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Table of Contents
The coral snake and milk snake are both found in North America, and look nearly identical. Why is this the case? Read about the coral snake versus the milk snake, how they are similar, and how they are different.
What are coral snakes?
Coral snakes are a huge group of dozens of snakes belonging to the family of elapid snakes. Almost all elapids are venomous. These snakes are iconic for their head flaps, which flare out when threatened—like the spectacled or king cobra. Elapids are found all over the world. A defining characteristic of this group are its reverse facing fangs, intended to inject venom into prey.
Coral snakes are broadly divided into two groups: the Old World coral snakes and the New World coral snakes. The Old World includes Eurasia, Africa, and Australasia. The New World is just North and South America. When Pangea broke up, some continents were still connected, but the Americas were the first to become entirely isolated. Since they have been alone for so long, their evolutionary history is completely different!
The fact that coral snakes have a distinct Old World–New World split means this group has been around for a long time indeed!
What are milk snakes?
The milk snake is a single species. The milk snake is a colubrid , which is an family of snakes with no particular defining characteristic. Colubrids are also found all over the world. Most colubrids are non-venomous.
Milk snakes are found over the United States, all along the East Coast and up to the southeastern extreme of Canada. Scientists have described 25 subspecies of the milk snake! There is much debate about whether this is a cryptic species complex . This is a group of subspecies that look so similar that they are confused as one species.
Why do coral and milk snakes look alike?
Milk snakes and coral snakes co-occur in the United States. Both are striped, with bars of red, yellow and black. Why should two species evolve to look so similar? The answer is because one is venomous, and one is not. Milk snakes are not the only coral snake mimic—there are 115, distributed all over the Americas.
Both groups are preyed on by similar predators, mainly birds of prey. While coral snakes do not usually pose a deadly danger to humans, coral snakes can kill or seriously injure predatory birds. Consequently, birds like motmots have an incredibly strong avoidance towards hunting these snakes; so strong that they may be born with this avoidance!
When nonvenomous or nontoxic animals develop a similarity to dangerous animals over many millions of years, they are known as mimics! This specific form of mimicry is known as Batesian mimicry, named after the scientist who described it. Although the coral snakes get very little out of this deal, this one sided partnership has evolved many times in many groups, suggesting it is evolutionarily stable. After all, if you were a bird, would you risk death for a snakey snack?
Flesch Kincaid Grade Level: 7.5
Flesch Kincaid Reading Ease: 62.2
Elapid: Snakes with reverse facing fangs, intended to inject venom into prey.
Colubrid: Typically non-venomous snakes, all of common ancestry
Cryptic species complex: A group of visually similar subspecies, all considered one species, but which may in fact be many distinct species