Coral snakes are a large group of elapidsnakes that can be subdivided into two distinct groups, Old World coral snakes and New World coral snakes. There are 16 species of Old World coral snake in three genera (Calliophis, Hemibungarus and Sinomicrurus), and over 65 recognized species of New World coral snakes in three genera (Leptomicrurus, Micruroides, and Micrurus). Genetic studies have found that the most basal lineages are Asian, indicating that the group originated in the Old World.
Coral snakes are most notable for their red, yellow/white, and black colored banding. (However, several nonvenomous species have similar coloration, including the scarlet snake, genus Cemophora, some of the kingsnakes and milk snakes, genus Lampropeltis, and the shovelnose snakes, genus Chionactis.) In some regions, the order of the bands distinguishes between the non-venomous mimics and the venomous coral snakes, inspiring some mnemonics — "Red on yellow, venom fellow; red on black, safe from attack." or "Red on black, venom lack; Red on yellow, killer fellow". Instead of poetry, remembering that yellow touches both other colors can indicate a cause for caution. However, this reliably applies only to coral snakes native to North America: Micrurus fulvius (Eastern or common coral snake), Micrurus tener (Texas coral snake), and Micruroides euryxanthus (Arizona coral snake), found in the southern and western United States. Coral snakes found in other parts of the world can have distinctly different patterns, have red bands touching black bands, have only pink and blue banding, or have no banding at all.
Most species of coral snake are small in size. North American species average around 3 feet (91 cm) in length, but specimens of up to 5 feet (150 cm) or slightly larger have been reported. Aquatic species have flattened tails acting as a fin, aiding in swimming.
Coral snake showing typically reclusive behavior of hiding under rotting wood. This one was over 30 inches (76 cm) long, but less than an inch (2.5 cm) across.
Coral snakes vary widely in their behavior, but most are very elusive, fossorial snakes which spend the vast majority of their time buried beneath the ground or in the leaf litter of a rainforest floor, coming to the surface only when it rains or during breeding season. Some species, like Micrurus surinamensis, are almost entirely aquatic and spend most of their lives in slow-moving bodies of water that have dense vegetation.
Like all elapid snakes, coral snakes possess a pair of small fangs to deliver their venom (some coral snakes are rear fanged). These fangs, which are enlarged and hollow, deliver their venom to their prey species, feeding mostly on smaller snakes, lizards, frogs, nestling birds, and rodents, etc. The venom takes time to take full effect.
Coral snakes have a tendency to hold on to a victim when biting, unlike vipers, which have retractable fangs and tend to prefer to strike, letting go immediately. Coral snakes are not aggressive or prone to biting and account for less than one percent of the number of snake bites each year in the United States.
New World coral snakes exist in the southern range of many temperate U.S. states. Coral snakes are found in scattered localities in the southern coastal plain from North Carolina to Louisiana, including all of Florida. They can be found in pine and scrub oak sandhill habitats in parts of this range but sometimes inhabit hardwood areas and pine flatwoods that undergo seasonal flooding.
There is controversy about the classification of the very similar Texas coral snake as a separate species. Its habitat, in Texas, Louisiana, Arkansas, and sometimes in Oklahoma due to floods in the Red River, is separated from the eastern habitat by the Mississippi River. The coral snake population is most dense in the southeast United States, but coral snakes have been spotted as far north as Kentucky.
The Arizona coral snake, clearly a separate species and genus, is found in central and southern Arizona, extreme southwestern New Mexico and southward to Sinaloa in western Mexico. It occupies arid and semiarid regions in many different habitat types including thornscrub, desert-scrub, woodland, grassland and farmland. It is found in the plains and lower mountain slopes from sea level to 5800 feet (1768 m); often found in rocky areas.
Danger to humans
New World coral snakes possess one of the most potent venoms of any North American snake. However, relatively few bites are recorded due to their reclusive nature and the fact they generally inhabit sparsely populated areas. According to the American National Institutes of Health, there are an average of 15–25 coral snake bites in the United States each year.
When confronted by humans, coral snakes will almost always attempt to flee, and bite only as a last resort. In addition, coral snakes have short fangs (proteroglyph dentition) that cannot penetrate thick leather clothing. Any skin penetration however, is a medical emergency that requires immediate attention. Coral snakes have a powerful neurotoxin that paralyzes the breathing muscles; mechanical or artificial respiration, along with large doses of antivenom, are often required to save a victim's life. There is usually only mild pain associated with a bite, but respiratory failure can occur within hours.
The bite of a coral snake may soon be more dangerous, in part because bites are so uncommon. Production of coral snake antivenom in the United States has ceased because it is not profitable. According to Pfizer, the owner of the company that used to make Coralmyn, it would take over $5–$10 million to put toward researching a new synthetic antivenom.[clarification needed] The cost was too large for the small number of cases presented each year. The current antivenom stock expired in 2010, after two consecutive expiration date extensions approved by the U.S. Food and Drug Administration. Foreign pharmaceutical manufacturers have produced other coral snake antivenoms, but the costs associated with licensing them in the United States have stalled availability (see above). Instituto Bioclon is developing a coral snake antivenom.
New World coral snakes serve as models for their Batesian mimics, false coral snakes, snake species whose venom is less toxic, as well as for many nonvenomous snake species that bear superficial resemblances to them. The role of coral snakes as models for Batesian mimics is supported by research showing that coral snake color patterns deter predators from attacking snake-shaped prey, and that in the absence of coral snakes, species hypothesized to mimic them are indeed attacked more frequently. Species that appear similar to coral snakes include:
^Slowinski, J. B., Boundy, J. and Lawson, R. (June 2001). "The Phylogenetic Relationships of Asian Coral Snakes (Elapidae: Calliophis and Maticora) Based on Morphological and Molecular Characters". Herpetologica57 (2): 233–245. JSTOR3893186.
^Brodie III, Edmund D. (1993). "Differential avoidance of coral snake banded patterns by free-ranging avian predators in Costa Rica". Evolution47 (1): 227–235. doi:10.2307/2410131.
^Brodie III, Edmund D., Moore, Allen J. (1995). "Experimental studies of coral snake mimicry: do snakes mimic millipedes?". Animal Behavior49 (2): 534–6. doi:10.1006/anbe.1995.0072.
^Pfennig, David W., Harcombe, William R., Pfennig, Karin S. (2001). "Frequncy-dependent Batesian mimicry". Nature410 (6826): 323. doi:10.1038/35066628. PMID11268195.
Boulenger, G.A. 1894. Catalogue of the Snakes in the British Museum (Natural History). Volume III., Containing the Colubridæ (Opisthoglyphæ and Proteroglyphæ)... Trustees of the British Museum (Natural History). (Taylor and Francis, Printers.) London. xiv + 727 pp. + Plates I.- XXV. (Elaps, 28 species, pp. 411–433 + Plate XX.)