Coral snake vs kingsnake

Same colours, different order

Both snakes are ringed in red, black and yellow, and both live in the pine woods and hammocks of the south-eastern United States^1,2. The eastern coral snake has broad red and black rings separated by narrow yellow rings, so the red rings touch yellow, and the red rings usually carry black flecks¹. On the scarlet kingsnake the red and yellow rings are always separated by black, so red never touches yellow; in young kingsnakes the yellow rings may be white². That is what the rhyme “red touches yellow, kills a fellow; red touches black, venom lack” records^1,5.

The rhyme fits these two snakes in Florida most of the time, but unusual colour variants occasionally break it^1,2. It also works only in the United States: coral snakes in Mexico, Central America and South America may have red rings touching white or even black, so outside the US it must not be relied on at all⁵.

The snout

The second tell is the head. The coral snake has a rounded, blunt black snout followed by a broad yellow band behind the eyes¹. The scarlet kingsnake, like the other harmless look-alikes, has a red snout^1,2. Both have small heads barely wider than the neck and round pupils, so head shape and eye shape do not help^1,2.

Rings around the belly

On the coral snake the rings run right round the body, including the belly, and the tail is banded only in black and yellow¹. In Florida the scarlet kingsnake’s rings also encircle the body completely, but in Virginia many scarlet kingsnakes have rings that do not meet on the belly^2,4. The third ringed snake of the region, the harmless scarlet snake, has a more pointed red snout and rings that stop at the sides, leaving a plain cream belly^1,2.

Size and habits

The coral snake is the larger of the two: most adults are 51–76 cm long and the longest recorded was 120.7 cm¹. Most scarlet kingsnakes are 36–51 cm, with a record of about 74 cm, and hatchlings are only 13–18 cm^2,3. The kingsnake is a secretive, mostly nocturnal snake that hides under loose bark and in rotting logs and stumps, hunting skinks and small snakes^2,3. The coral snake is active by day, also spends most of its time under cover, and when disturbed it typically flees; if grabbed it bites readily and may chew, although chewing is not needed for it to inject venom¹. In a study of 39 people bitten by eastern coral snakes, most were bitten while handling the snake, and the commonest cause was mistaking it for a scarlet kingsnake⁶.

Why they look alike: Batesian mimicry

The scarlet kingsnake is a textbook Batesian mimic: a harmless species that copies a dangerous one so that predators which have learned to avoid the model avoid it too. Pfennig, Harcombe and Pfennig tested this in 2001 by setting out 1,200 life-size plasticine replicas of coral snakes and scarlet kingsnakes, inside the coral snake’s range in the Carolinas and beyond it in central North Carolina, where coral snakes do not live⁷. The replicas kept the marks of bites and scratches, and predators attacked the ringed models far more often where there were no coral snakes to teach them caution, which is just what Bates’s theory predicts⁷.

Later work showed that the resemblance is tuned by how common the model is. At the edge of the coral snake’s range, where coral snakes are rare, scarlet kingsnakes match them most precisely, because predators there can afford to attack any imperfect copy; deep inside the range, where coral snakes are common, even rough imitations are left alone⁸. In the Sandhills of North Carolina, where coral snakes disappeared around 1960, the kingsnakes went on evolving to look even more like them over the next 50 years, as the predators that still remembered coral snakes kept picking off the poorer mimics⁹.

If you are bitten or not sure

If a ringed snake bites someone and you cannot be certain it was a kingsnake, treat the bite as a coral snake bite^1,10. Coral snake bites may be painless with little swelling, and the effects can be delayed for hours before they progress: tingling, slurred speech, drooping eyelids, weakness and, at worst, paralysis of the breathing muscles¹⁰. Keep the person calm and still, remove rings and tight clothing near the bite, and get to hospital at once; every suspected bite is observed for at least 24 hours¹⁰. Do not use a tourniquet, ice, cutting or suction^10,12, and do not try to catch or kill the snake¹⁰. In the United States, Poison Help on 1-800-222-1222 gives free expert advice around the clock¹⁰, and the United States first-aid page has the full steps¹¹. These differences are not a safe basis for handling any snake; almost all coral snake bites happen when people deliberately handle them¹. Keep your distance from every snake you cannot identify.