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

# Overview
There are approximately fifty species of rattlesnake, with numerous subspecies. They receive their name for the rattle located at the tip of their tails.  The rattle is used as a warning device when threatened. The scientific name Crotalus derives from the Greek, , meaning "castanet".  The name Sistrurus is the Latinized form of the Greek word for "tail rattler" (, 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. As they do not need their mother after birth, the mother does not remain with her young.

# Prey
Rattlesnakes consume rodents and other small animals, such as rabbits, rats, mice, etc., subduing their prey quickly with a venomous bite as opposed to constricting.  The venom stuns or kills typical rattlesnake prey immediately. A rattlesnake will follow prey that does not quickly succumb to the venom and attempts to escape. They are specially known to strike at distances up to two-thirds their body length.

# Predators
Rattlesnakes are prey for kingsnakes, roadrunners, pigs, hawks, and eagles. They have been harvested as human food, such as at the Rattlesnake Round-Up in Sweetwater, Texas.

# 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.  The rattle may break; there is little truth to the claim that one can tell a rattlesnake's age from the number of beads in its rattle. Newborn rattlesnakes 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.

# Paleontology
The earliest fossil found which can be definitively identified as a rattlesnake was discovered near Driftwood Creek in Hitchcock County, Nebraska, U.S.A. An exact age of the specimen is indeterminate. The fossilized remains usually consist of ribs, which makes accurate specie identification problematic, as even many species of modern rattlesnakes have nearly identical vertebral characteristics. One extinct species, of which fossils were discovered in Allen Cave in Citrus County, was given the name Croeus. Though it had many characters in common with the modern Crotalus adamanteus, it was a much larger animal, probably attaining lengths in excess of 12 feet. In general, the fossil record for rattlesnakes is quite limited, and their exact route of evolution from the more primitive true vipers to their current form is not well understood.

# Safety and identification
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).  Be aware that they can actually strike without pulling their body back. Heavy boots and long pants reinforced with leather or canvas are recommended when hiking in areas known to harbor rattlesnakes.
For learning how to quickly and safely identify rattlesnakes by their markings, guides are available through booksellers, libraries, and local conservation and wildlife management agencies.  The best way to avoid contact with rattlesnakes is to remain observant and avoid potential encounters.  Hikers should always watch their steps when negotiating fallen logs or boulders and take extra caution when near rocky outcroppings and ledges where rattlesnakes may be hiding or sunning themselves. Snakes will occasionally sun themselves in the middle of a trail, so always watch your step. When encountering a rattlesnake on a trail, keep your distance and allow the snake room to retreat.

# Rattlesnake bites
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, although incapable of delivering an amount of venom equivalent to their adult counterparts, are still potentially deadly. Any bite must be considered dangerous and professional medical care should immediately be sought.

## 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 and rarely, death.  Thus, a rattlesnake bite is always a potentially serious, or even fatal, injury. Untreated rattlesnake bites, especially from larger species, are very often fatal. However, antivenin, when applied in time, reduces the death rate to less than 4%. 
Around 8,000 people are bitten by venomous snakes in the United States each year. On average, fewer than 15 snakebite deaths are reported.
Some rattlesnakes, especially the tropical species, have neurotoxic venom. A bite from these snakes can interfere with the function of the heart, paralyze the lungs, and shut down parts of the nervous system.
The Common Kingsnake (Lampropeltis getula), a constrictor, is famous for being largely immune to the venom of rattlesnakes and other vipers, and therefore rattlesnakes form part of this snake's natural diet in the wild.

## 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 hemorrhaging 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.

# Rattlesnakes as food
Rattlesnakes are also a popular food in some southwestern cuisines and are sometimes sold in speciality meat shops. It has a flavor that has been described as similar to chicken or frog legs and a chewy texture similar to alligator.

# Rattlesnakes in captivity
There are fairly obvious risks with private ownership of rattlesnakes. A bite can result in a large bill  for emergency medical care. Some jurisdictions outlaw the possession of venomous snakes. Where it is legal, some form of license or insurance policy may be required.

# Media