Snakes patterned with bright, alternating bands of red, black, and yellow are a classic example of Batesian mimicry. This occurs when a harmless species evolves to imitate the warning signals of a dangerous one, gaining protection from predators. In North America, several non-venomous snakes have evolved color patterns that closely resemble the highly venomous coral snake, creating significant confusion for people encountering them. Coral snakes belong to the Elapidae family, which includes cobras and mambas, and deliver a potent neurotoxic venom. Distinguishing the dangerously venomous species from its harmless mimics requires precise knowledge of the visual cues that differentiate them.
The Crucial Color Band Sequence
The most widely taught method for differentiating the venomous coral snake from its harmless look-alikes is to observe the precise order in which the colored bands meet on the snake’s body. This color sequence is the primary characteristic used to make an immediate distinction in the United States.
The venomous New World coral snakes display a pattern where the red bands are bordered directly by the yellow or white bands. This specific arrangement means that the red and yellow bands touch one another, creating a distinct visual warning.
The harmless mimics, such as the Scarlet Kingsnake (Lampropeltis elapsoides), reverse this order. On these non-venomous snakes, the red bands are bordered by the black bands, effectively separating the red from the yellow or white bands.
A common mnemonic device states that if “red touches yellow,” the snake is venomous, but if “red touches black,” the snake is harmless. This distinction is based on the general pattern of the tri-colored US species.
Identifying the Specific Species and Regional Context
The reliability of the red-and-yellow rule depends heavily on the geographical location of the encounter. Within the United States, the rule applies to the three native coral snake species: the Eastern Coral Snake (Micrurus fulvius), the Texas Coral Snake (Micrurus tener), and the Arizona or Sonoran Coral Snake (Micruroides euryxanthus). These species are found primarily in the southern and southwestern regions of the country.
The harmless snakes that mimic this pattern include the Scarlet Kingsnake and the Scarlet Snake (Cemophora coccinea), which often share the same habitats as the coral snakes. The existence of these mimics reinforces the effectiveness of the Batesian mimicry, as predators are consistently exposed to the warning coloration.
However, the mnemonic fails completely outside of the US, particularly in Central and South America, where dozens of other Micrurus species exist. Many of these species do not follow the red-touch-yellow pattern, and some venomous coral snakes in these regions have patterns where red bands touch black bands. Relying solely on the color rule outside of the US can lead to misidentification.
Morphological Differences Beyond Color
Beyond the color band sequence, several morphological characteristics can help confirm the identity of a snake, particularly when the coloration is ambiguous or the snake is coiled. The most noticeable secondary feature is the shape and color of the head.
Venomous coral snakes have a short, rounded, and blunt snout that is primarily black, extending back past the eyes. In contrast, the harmless Scarlet Kingsnake usually has a more elongated, pointed head, and its snout is often red or a color other than solid black.
The color pattern on the tail can offer another clue. The venomous coral snake frequently displays only black and yellow bands on its tail, with the red bands ending before the tail tip. The harmless mimics typically retain the tri-color pattern of red, black, and yellow all the way to the end of the tail.
Safe Practices During an Encounter
When encountering any banded snake resembling a coral snake, the safest action is non-engagement. Coral snakes are reclusive and spend much of their time underground or beneath leaf litter, making sightings rare. If a snake is spotted, maintaining a distance of at least six feet is recommended, regardless of whether the color pattern suggests it is a mimic or the venomous species.
A person should never attempt to capture, handle, or kill the snake. Coral snakes are not aggressive and will attempt to flee when confronted, only biting if they feel threatened.
If a bite does occur, it must be treated as a medical emergency requiring immediate attention. The neurotoxic venom affects the nervous system and can cause delayed symptoms like respiratory failure.
Contacting local animal control or emergency services is the appropriate step if a snake is found in a residential area. Attempting to identify the species by getting close enough to check the pupil shape or scale arrangement is unnecessarily dangerous and should be avoided. The safest practice is to assume any snake with this coloration might be the venomous coral snake and to simply leave it undisturbed.