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What Is the Key When Identifying Coral Snakes?

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“If red touches yellow, it kills a fellow. If red touches black, it's a friend of Jack”. The common, ages-old rhyme allegedly helps to distinguish between the venomous coral snake and several of the snake's harmless lookalikes. Unfortunately, this rhyme is not an accurate method for distinguishing between the two groups in all geographic areas.

Taxonomy and Classification

The taxonomy and classification of coral snakes is disputed. According to The Reptile Database, the common name “coral snake” applies to at least 91 species of snake worldwide. Disputing these numbers, a 2001 paper published in “Herpteologica,” authored by Jorge da Silva and Jack W. Sites, lists 120 named species, subspecies and geographic races within one coral snake lineage: the genus Micrurus. Despite the disparate descriptions of the lower taxa, scientists largely agree on the broad evolutionary patterns of the group. Coral snakes are elapids, relatives of cobras. In the Americas, two lineages exist, the large genus Micrurus, containing 84 species, and the genus Micruroides, which contains only one species: the Arizona coral snake (Micruroides euryxanthus). In Asia, the genus Calliophis contains about 12 species, though the genus is broken into several genera by some authors.

Coral Snake Biology

Coral snakes have relatively small, fixed fangs at the fronts of their mouths. Venom glands supply primarily neurotoxic venom to the fangs. In at least one species, the blue coral snake of Malaysia (Calliophis bivirgatus), the venom glands are enormous, extending past the head as far as one-third of the length down the snakes’ body. Coral snakes display bright yellow, red, orange or even blue markings. The markings are generally thought to provide aposematic, or warning, coloration, though some scientists hypothesize that the markings may also serve a cryptic function, helping them to hide from colorblind predators. When a predator confronts a coral snake, the coral snake responds by trying to escape, hiding his head, using his tail as a decoy, musking, everting his cloaca, everting his hemipenes or biting. Coral snakes chiefly prey on other snakes, though they occasionally consume small lizards.

Dangerous vs. Harmless

Many snake species share similar colors and patterns with sympatric coral snakes. According to Jay M. Savage and Joseph B. Slowinski, in a 2008 paper published in the “Biological Journal of the Linnean Society,” at least 115 species of harmless or mildly venomous species resemble New World coral snakes. It is widely thought that this is a form of Batesian mimicry; the dangerous coral snakes serve as a models for the less dangerous mimics, which benefit by resembling the deadly coral snakes. No universal criteria exist that make easy differentiation possible -- though the common rhyme does effectively distinguish the Eastern coral snakes from their sympatric mimics, the rhyme fails with western and South American groups. The colors and markings of coral snakes and their mimics vary over their range.

U.S Species

Three species are found north of the Mexican border: the Eastern coral snake (Micrurus fulvious), the Texas coral snake (Micrurus ) and the Arizona coral snake (Micruroides ). The eastern and Texas species are largely similar looking; in fact, they were only recently split into two species. The Arizona coral has bright colors as opposed to the muted or dark-tinged colors of the other two species. All three species have black snouts, but this fact does not provide positive identification.