Does 'Red Touches Yellow' Work? The Coral Snake Rhyme

What the rhyme says

The rhyme comes in many versions. The most familiar are “Red touches yellow, kills a fellow; red touches black, friend of Jack” and “Red on yellow, kill a fellow; red on black, venom lack.” All of them point to the same feature: look at the narrow bands on either side of each red ring.

On the venomous coral snakes of the United States, every red ring is bordered by yellow, or pale yellow to white in Arizona. On the harmless snakes that resemble them, each red band is bordered by black. The order of the colors, not the colors themselves, is what matters.

Where the rhyme works

The rhyme holds for all three coral snakes native to the US: the eastern coral snake of the Southeast, the Texas coral snake of Texas, Louisiana and Arkansas, and the smaller Sonoran coral snake of Arizona and New Mexico. It also sorts out the common native mimics.

East of the Mississippi River, a second clue helps: “Red face, I’m safe.” The eastern coral snake has a black snout followed by a broad yellow band, while the scarlet kingsnake and scarlet snake have red snouts. California has no coral snakes at all, so its red, black and white mountain kingsnakes are harmless wherever they are found. For a full side-by-side guide, see coral snake vs scarlet kingsnake.

Why it fails in Latin America

The United States holds only a tiny fraction of the world’s coral snakes. More than 80 species live in the Americas, from the southern US to Argentina, and most of them are tropical. Their patterns vary far more than the rhyme allows.

Many South American species, such as the South American coral snake (Micrurus lemniscatus) and the aquatic coral snake (Micrurus surinamensis), have black rings arranged in groups of three, called triads, so their red rings touch black. Other species have only two colors, such as black and red or black and white, with no yellow at all.

The mimics are just as varied. Tropical America has many harmless or mildly venomous “false coral snakes,” and some of them have red touching yellow. A traveler in Mexico, Costa Rica or Brazil who trusts the rhyme can therefore be wrong in both directions. In Asia and Africa the rhyme is meaningless: Old World coral snakes are often not red, yellow and black at all.

Exceptions even in the US

Within the US the rhyme is reliable for normal snakes, but nature produces exceptions. Texas coral snakes have been found that are albino, lack red pigment, or are almost entirely black, and odd-colored eastern coral snakes have also been recorded. On such a snake, the rhyme gives no answer or the wrong one.

The look-alikes vary too. Young scarlet kingsnakes are banded in red, black and white, and their pale bands turn various shades of yellow with age. Faded colors, mud, dim light and a snake moving through leaves all make ring order hard to judge. People also mix up the two halves of the rhyme, which is the worst possible mistake.

How the mimicry works

Harmless snakes look like coral snakes because of Batesian mimicry, in which a harmless species gains protection by resembling a dangerous one. Many birds and mammals avoid snakes with bright red, yellow and black rings, so a kingsnake dressed like a coral snake is attacked less often.

Field experiments in the southeastern US supported this idea. Researchers placed plasticine snake models in the woods and counted the bite marks left by predators. Ringed models were attacked less often than plain ones where coral snakes lived, but the advantage faded in areas without coral snakes. The scarlet kingsnake’s range extends well north of the coral snake’s, into places where its warning colors may protect it less.

A better rule: leave ringed snakes alone

No rhyme can replace distance. Most coral snake bites in the US happen when people pick up or handle the snake, often because they believed it was harmless or wanted a closer look. Coral snakes are shy, and simply leaving a ringed snake alone removes almost all of the risk, whatever its pattern.

If you see a red, yellow and black snake, watch it from a few steps away and let it move on. Teach children not to touch any snake, rather than teaching them a rhyme. If anyone is bitten, seek emergency medical help immediately: call 911. Symptoms of a coral snake bite can be delayed for hours, as explained in how venomous are coral snakes?