The oldest Batesian trick in the book

Thursday, June 21, 2012
Rafe Brown

I’m proud to say, a few days ago at Camp Putik, I fell for the oldest trick I the book.  Million of years of evolution and selection pressures exerted by predators have produced many flavors of harmless animals which avoid predation by “mimicking” noxious, toxic, foul-tasting, or venomous co-distributed species.

Thus, back in Kansas, the harmless Regal Frittillary Butterfly (Speyeria idalia) are the same brilliant shades of red and brown as the toxic Monarch Butterfly (Danaus plexippus) and birds apparently cannot tell the difference and avoid eating them both.  The “mimic” benefits from the predator education on the part of the “model.”

Of course individuals of the mimic species (the harmless beneficiary of this trick) and the model (the species that packs the dangerous punch) are not actually engaged in conscious or active mimicry strategies.  Rather, it’s the predators who are born with innate, evolved, “instincts” to avoid brightly colored “warning” patterns that exert selection pressures by eating the harmless, drab colored individuals and avoiding the brightly colored ones.   Thus, the brightly colored variants disproportionately pass on a greater proportion of their genes to the next generation and, through time, the population as a whole becomes more brightly colored—and “mimics” the venomous model.  This all according to the famous Batesian Mimicry hypothesis of evolution of aposematic coloration.

In any case, last week as we enjoyed a few sips of rum late at night in camp, a brightly colored, banded snake crawled past our feet through the mud.  At a glance, I identified it as a Philippine coral snake (Calliophis intestinalis).  We very carefully captured it with sticks and gloves and only after it was in the bag did we realize we had before us the harmless example of Boie’s Dwarf Snake Calamaria lumbricoides.

I don't mess around with venomous reptiles.  In contrast to what you see on TV, most herpetologists who study venomous reptiles avoid touching subjects, never pin snakes behind the head and hold them in their hands, and in general, don't take chances.  In my book, every snake-wrangling cowboy made famous on the Discover Channel is living on borrowed time; eventually the odds will catch up with all of them. Given that handling venomous reptiles is part of my job description, I’m determined not to be a snakebite statistic…I lost a friend ten years ago to a krait bite in Burma, and I’d rather be safe than sorry.  Meanwhile, I have to admire the exquisitely precise coral snake mimicry achieved by Boie’s Dwarf Snake. —Rafe