User:Surreal/New Rattlesnake Edit
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27 species; see list of rattlesnake species and subspecies. |
Rattlesnakes are a group of venomous New World snakes formed from the genera, Crotalus and Sistrurus. There are about 30 species, with numerous subspecies.
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[edit] Physiology
All Rattlesnakes have a distinguishing body part unlike any other snake; a small segmented rattle at the end of their tails. It is composed of fibrous protein (like your finger nails). The rattle grows one segment with every annual shedding of the snake and the stub or matrix (pre-button of the first segment) is present at birth even if it isn’t visible to the naked eye. A Rattlesnake will shed about a week after birth and lose the initial stub, which is replaced by its first segment. Once the second shedding takes place and the snake has another segment the rattle becomes an effective audible warning system, designed to alert predators that the snake is dangerous. The sound is created when the snake vibrates its tail, causing each segment to bounce or rub against one another at the joints. Because the sound is produced from the rubbing of the dry segments rainfall or damp weather will temporarily disable the functionality of a snake’s rattle.
It is commonly believed you can tell the age of a Rattlesnake by the number of segments in the rattle, but since the rattle often breaks and diet/environmental factors can change the length of time between sheds, there is no truth to the claim.
Rattlesnakes are part of the Pit viper family and consequently retain the characteristic heat-sensitive pits between the eye and the nostril that enable them to effectively sense and seek their prey. The sensory organs function as advanced infra-red making the snake an effective nocturnal ambush-hunter. Rattlesnakes and other Pit vipers are also distinguishable by fangs in the upper part of the mouth that fold in, when not in use. When a pit viper attacks it, unfolds the fangs, strikes, and injects its venom. The venom is held in sacs on either side of the back of the jaws, fitting neatly in a triangular shaped head common among Rattlesnakes and other poisonous snakes.
[edit] Behavior
Some species in colder climates and at higher altitudes hibernate- or remain more dormant in winter. Rattlesnakes in cooler climates also prefer sun themselves on warm rocks while Rattlesnakes in hotter climates seek shelter and shade from searing temperatures.
Rattlesnakes feed on small mammals, reptiles, and birds by striking with its fangs and injecting venom; rather than constricting its prey. The bite stuns most small prey immediately but larger prey will flee until they succumb and the snake catches up.
Temperament and the relative threat of different species vary significantly. Some are relatively docile, while others are quite aggressive when challenged or threatened. Most snakes will flee from encounters with humans but some of the larger species like the Diamondback rattlesnake and the Mojave rattlesnake are responsible for several fatalities in the United States. Because Rattlesnakes that use their rattles around humans are often killed, there is speculation that some Rattlesnakes may have adapted and no longer give a warning sound when threatened. However it is pure speculation and it should be noted that a Rattlesnake’s first measure of defense is to remain quiet until it believes it is discovered.
[edit] Reproduction
Most Rattlesnakes mate in the spring and all species are ovoviviparous; meaning the young gestate within an egg that they use to feed from, but are born live. Broods, or the number of young born, typically vary by the size of the species. Smaller species typically birth 3-10 and larger species may birth 10-20. Mothers care for their young for 7 to 10 days (usually until the first shedding).
[edit] Toxicity
Rattlesnakes control the amount of venom they inject, generally delivering a full dose to prey, but less or none when striking defensively. But it is not uncommon for Rattlesnakes to strike repeatedly, especially if striking defensively.
Rattlesnakes are born with fully-functional fangs that deliver venom. Although capable of delivering less venom, some studies indicate that very young snakes have venoms that are more potent on a %conc basis than their adult counterparts. This makes the bite from the young just as dangerous as the bite from an adult snake, of the same species.
[edit] Venom
Most (but not all) Rattlesnake venom is primarily hemotoxic, meaning it is essentially digestive: destroying red blood cells, and skin tissue. The effectiveness and resulting damage of the poison depends on the species of the snake and the amount injected. Some species like the Pigmy rattlesnake produce a very mild venom which is toxic and can leave bruising or scarring but is not considered lethal. The Mojave Rattler on the other hand (and many of the larger, similar species), are considered lethal and some of the species have caused documented fatalities. The largest Rattlesnake, resulting in the most venom produced, is the Eastern Diamondback rattlesnake; and it is quite lethal even though it does not have the most potent venom.
Though uncommon, some Rattlesnakes (especially tropical species) have primarily neurotoxic venom. Though there is little visible sign of poisoning, neurotoxin venom can interfere with the function of the heart, lungs and other organs. Immediate treatment is essential for any victim of a neurotoxic bite.
[edit] Safety
Bites often occur when humans provoke or threaten (intentionally or unintentionally) a snake. The strike range of a Rattlesnake is typically a third of its body length. Boots and long pants are recommended for hiking in Rattlesnake areas. Remain observant and avoid potential encounters. Prevent pets or companions from provoking a snake. No matter the circumstance, always assume that venom has been injected when struck by a Rattlesnake and seek immediate help if bitten.
While not all Rattlesnakes have rattles—they can break off during the course of a snakes lifetime—they can always be identified as poisonous by their heads. Like all pit vipers, a Rattlesnake has cheeks that are wider than the rest of its body. Some observers describe this as a "diamond shaped head." In some regions such as the Western United States this feature is sufficient to determine whether a snake is poisonous. Other areas such as Florida contain poisonous snakes that are not pit vipers and do not share the same characteristics. So while every diamond headed snake is poisonous, some smooth headed snakes are also poisonous. Outdoor enthusiasts should memorize the characteristic markings of local species.
Quick medical attention is required for Rattlesnake bites, and typical treatment requires [antivenom|antivenin/anti-venom]] to prevent irreversible damage. It is recommended to keep the bitten body area below the heart level and to remain calm. It is not recommended by the U.S. Fish and Wildlife Service for untrained people to, make incisions at or around fang marks, or use tourniquets since the damage from this treatment may end up being worse than the bite itself would have caused.
Experienced health workers typically gauge poisoning in stages (0-5), from no evident venom to severely destructive amounts. The stages are equated to the amount of bruising and swelling around the fang marks and the speed with which bruising and swelling progress. In more severe cases (Stage 4 or 5) there may also be symptoms like lip-tingling, dizziness, bleeding, vomiting, or shock.
In the United States there is a recently-developed antivenin with the trade name Cro-Fab™, which is made from antibodies raised in sheep that have been inoculated with several different types of North American Pit viper venoms. This new antivenin is, highly purified, safer and more effective than the horse serum based antivenin it has essentially replaced.
[edit] See also
List of rattlesnake species and subspecies
[edit] References
- Manny Rubio; rattlesnake: A Portrait of a Predator; Smithsonian Institute Press; ISBN 1560988088 (hardcover, 1998)
- R. Burton, MD; Emergency Medicine. Lectures on Venom and Toxins. 1989.
- http://www.fws.gov/
- http://www.desertmuseum.org/books/rattlesnakes.html
[edit] External link
- rattlesnake Index (some photos)
- Desert USA article
- American International Rattlesnake Museum Albuquerque, New Mexico
