Let's keep this going!
I think a person would be hard-pressed to contradict the idea that a tricolored pattern disrupts a snake's outline, makes it difficult to track the animal during movement, and may even provide it some camouflage in certain instances. That said, mimicry, at least to some extent and form, is a pretty well supported idea. For a basic overview of the different mimicry hypotheses, the Wikipedia article provides satisfactory coverage.
The genus Micrurus ranges from the southern US to Argentina and generally consists of brightly ringed snakes well known for their aposematism. Throughout that range (and even outside of it, but still within the Americas - covered below), numerous other tricolored snakes, some mildly venomous and some harmless, occur. Tricolored members of the genus Lampropeltis share much of their range with Micrurus, and often mimic the later much better than they're given credit for. For example, L. triangulum and M. distans along Mexico's Pacific Coast, M. elegans along Mexico’s Caribbean lowlands, and M. mipartitus in Caribbean Central America. While our beloved Lampros do a pretty good job of mimicking Micrurus, they seem to be genetically constrained from becoming “perfect” mimics. It’s a mildly venomous genus known as Pliocercus which comes closest to Micrurus in color and pattern.
For some excellent reading, check out Allopatric Mimicry by Curt Eckerman, Coral Snake Mimicry: Does it Occur by Greene and McDiarmid, and various works by Harper and Pfennif, amongst others. I have .pdf copies if anyone has trouble finding them.
Here are a few question/answer sets from my understanding of the subject of Batesian mimicry (since that’s what the original thread appeared to focus on). Hopefully someone else will jump in here, too (Vinny?). There are no concrete answers, and this shouldn’t be a major surprise. There could be entire books written on this subject, so this’ll just be a skimming from the surface. The complexities of Nature are what make this so fun!
Q Why do Lampropeltis living outside the natural range of Micrurus often maintain a tricolored pattern?
A People often think of mammals as the ultimate predators of snakes. While it’s true that mammals do eat a lot of reptiles, birds are incredibly efficient predators of snakes, and in many instances are probably a snake’s greatest natural threat. Also, while most mammals see the world in a gray-scale, birds see colors very well. When the migration route of various predatory birds is mapped overlaying the distribution of tricolored Lampropeltis, it becomes readily noticeable that many birds wintering well within Micrurus range migrate North to breed/feed/summer in the Western US. Having a tricolored pattern would, then, convey an advantage to Lampropeltis living outside of the range of Micrurus but within the migratory range of snake predators which spend time with Micrurus.
Q How does a bite from a deadly snake “teach” birds to avoid brightly ringed snakes if the bird doesn’t live long enough to “learn” from its mistake?
A That’s not quite how it works. Here’s a quick-and-dirty overview on the mechanics of Batesian mimicry: Birds which are willing to take risks and attempt to feed on snakes displaying aposematic coloration are more likely to be weeded out of the reproductive population. Birds which avoid the brightly colored beasties don’t face that risk as much, so they have a genetic advantage which gets passed along to their offspring. Now, we can’t forget that there are other types of mimicry, too!
Q Why, then, aren’t the mimics better at mimicking the models?
A Well, some of them are pretty damn close! Check out some of the example I gave above! But, a species only has so much genetic plasticity within which to work. A species’ ancestors determine (for the most part) what tools it has to work with. Some animals, like the Pliocercus I talked about earlier, have greater genetic variability with regard to their pattern. Also, gene flow can temper the evolution of mimicry.
L. t. polyzona
