We recently posted a brief discussion of mimicry in which we mentioned the coral snake and it’s milk snake mimics. We wanted to post a brief follow-up with some photos we pulled off the web, as well as some quick additional observations about milk snakes.
Coral snakes comprise a group of venomous snakes that include over 75 species worldwide, with the majority of the species occurring in the New World. For the most part coral snakes are red, yellow or white, and black, with their colors appearing in a series of bands extending the length of the body. In North America, the color order is typically yellow / red / yellow / black / yellow / red...and so on and so forth, as depicted in the picture on the right. Hence the saying "red on yellow kills a fellow," though please remember this only holds in North America!
Given that coral snakes are highly venomous, it stands to reason that over time potential predators have learned to recognize them and avoid them - at least in part by their bright colors and banding, one would presume. In one of the most striking examples of mimicry in the reptile kingdom, several species of non-venomous snakes have evolved to closely resemble the coral snake in color and pattern. Evolution has evidently advantaged these snakes that by chance variation have the coral snake’s appearance, despite the fact that they do not possess the coral snakes toxic venom. This would on the surface appear to be an example of Batesian mimicry.
The two snakes that jump to mind as the most obvious are several varieties of milk snake and the scarlet kingsnake. In these non-venomous species, the colors and banding - red, yellow, and black - are virtually identical to those of the coral snake. Only the order is different, with the color sequence red / black / yellow / black / red...and so on an so forth. The saying here? “Red on black, venom lack!”
As can be seen above, these two snakes look nearly identical, aside from the fact the order of color is different. We should note here as well that banding on snakes is widely considered to be a protective trait. Try picking up a fast moving banded snake off the ground and you'll see why (hint: creates an optical illusion).
Interestingly, this is not the only example of mimicry in milk snakes. Eastern milk snakes not only resemble copperheads, they also apparently share several behavioral characteristics with copperheads as well. This helps them avoid predation from most of their likely predators, but unfortunately some confused humans have been known to kill Eastern milk snakes in a case of mistaken identity. It would appear no defense is 100% perfect!
The important thing to remember about the process of mimicry is that it works through natural selection and variation, not a conscious decision on the part of the “mimics” to copy the “models.”