Reptiles
Kingsnake
Lampropeltis · also called king snake, milk snake
A kingsnake earns its name by eating other snakes — rattlesnakes included. It grips the rattler, throws its coils, and squeezes, and the venom the rattlesnake bites back with barely touches it. In several species the kingsnake also runs the opposite trick, wearing the red, black, and yellow rings of the deadly coral snake to scare off predators of its own.
Overview
Kingsnakes are the genus Lampropeltis, around 45 species across the Americas from Canada to Ecuador. They are medium-sized, glossy, non-venomous constrictors that live almost everywhere — prairie, forest, desert, swamp edge, gardens. Their diet is broad, but the defining habit is eating other snakes. The milk snakes are now classified within this same genus.
The snake-eater
Kingsnakes are ophiophagous — snake-eaters — and are largely immune to pit viper venom, carrying blood proteins that neutralise it. So a kingsnake can seize a striking rattlesnake, constrict it, and swallow it whole. Rattlesnakes recognise a kingsnake’s scent and shield their heads with a raised body loop rather than striking back. Kingsnakes also constrict with unusually high pressure, apparently killing by driving the prey’s blood pressure past what its heart can handle.
Mimicry and a milk myth
The scarlet kingsnake and several milk snakes are ringed in red, black, and yellow in close imitation of the venomous coral snake — Batesian mimicry that works where coral snakes actually live. The name “milk snake” comes from an old, biologically impossible belief that the snakes suckled milk from cows; they were really in the barn hunting rodents.
Status
Kingsnakes as a genus are Not Evaluated. Most are common and widespread, and several are popular, easy-to-keep pet snakes. But California and common kingsnake populations have dropped sharply in parts of their range for reasons not fully understood, with habitat loss, roads, and collection among the suspects.
Kingsnake: common questions
Can a kingsnake really eat a rattlesnake?
Yes, and it is one of the best-known things about them. A kingsnake will seize a rattlesnake, usually by the head or neck, throw coils around it, and constrict, and because the kingsnake is largely immune to pit viper venom the rattlesnake's defensive bites do little harm. Once the rattlesnake stops struggling the kingsnake swallows it whole, often a snake nearly as long as itself, working its jaws down the body. Rattlesnakes recognise the scent of kingsnakes and respond with a specific defensive behaviour, keeping the head low and away from the kingsnake while raising a body loop to shield the head and push the attacker away, rather than rattling and striking as they would at a mammal.
Are kingsnakes venomous or dangerous to people?
No. Kingsnakes have no venom at all; they kill by constriction. A kingsnake that is cornered or grabbed may musk, flatten its body, vibrate its tail, and bite, and a large one can give a bite that breaks the skin and, because kingsnake teeth angle backward, may hang on and need to be gently eased off, but this is a minor injury with no medical significance. They are generally considered good-tempered snakes, which is part of why they are common in the pet trade, and many wild ones calm quickly once they realise they are not being eaten.
Why do milk snakes and kingsnakes look like coral snakes?
Several kingsnakes, especially the scarlet kingsnake and some milk snakes, are ringed in red, black, and yellow or white in a pattern very close to that of the venomous coral snakes that share parts of their range. This is Batesian mimicry, in which a harmless species gains protection by resembling a dangerous one, because predators that have learned to avoid the coral snake's warning colours also avoid the mimic. The resemblance is closest where coral snakes are actually present and breaks down where they are absent, and rhymes such as red touch yellow, kill a fellow work for telling the true coral snake from its mimics, but only in the southeastern United States.
What is the difference between a kingsnake and a milk snake?
There is no longer a clean scientific line, because milk snakes are now classified within the same genus, Lampropeltis, as the kingsnakes. Traditionally, milk snake referred to the smaller, more slender, boldly banded forms, especially the widespread eastern milk snake and the tricolour milk snakes of Central and South America, while kingsnake referred to the larger, heavier-bodied species such as the common, California, and speckled kingsnakes, which are often blotched, striped, or speckled rather than ringed. In behaviour and biology they are much the same, all American constrictors that eat a wide range of prey including other snakes. The names are kept mostly by tradition and by the pet trade.