves. However, snakes will occasionally sun themselves in the middle of a trail, so such areas are not the only places where they are encountered. When encountering a rattlesnake on a trail, hikers are advised to keep their distance and allow the snake room to retreat.

Bites

A rattlesnake warning sign

Rattlesnakes are born with fully functioning fangs capable of injecting venom and can regulate the amount of venom they inject when biting. Generally they deliver a full dose of venom to their prey, but may deliver less venom or none at all when biting defensively. A frightened or injured snake may not exercise such control. Young snakes are to be considered more dangerous, as they have less control over the amount of venom they inject.^[1] A young rattlesnake will often simply inject all its venom, which might be a lethal dose, depending on the size of the bitten animal.

Toxicity

Most species of rattlesnakes have hemotoxic venom, destroying tissue, degenerating organs and causing coagulopathy (disrupted blood clotting). Some degree of permanent scarring is very likely in the event of a venomous bite, even with prompt, effective treatment, and a severe envenomation, combined with delayed or ineffective treatment, can lead to the loss of a limb or death. Thus, a rattlesnake bite is always a potentially fatal injury. Untreated rattlesnake bites, especially from larger species, are very often fatal. However, antivenom, when applied in time, reduces the death rate to less than 4%. It is estimated that between 7,000 and 8,000 people are bitten by venomous snakes in the United States each year, and about five of those die.^[2] About 72% of those bitten by rattlesnakes are male.^[3]

Some rattlesnakes, especially the tropical species, have neurotoxic venom. A bite from these snakes can interfere with or shut down parts of the nervous system. In the U.S. the Mojave Rattlesnake (Crotalus scutulatus) in Arizona and parts of California has a neurotoxic venom component known as Mojave Type A toxin. The current antivenom, (FDA-approved in October, 2000) known as Cro-Fab, contains antibodies to Mojave A and B toxins as well as the toxins of most other U.S. pit vipers. Mojave A toxin has been identified present in the venoms of other species of rattlesnakes on occasion. Neurotoxins cause neurological symptoms, paralysis and could result in death due to respiratory paralysis. In the U.S., Central and South America there are another group of neurotoxic snakes known as the Coral Snakes, not related to rattlesnakes but more closely related to the cobra family of Africa and Asia. These snakes can also cause death due to respiratory paralysis if not properly treated.

The Common Kingsnake (Lampropeltis getula), a constrictor, is famous for being largely immune to the venom of rattlesnakes and other vipers,^[4] and therefore rattlesnakes form part of this snake's natural diet in the wild.

Timber Rattlesnake (Crotalus horridus)

First aid

When a bite occurs, the amount of venom injected cannot be gauged easily. Symptoms and swelling may occur quickly, and may cause death easily but in some cases hours may pass before serious effects appear.

Experienced health workers typically gauge envenomation in stages ranging from 0, when there is no evident venom, to 5, when there is a life-threatening amount of venom present. The stages reflect the amount of bruising and swelling around the fang marks and the speed with which that bruising and swelling progresses. In more severe envenomation cases (stage 4 or 5) there may also be proximal symptoms, such as lip-tingling, dizziness, bleeding, vomiting, or shock. Difficulty breathing, paralysis, drooling, and massive haemorrhaging are also common symptoms.

Quick medical attention is critical, and treatment typically requires antivenin/antivenom to block the tissue destruction, nerve effects, and blood-clotting disorders common with rattlesnake venom. Most medical experts recommend keeping the area of the bite below the level of the heart. It is important to keep a snake bite victim calm in order to avoid elevating their heart rate and accelerating the circulation of venom within the body. Untrained individuals should not attempt to make incisions at or around bite sites, or to use tourniquets, as either treatment may be more destructive than the envenomation itself.

Any bite from a rattlesnake should be regarded as a life-threatening medical emergency that requires immediate hospital treatment from trained professionals.

Human consumption

Rattlesnakes are also a popular food in some southeastern and southwestern American cuisines and are sometimes sold in specialty meat shops.^[5] The flavor has been characterized by one vendor as "delicate" and "resembling chicken";^[6] and by journalist Alistair Cooke as "just like chicken, only tougher."^[7] Others have compared the flavor to a wide range of other meats, including veal, frog, tortoise, quail, fish, rabbit, and even canned tuna.^[8]

Captivity

There are fairly obvious risks with private ownership of rattlesnakes. A bite can cause death or permanent disability. Even a nonfatal bite can lead to very high costs for emergency medical care.^[9] Some jurisdictions outlaw the possession of venomous snakes. Where it is legal, some form of license or insurance policy may be required.^[10]

Media

	Rattlesnake sound of a rattlesnake
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See also

• List of crotaline species and subspecies

References

• Manny Rubio; Rattlesnake: A Portrait of a Predator; Smithsonian Institution Press; ISBN 1-56098-808-8 (hardcover, 1998)
• R. Burton, MD; Emergency Medicine. Lectures on Venom and Toxins. 1989.

External links

Look up rattlesnake in Wiktionary, the free dictionary.

Wikimedia Commons has media related to: Crotalus

Wikisource has the text of the 1911 Encyclopædia Britannica article rattlesnake.

• J. Jones, MD; Dispelling The Snakebite Myth
• Desert USA article
• American International Rattlesnake Museum Albuquerque, New Mexico
• Rattlesnakes of Arizona Good descriptions of many species with ranges
• Western Diamondback Rattlesnake Facts & Photos
• Victim's account of rattlesnake bite - Crotalus scutulatus
• Victim's account of rattlesnake bite - Crotalus horridus
• California Rattlesnakes
• Facts about snakes in California